1 OCAF {#occt_user_guides__ocaf}
2 ========================
6 @section occt_ocaf_1 Introduction
8 This manual explains how to use the Open CASCADE Application Framework (OCAF).
9 It provides basic documentation on using OCAF. For advanced information on OCAF
10 and its applications, see our <a href="http://www.opencascade.com/content/tutorial-learning">E-learning & Training</a> offerings.
12 @subsection occt_ocaf_1_1 Purpose of OCAF
14 OCAF (the Open CASCADE Application Framework) is an easy-to-use platform for rapidly developing
15 sophisticated domain-specific design applications.
16 A typical application developed using OCAF deals with two or three-dimensional (2D or 3D) geometric modeling
17 in trade-specific Computer Aided Design (CAD) systems, manufacturing or analysis applications,
18 simulation applications or illustration tools.
20 Developing a design application requires addressing many technical aspects.
21 In particular, given the functional specification of your application, you must at least:
23 * Design the architecture of the application— definition of the software components and the way they cooperate;
24 * Define the data model able to support the functionality required — a design application operates on data maintained during the whole end-user working session;
25 * Structure the software in order to:
26 * synchronize the display with the data — commands modifying objects must update the views;
27 * support generalized undo-redo commands — this feature has to be taken into account very early in the design process;
28 * Implement the function for saving the data — if the application has a long life cycle, the compatibility of data between versions of the application has to be addressed;
29 * Build the application user interface.
31 Architectural guidance and ready-to-use solutions provided by OCAF offer you the following benefits:
32 * You can concentrate on the functionality specific for your application;
33 * The underlying mechanisms required to support the application are already provided;
34 * The application can be rapidly be prototyped thanks to the coupling the other Open CASCADE Technology modules;
35 * The final application can be developed by industrializing the prototype — you don't need to restart the development from scratch.
36 * The Open Source nature of the platform guarantees the long-term usefulness of your development.
38 OCAF is much more than just one toolkit among many in the CAS.CADE Object Libraries. Since it can handle any data and algorithms in these libraries -- be it modeling algorithms, topology or geometry -- OCAF is their logical supplement.
40 The table below contrasts the design of a modeling application using object libraries alone and using OCAF.
42 **Table 1: Services provided by OCAF**
44 |Development tasks |Comments | Without OCAF | With OCAF |
45 |------------------:|---------:|---------------:|-----------:|
46 |Creation of geometry| Algorithm Calling the modeling libraries | To be created by the user | To be created by the user|
47 | Data organization | Including specific attributes and modeling process | To be created by the user | Simplified|
48 | Saving data in a file | Notion of document | To be created by the user | Provided |
49 | Document-view management | | To be created by the user | Provided |
50 | Application infrastructure | New, Open, Close, Save and Save As File menus | To be created by the user | Provided |
51 | Undo-Redo | Robust, multi-level | To be created by the user | Provided |
52 | Application-specific dialog boxes | | To be created by the user | To be created by the user |
54 OCAF uses other modules of Open CASCADE Technology — the Shape is implemented with the geometry supported by the <a href="#user_guides__modeling_data">Modeling Data</a> module and the viewer is the one provided with the <a href="#user_guides__visualization">Visualization</a> module. Modeling functions can be implemented using the <a href="#user_guides__modeling_algos">Modeling Algorithms</a> module.
56 The relationship between OCAF and the Open CASCADE Technology (**OCCT**) Object Libraries can be seen in the image below.
58 @figure{/user_guides/ocaf/images/ocaf_image003.svg, "OCCT Architecture"}
60 In the image, the OCAF (Open CASCADE Application Framework) is shown with black rectangles and OCCT Object Libraries required by OCAF are shown with white rectangles.
62 The subsequent chapters of this document explain the concepts and show how to use the services of OCAF.
64 @subsection occt_ocaf_1_2 Architecture Overview
66 OCAF provides you with an object-oriented Application-Document-Attribute model consisting of C++ class libraries.
68 @image html ocaf_wp_image003.png "The Application-Document-Attribute model"
69 @image latex ocaf_wp_image003.png "The Application-Document-Attribute model"
71 @subsubsection occt_ocaf_1_2_1 Application
73 The *Application* is an abstract class in charge of handling documents during the working session, namely:
74 * Creating new documents;
75 * Saving documents and opening them;
76 * Initializing document views.
78 @subsubsection occt_ocaf_1_2_2 Document
80 The document, implemented by the concrete class *Document*, is the container for the application data. Documents offer access to the data framework and serve the following purposes:
82 * Manage the notification of changes
83 * Update external links
84 * Manage the saving and restoring of data
85 * Store the names of software extensions.
86 * Manage command transactions
87 * Manage Undo and Redo options.
89 Each document is saved in a single flat ASCII file defined by its format and extension (a ready-to-use format is provided with OCAF).
91 Apart from their role as a container of application data, documents can refer to each other; Document A, for example, can refer to a specific label in Document B. This functionality is made possible by means of the reference key.
93 @subsubsection occt_ocaf_1_2_3 Attribute
95 Application data is described by **Attributes**, which are instances of classes derived from the *Attribute* abstract class, organized according to the OCAF Data Framework.
97 The @ref occt_ocaf_3 "OCAF Data Framework" references aggregations of attributes using persistent identifiers in a single hierarchy. A wide range of attributes come with OCAF, including:
99 * @ref occt_ocaf_6 "Standard attributes" allow operating with simple common data in the data framework (for example: integer, real, string, array kinds of data), realize auxiliary functions (for example: tag sources attribute for the children of the label counter), create dependencies (for example: reference, tree node)....;
100 * @ref occt_ocaf_5 "Shape attributes" contain the geometry of the whole model or its elements including reference to the shapes and tracking of shape evolution;
101 * Other geometric attributes such as **Datums** (points, axis and plane) and **Constraints** (*tangent-to, at-a-given-distance, from-a-given-angle, concentric,* etc.)
102 * User attributes, that is, attributes typed by the application
103 * @ref occt_ocaf_7 "Visualization attributes" allow placing viewer information to the data framework, visual representation of objects and other auxiliary visual information, which is needed for graphical data representation.
104 * @ref occt_ocaf_8 "Function services" — the purpose of these attributes is to rebuild objects after they have been modified (parameterization of models). While the document manages the notification of changes, a function manages propagation of these changes. The function mechanism provides links between functions and calls to various algorithms.
106 In addition, application-specific data can be added by defining new attribute classes; naturally, this changes the standard file format. The only functions that have to be implemented are:
107 * Copying the attribute
108 * Converting it from and persistent data storage
110 @subsection occt_ocaf_1_3 Reference-key model
112 In most existing geometric modeling systems, the data are topology driven.
113 They usually use a boundary representation (BRep), where geometric models
114 are defined by a collection of faces, edges and vertices,
115 to which application data are attached. Examples of data include:
119 * information that a particular edge is blended.
121 When the geometric model is parameterized, that is, when you can change
122 the value of parameters used to build the model (the radius of a blend, the thickness of a rib, etc.),
123 the geometry is highly subject to change.
124 In order to maintain the attachment of application data, the geometry must be distinguished from other data.
126 In OCAF, the data are reference-key driven. It is a uniform model in which reference-keys
127 are the persistent identification of data. All **accessible** data, including the geometry,
128 are implemented as attributes attached to reference-keys.
129 The geometry becomes the value of the Shape attribute, just as a number is the value
130 of the Integer and Real attributes and a string that of the Name attribute.
132 On a single reference-key, many attributes can be aggregated;
133 the application can ask at runtime which attributes are available.
134 For example, to associate a texture to a face in a geometric model,
135 both the face and the texture are attached to the same reference-key.
137 @image html ocaf_image004.png "Topology driven versus reference-key driven approaches"
138 @image latex ocaf_image004.png "Topology driven versus reference-key driven approaches"
140 Reference-keys can be created in two ways:
142 * At programming time, by the application
143 * At runtime, by the end-user of the application (providing that you include this capability in the application)
145 As an application developer, you generate reference-keys in order to give semantics to the data.
146 For example, a function building a prism may create three reference-keys:
147 one for the base of the prism, a second for the lateral faces and a third for the top face.
148 This makes up a semantic built-in the application's prism feature.
149 On the other hand, in a command allowing the end-user to set a texture to a face he/she selects,
150 you must create a reference-key to the selected face
151 if it has not previously been referenced in any feature
152 (as in the case of one of the lateral faces of the prism).
154 When you create a reference-key to selected topological elements (faces, edges or vertices),
155 OCAF attaches to the reference-key information defining the selected topology — the Naming attribute.
156 For example, it may be the faces to which a selected edge is common to.
157 This information, as well as information about the evolution of the topology at each modeling step
158 (the modified, updated and deleted faces), is used by the naming algorithm to maintain the topology
159 attached to the reference-key. As such, on a parametrized model,
160 after modifying the value of a parameter, the reference-keys still address the appropriate faces,
161 even if their geometry has changed.
162 Consequently, you change the size of the cube shown in the figure above,
163 the user texture stay attached to the right face.
165 <b>Note</b> As Topological naming is based on the reference-key and attributes such as Naming
166 (selection information) and Shape (topology evolution information),
167 OCAF is not coupled to the underlying modeling libraries.
168 The only modeling services required by OCAF are the following:
170 * Each algorithm must provide information about the evolution of the topology
171 (the list of faces modified, updated and deleted by the algorithm)
172 * Exploration of the geometric model must be available
173 (a 3D model is made of faces bounded by close wires,
174 themselves composed by a sequence of edges connected by their vertices)
176 Currently, OCAF uses the Open CASCADE Technology modeling libraries.
178 To design an OCAF-based data model, the application developer is encouraged to aggregate
179 ready-to-use attributes instead of defining new attributes by inheriting from an abstract root class.
180 There are two major advantages in using aggregation rather than inheritance:
182 * As you don't implement data by defining new classes, the format of saved data
183 provided with OCAF doesn't change; so you don't have to write the Save and Open functions
184 * The application can query the data at runtime if a particular attribute is available
188 * OCAF is based on a uniform reference-key model in which:
189 * Reference-keys provide persistent identification of data;
190 * Data, including geometry, are implemented as attributes attached to reference-keys;
191 * Topological naming maintains the selected geometry attached to reference-keys in parametrized models;
192 * In many applications, the data format provided with OCAF doesn't need to be extended;
193 * OCAF is not coupled to the underlying modeling libraries.
196 @section occt_ocaf_3 The Data Framework
198 @subsection occt_ocaf_3_1 Data Structure
200 The OCAF Data Framework is the Open CASCADE Technology realization
201 of the reference-key model in a tree structure. It offers a single environment where data from different application components can be handled. This allows exchanging and modifying data simply, consistently, with a maximum level of information and stable semantics.
204 The building blocks of this approach are:
210 As it has been mentioned earlier, the first label in a framework is the root label of the tree. Each label has a tag expressed as an integer value, and a label is uniquely defined by an entry expressed as a list of tags from the root, 0:1:2:1, for example.
212 Each label can have a list of attributes, which contain data, and several attributes can be attached to a label. Each attribute is identified by a GUID, and although a label may have several attributes attached to it, it must not have more than one attribute of a single GUID.
214 The sub-labels of a label are called its children. Conversely, each label, which is not the root, has a father. Brother labels cannot share the same tag.
216 The most important property is that a label’s entry is its persistent address in the data framework.
218 @image html /user_guides/ocaf/images/ocaf_image005.png "A simple framework model"
219 @image latex /user_guides/ocaf/images/ocaf_image005.png "A simple framework model"
221 In this image the circles contain tags of the corresponding labels. The lists of tags are located under the circles. The root label always has a zero tag.
223 The children of a root label are middle-level labels with tags 1 and 3. These labels are brothers.
225 List of tags of the right-bottom label is "0:3:4": this label has tag 4, its father (with entry "0:3") has tag 3, father of father has tag 0 (the root label always has "0" entry).
227 @subsection occt_ocaf_3_2 Examples of a Data Structure
229 Let's have a look at the example:
231 @image html ocaf_wp_image007.png "The coffee machine"
232 @image latex ocaf_wp_image007.png "The coffee machine"
234 In the image the application for designing coffee machines first allocates
235 a label for the machine unit. It then adds sub-labels for the main features
236 (glass coffee pot, water receptacle and filter) which it refines as needed
237 (handle and reservoir of the coffee pot and spout of the reservoir).
239 You now attach technical data describing the handle — its geometry and color —
240 and the reservoir — its geometry and material.
241 Later on, you can modify the handle's geometry without changing its color —
242 both remain attached to the same label.
244 @image html ocaf_wp_image005.png "The data structure of the coffee machine"
245 @image latex ocaf_wp_image005.png "The data structure of the coffee machine"
247 The nesting of labels is key to OCAF. This allows a label to have its own structure
248 with its local addressing scheme which can be reused in a more complex structure.
249 Take, for example, the coffee machine. Given that the coffee pot's handle has a label of tag [1],
250 the entry for the handle in the context of the coffee pot only (without the machine unit) is [0:1:1].
251 If you now model a coffee machine with two coffee pots, one at the label [1],
252 the second at the label [4] in the machine unit,
253 the handle of the first pot would have the entry [0:1:1:1]
254 whereas the handle of the second pot would be [0:1:4:1].
255 This way, we avoid any confusion between coffee pot handles.
257 Another example is the application for designing table lamps. The first label is allocated to the lamp unit.
259 @image html /user_guides/ocaf/images/ocaf_image006.png
260 @image latex /user_guides/ocaf/images/ocaf_image006.png
262 The root label cannot have brother labels. Consequently, various lamps in the framework allocation correspond to the sub-labels of the root label. This allows avoiding any confusion between table lamps in the data framework. Different lamp parts have different material, color and other attributes, so a child label of the lamp with the specified tags is allocated for each sub-unit of the lamp:
264 * a lamp-shade label with tag 1
265 * a bulb label with tag 2
266 * a stem label with tag 3
268 Label tags are chosen at will. They are only identifiers of the lamp parts. Now you can refine all units: by setting geometry, color, material and other information about the lamp or its parts to the specified label. This information is placed into special attributes of the label: the pure label contains no data -- it is only a key to access data.
270 Remember that tags are private addresses without any meaning outside the data framework. It would, for instance, be an error to use part names as tags. These might change or be removed from production in next versions of the application, whereas the exact form of that part might be reused in your design, the part name could be integrated into the framework as an attribute.
272 So, after the user changes the lamp design, only corresponding attributes are changed, but the label structure is maintained. The lamp shape must be recreated by new attribute values and attributes of the lamp shape must refer to a new shape.
274 @image html /user_guides/ocaf/images/ocaf_image007.png
275 @image latex /user_guides/ocaf/images/ocaf_image007.png
278 The previous figure shows the table-lamps document structure: each child of the root label contains a lamp shape attribute and refers to the sub-labels, which contain some design information about corresponding sub-units.
280 The data framework structure allows to create more complex structures: each lamp label sub-label may have children labels with more detailed information about parts of the table lamp and its components.
282 Note that the root label can have attributes too, usually global attributes: the name of the document, for example.
284 @subsection occt_ocaf_3_3 Tag
286 A tag is an integer, which identifies a label in two ways:
288 * Relative identification
289 * Absolute identification.
291 In relative identification, a label’s tag has a meaning relative to the father label only. For a specific label, you might, for example, have four child labels identified by the tags 2, 7, 18, 100. In using relative identification, you ensure that you have a safe scope for setting attributes.
293 In absolute identification, a label’s place in the data framework is specified unambiguously by a colon-separated list of tags of all the labels from the one in question to the root of the data framework. This list is called an entry. *TDF_Tool::TagList* allows retrieving the entry for a specific label.
295 In both relative and absolute identification, it is important to remember that the value of an integer has no intrinsic semantics whatsoever. In other words, the natural sequence that integers suggest, i.e. 0, 1, 2, 3, 4 ... -- has no importance here. The integer value of a tag is simply a key.
297 The tag can be created in two ways:
300 * User-defined delivery
302 As the names suggest, in random delivery, the tag value is generated by the system in a random manner. In user-defined delivery, you assign it by passing the tag as an argument to a method.
304 @subsubsection occt_ocaf_3_3_1 Creating child labels using random delivery of tags
306 To append and return a new child label, you use *TDF_TagSource::NewChild*. In the example below, the argument *level2*, which is passed to *NewChild,* is a *TDF_Label*.
309 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
310 TDF_Label child1 = TDF_TagSource::NewChild (level2);
311 TDF_Label child2 = TDF_TagSource::NewChild (level2);
312 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
314 @subsubsection occt_ocaf_3_3_2 Creation of a child label by user delivery from a tag
316 The other way to create a child label from a tag is by user delivery. In other words, you specify the tag, which you want your child label to have.
318 To retrieve a child label from a tag which you have specified yourself, you need to use *TDF_Label::FindChild* and *TDF_Label::Tag* as in the example below. Here, the integer 3 designates the tag of the label you are interested in, and the Boolean false is the value for the argument *create*. When this argument is set to *false*, no new child label is created.
321 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
322 TDF_Label achild = root.FindChild(3,Standard_False);
323 if (!achild.IsNull()) {
324 Standard_Integer tag = achild.Tag();
326 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
328 @subsection occt_ocaf_3_4 Label
330 The tag gives a persistent address to a label. The label -- the semantics of the tag -- is a place in the data framework where attributes, which contain data, are attached. The data framework is, in fact, a tree of labels with a root as the ultimate father label.
332 Label can not be deleted from the data framework, so, the structure of the data framework that has been created can not be removed while the document is opened. Hence any kind of reference to an existing label will be actual while an application is working with the document.
334 @subsubsection occt_ocaf_3_4_1 Label creation
336 Labels can be created on any labels, compared with brother labels and retrieved. You can also find their depth in the data framework (depth of the root label is 0, depth of child labels of the root is 1 and so on), whether they have children or not, relative placement of labels, data framework of this label. The class *TDF_Label* offers the above services.
338 @subsubsection occt_ocaf_3_4_2 Creating child labels
340 To create a new child label in the data framework using explicit delivery of tags, use *TDF_Label::FindChild*.
343 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.cpp}
344 //creating a label with tag 10 at Root
345 TDF_Label lab1 = aDF->Root().FindChild(10);
347 //creating labels 7 and 2 on label 10
348 TDF_Label lab2 = lab1.FindChild(7);
350 TDF_Label lab3 = lab1.FindChild(2);
351 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
352 You could also use the same syntax but add the Boolean *true* as a value of the argument **create**. This ensures that a new child label will be created if none is found. Note that in the previous syntax, this was also the case since **create** is *true* by default.
355 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.cpp}
356 TDF_Label level1 = root.FindChild(3,Standard_True);
357 TDF_Label level2 = level1.FindChild(1,Standard_True);
358 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
359 @subsubsection occt_ocaf_3_4_3 Retrieving child labels
361 You can retrieve child labels of your current label by iteration on the first level in the scope of this label.
364 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.cpp}
367 for (TDF_ChildIterator it1 (current,Standard_False); it1.More(); it1.Next()) {
368 achild = it1.Value();
370 // do something on a child (level 1)
373 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
374 You can also retrieve all child labels in every descendant generation of your current label by iteration on all levels in the scope of this label.
375 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.cpp}
376 for (TDF_ChildIterator itall (current,Standard_True); itall.More(); itall.Next()) {
377 achild = itall.Value();
379 // do something on a child (all levels)
382 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
383 Using *TDF_Tool::Entry* with *TDF_ChildIterator* you can retrieve the entries of your current label’s child labels as well.
386 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.cpp}
387 void DumpChildren(const TDF_Label& aLabel)
389 TDF_ChildIterator it;
390 TCollection_AsciiString es;
391 for (it.Initialize(aLabel,Standard_True); it.More(); it.Next()){
392 TDF_Tool::Entry(it.Value(),es);
393 cout << as.ToCString() << endl;
396 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
397 @subsubsection occt_ocaf_3_4_4 Retrieving the father label
399 Retrieving the father label of a current label.
402 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.cpp}
403 TDF_Label father = achild.Father();
404 isroot = father.IsRoot();
405 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
407 @subsection occt_ocaf_3_5 Attribute
409 The label itself contains no data. All data of any type whatsoever -- application or non-application -- is contained in attributes. These are attached to labels, and there are different types for different types of data. OCAF provides many ready-to-use standard attributes such as integer, real, constraint, axis and plane. There are also attributes for topological naming, functions and visualization. Each type of attribute is identified by a GUID.
411 The advantage of OCAF is that all of the above attribute types are handled in the same way. Whatever the attribute type is, you can create new instances of them, retrieve them, attach them to and remove them from labels, "forget" and "remember" the attributes of a particular label.
413 @subsubsection occt_ocaf_3_5_1 Retrieving an attribute from a label
415 To retrieve an attribute from a label, you use *TDF_Label::FindAttribute*. In the example below, the GUID for integer attributes, and *INT*, a handle to an attribute are passed as arguments to *FindAttribute* for the current label.
418 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.cpp}
419 if(current.FindAttribute(TDataStd_Integer::GetID(),INT))
421 // the attribute is found
425 // the attribute is not found
427 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
428 @subsubsection occt_ocaf_3_5_2 Identifying an attribute using a GUID
430 You can create a new instance of an attribute and retrieve its GUID. In the example below, a new integer attribute is created, and its GUID is passed to the variable *guid* by the method ID inherited from *TDF_Attribute*.
433 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.cpp}
434 Handle(TDataStd_Integer) INT = new TDataStd_Integer();
435 Standard_GUID guid = INT->ID();
436 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
438 @subsubsection occt_ocaf_3_5_3 Attaching an attribute to a label
440 To attach an attribute to a label, you use *TDF_Label::Add*. Repetition of this syntax raises an error message because there is already an attribute with the same GUID attached to the current label.
442 *TDF_Attribute::Label* for *INT* then returns the label *attach* to which *INT* is attached.
445 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.cpp}
446 current.Add (INT); // INT is now attached to current
447 current.Add (INT); // causes failure
448 TDF_Label attach = INT->Label();
449 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
450 @subsubsection occt_ocaf_3_5_4 Testing the attachment to a label
452 You can test whether an attribute is attached to a label or not by using *TDF_Attribute::IsA* with the GUID of the attribute as an argument. In the example below, you test whether the current label has an integer attribute, and then, if that is so, how many attributes are attached to it. *TDataStd_Integer::GetID* provides the GUID argument needed by the method IsAttribute.
454 *TDF_Attribute::HasAttribute* tests whether there is an attached attribute, and *TDF_Tool::NbAttributes* returns the number of attributes attached to the label in question, e.g. *current*.
457 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.cpp}
458 // Testing of attribute attachment
460 if (current.IsA(TDataStd_Integer::GetID())) {
461 // the label has an Integer attribute attached
463 if (current.HasAttribute()) {
464 // the label has at least one attribute attached
465 Standard_Integer nbatt = current.NbAttributes();
466 // the label has nbatt attributes attached
468 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
469 @subsubsection occt_ocaf_3_5_5 Removing an attribute from a label
471 To remove an attribute from a label, you use *TDF_Label::Forget* with the GUID of the deleted attribute. To remove all attributes of a label, *TDF_Label::ForgetAll*.
474 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.cpp}
475 current.Forget(TDataStd_Integer::GetID());
476 // integer attribute is now not attached to current label
478 // current has now 0 attributes attached
479 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
480 @subsubsection occt_ocaf_3_5_6 Specific attribute creation
482 If the set of existing and ready to use attributes implementing standard data types does not cover the needs of a specific data presentation task, the user can build his own data type and the corresponding new specific attribute implementing this new data type.
484 There are two ways to implement a new data type: create a new attribute (standard approach), or use the notion of User Attribute by means of a combination of standard attributes (alternative way)
486 In order to create a new attribute in the standard way, create a class inherited from *TDF_Attribute* and implement all purely virtual and necessary virtual methods:
487 * **ID()** -- returns a unique GUID of a given attribute
488 * **Restore(attribute)** -- sets fields of this attribute equal to the fields of a given attribute of the same type
489 * **Paste(attribute, relocation_table)** -- sets fields of a given attribute equal to the field values of this attribute ; if the attribute has references to some objects of the data framework and relocation_table has this element, then the given attribute must also refer to this object .
490 * **NewEmpty()** -- returns a new attribute of this class with empty fields
491 * **Dump(stream)** -- outputs information about a given attribute to a given stream debug (usually outputs an attribute of type string only)
493 Methods *NewEmpty, Restore* and *Paste* are used for the common transactions mechanism (Undo/Redo commands). If you don’t need this attribute to react to undo/redo commands, you can write only stubs of these methods, else you must call the Backup method of the *TDF_Attribute* class every time attribute fields are changed.
495 To enable possibility to save / restore the new attribute in XML format, do the following:
496 1. Create a new package with the name Xml[package name] (for example *XmlMyAttributePackage*) containing class *XmlMyAttributePackage_MyAttributeDriver*. The new class inherits *XmlMDF_ADriver* class and contains the translation functionality: from transient to persistent and vice versa (see the realization of the standard attributes in the packages *XmlMDataStd*, for example). Add package method AddDrivers which adds your class to a driver table (see below).
497 2. Create a new package (or do it in the current one) with two package methods:
498 * *Factory*, which loads the document storage and retrieval drivers; and
499 * *AttributeDrivers*, which calls the methods AddDrivers for all packages responsible for persistence of the document.
500 3. Create a plug-in implemented as an executable (see example *XmlPlugin*). It calls a macro PLUGIN with the package name where you implemented the method Factory.
502 To enable possibility to save / restore the new attribute in binary format, do the following:
503 1. Create a new package with name <i> Bin[package name] </i> (for example *BinMyAttributePackage*) containing a class *BinMyAttributePackage_MyAttributeDriver*. The new class inherits *BinMDF_ADriver* class and contains the translation functionality: from transient to persistent and vice versa (see the realization of the standard attributes in the packages *BinMDataStd*, for example). Add package method *AddDrivers*, which adds your class to a driver table.
504 2. Create a new package (or do it in the current one) with two package methods:
505 * Factory, which loads the document storage and retrieval drivers; and
506 * AttributeDrivers, which calls the methods AddDrivers for all packages responsible for persistence of the document.
507 3. Create a plug-in implemented as an executable (see example *BinPlugin*). It calls a macro PLUGIN with the package name where you implemented the method Factory.
508 See @ref occt_ocaf_4_3_3 "Saving the document" and @ref occt_ocaf_4_3_4 "Opening the document from a file" for the description of document save/open mechanisms.
510 If you decided to use the alternative way (create a new attribute by means of *UAttribute* and a combination of other standard attributes), do the following:
511 1. Set a *TDataStd_UAttribute* with a unique GUID attached to a label. This attribute defines the semantics of the data type (identifies the data type).
512 2. Create child labels and allocate all necessary data through standard attributes at the child labels.
513 3. Define an interface class for access to the data of the child labels.
515 Choosing the alternative way of implementation of new data types allows to forget about creating persistence classes for your new data type. Standard persistence classes will be used instead. Besides, this way allows separating the data and the methods for access to the data (interfaces). It can be used for rapid development in all cases when requirements to application performance are not very high.
517 Let’s study the implementation of the same data type in both ways by the example of transformation represented by *gp_Trsf* class. The class *gp_Trsf* defines the transformation according to the type (*gp_TrsfForm*) and a set of parameters of the particular type of transformation (two points or a vector for translation, an axis and an angle for rotation, and so on).
519 1. The first way: creation of a new attribute. The implementation of the transformation by creation of a new attribute is represented in the @ref occt_ocaf_11 "Samples".
521 2. The second way: creation of a new data type by means of combination of standard attributes. Depending on the type of transformation it may be kept in data framework by different standard attributes. For example, a translation is defined by two points. Therefore the data tree for translation looks like this:
522 * Type of transformation <i>(gp_Translation)</i> as *TDataStd_Integer*;
523 * First point as *TDataStd_RealArray* (three values: X1, Y1 and Z1);
524 * Second point as *TDataStd_RealArray* (three values: X2, Y2 and Z2).
526 @image html /user_guides/ocaf/images/ocaf_image010.png "Data tree for translation"
527 @image latex /user_guides/ocaf/images/ocaf_image010.png "Data tree for translation"
529 If the type of transformation is changed to rotation, the data tree looks like this:
530 * Type of transformation <i>(gp_Rotation)</i> as *TDataStd_Integer*;
531 * Point of axis of rotation as *TDataStd_RealArray* (three values: X, Y and Z);
532 * Axis of rotation as *TDataStd_RealArray* (three values: DX, DY and DZ);
533 * Angle of rotation as *TDataStd_Real*.
535 @image html /user_guides/ocaf/images/ocaf_image011.png "Data tree for rotation"
536 @image latex /user_guides/ocaf/images/ocaf_image011.png "Data tree for rotation"
538 The attribute *TDataStd_UAttribute* with the chosen unique GUID identifies the data type. The interface class initialized by the label of this attribute allows access to the data container (type of transformation and the data of transformation according to the type).
540 @subsection occt_ocaf_3_6 Compound documents
542 As the identification of data is persistent, one document can reference data contained in another document,
543 the referencing and referenced documents being saved in two separate files.
545 Lets look at the coffee machine application again. The coffee pot can be placed in one document.
546 The coffee machine document then includes an *occurrence* — a positioned copy — of the coffee pot.
547 This occurrence is defined by an XLink attribute (the external Link)
548 which references the coffee pot of the first document
549 (the XLink contains the relative path of the coffee pot document and the entry of the coffee pot data [0:1] ).
551 @image html ocaf_wp_image006.png "The coffee machine compound document"
552 @image latex ocaf_wp_image006.png "The coffee machine compound document"
554 In this context, the end-user of the coffee machine application can open the coffee pot document,
555 modify the geometry of, for example, the reservoir, and overwrite the document without worrying
556 about the impact of the modification in the coffee machine document.
557 To deal with this situation, OCAF provides a service which allows the application to check
558 whether a document is up-to-date. This service is based on a modification counter included in each document:
559 when an external link is created, a copy of the referenced document counter is associated to the XLink
560 in the referencing document. Providing that each modification of the referenced document increments its own counter,
561 we can detect that the referencing document has to be updated by comparing the two counters
562 (an update function importing the data referenced by an XLink into the referencing document is also provided).
564 @subsection occt_ocaf_3_7 Transaction mechanism
566 The Data Framework also provides a transaction mechanism inspired from database management systems:
567 the data are modified within a transaction which is terminated either by a Commit
568 if the modifications are validated or by an Abort if the modifications are abandoned —
569 the data are then restored to the state it was in prior to the transaction.
570 This mechanism is extremely useful for:
572 * Securing editing operations (if an error occurs, the transaction is abandoned and the structure retains its integrity)
573 * Simplifying the implementation of the **Cancel** function (when the end-user begins a command,
574 the application may launch a transaction and operate directly in the data structure;
575 abandoning the action causes the transaction to Abort)
576 * Executing **Undo** (at commit time, the modifications are recorded in order to be able to restore the data to their previous state)
578 The transaction mechanism simply manages a backup copy of attributes.
579 During a transaction, attributes are copied before their first modification.
580 If the transaction is validated, the copy is destroyed.
581 If the transaction is abandoned, the attribute is restored to its initial value
582 (when attributes are added or deleted, the operation is simply reversed).
584 Transactions are document-centered, that is, the application starts a transaction on a document.
585 So, modifying a referenced document and updating one of its referencing documents requires
586 two transactions, even if both operations are done in the same working session.
589 @section occt_ocaf_4_ Standard Document Services
591 @subsection occt_ocaf_4_1 Overview
593 Standard documents offer ready-to-use documents containing a TDF-based data framework. Each document can contain only one framework.
595 The documents themselves are contained in the instantiation of a class inheriting from *TDocStd_Application*. This application manages the creation, storage and retrieval of documents.
597 You can implement undo and redo in your document, and refer from the data framework of one document to that of another one. This is done by means of external link attributes, which store the path and the entry of external links.
599 To sum up, standard documents alone provide access to the data framework. They also allow you to:
601 * Update external links
602 * Manage the saving and opening of data
603 * Manage the undo/redo functionality.
606 @subsection occt_ocaf_4_2 The Application
608 As a container for your data framework, you need a document, and your document must be contained in your application. This application will be a class inheriting from *TDocStd_Application*.
610 @subsubsection occt_ocaf_4_2_1 Creating an application
612 To create an application, use the following syntax.
614 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.cpp}
615 Handle(TDocStd_Application) app
616 = new MyApplication_Application ();
617 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
618 Note that *MyApplication_Application* is a class, which you have to create and which will inherit from *TDocStd_Application*.
620 @subsubsection occt_ocaf_4_2_2 Creating a new document
622 To the application which you declared in the previous example (4.2.1), you must add the document *doc* as an argument of *TDocStd_Application::NewDocument*.
624 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.cpp}
625 Handle(TDocStd_Document) doc;
626 app->NewDocument("NewDocumentFormat", doc);
627 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
629 @subsubsection occt_ocaf_4_2_3 Retrieving the application to which the document belongs
631 To retrieve the application containing your document, you use the syntax below.
633 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.cpp}
634 app = Handle(TDocStd_Application)::DownCast
635 (doc->Application());
636 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
637 @subsection occt_ocaf_4_3 The Document
639 The document contains your data framework, and allows you to retrieve this framework, recover its main label, save it in a file, and open or close this file.
641 @subsubsection occt_ocaf_4_3_1 Accessing the main label of the framework
643 To access the main label in the data framework, you use *TDocStd_Document::Main* as in the example below. The main label is the first child of the root label in the data framework, and has the entry 0:1.
645 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.cpp}
646 TDF_Label label = doc->Main();
647 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
648 @subsubsection occt_ocaf_4_3_2 Retrieving the document from a label in its framework
650 To retrieve the document from a label in its data framework, you use *TDocStd_Document::Get* as in the example below. The argument *label* passed to this method is an instantiation of *TDF_Label*.
651 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.cpp}
652 doc = TDocStd_Document::Get(label);
653 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
655 @subsubsection occt_ocaf_4_3_3 Saving the document
657 If in your document you use only standard attributes (from the packages *TDF, TDataStd, TNaming, TFunction, TPrsStd* and *TDocStd*), you just do the following steps:
659 * In your application class (which inherits class *TDocStd_Application*) implement two methods:
660 + Formats (TColStd_SequenceOfExtendedString& theFormats), which append to a given sequence <i>\<theFormats\></i> your document format string, for example, "NewDocumentFormat" -- this string is also set in the document creation command
661 + ResourcesName(), which returns a string with a name of resources file (this file contains a description about the extension of the document, storage/retrieval drivers GUIDs...), for example, "NewFormat"
662 * Create the resource file (with name, for example, "NewFormat") with the following strings:
665 formatlist:NewDocumentFormat
666 NewDocumentFormat: New Document Format Version 1.0
667 NewDocumentFormat.FileExtension: ndf
668 NewDocumentFormat.StoragePlugin: bd696000-5b34-11d1-b5ba-00a0c9064368
669 NewDocumentFormat.RetrievalPlugin: bd696001-5b34-11d1-b5ba-00a0c9064368
670 NewDocumentFormatSchema: bd696002-5b34-11d1-b5ba-00a0c9064368
671 NewDocumentFormat.AttributeStoragePlugin:57b0b826-d931-11d1-b5da-00a0c9064368
672 NewDocumentFormat.AttributeRetrievalPlugin:57b0b827-d931-11d1-b5da-00a0c9064368
675 * Copy the resource file "Plugin" from $CASROOT/src/StdResource
677 In order to set the paths for these files it is necessary to set the environments: *CSF_PluginDefaults* and *CSF_NewFormatDefaults*. For example, set the files in the directory *MyApplicationPath/MyResources*:
680 setenv CSF_PluginDefaults MyApplicationPath/MyResources
681 setenv CSF_NewFormatDefaults MyApplicationPath/MyResources
684 Once these steps are taken you may run your application, create documents and Save/Open them.
686 @subsubsection occt_ocaf_4_3_4 Opening the document from a file
688 To open the document from a file where it has been previously saved, you can use *TDocStd_Application::Open* as in the example below. The arguments are the path of the file and the document saved in this file.
690 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.cpp}
691 app->Open("/tmp/example.caf", doc);
692 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
694 @subsubsection occt_ocaf_4_3_5 Cutting, copying and pasting inside a document
696 To cut, copy and paste inside a document, use the class *TDF_CopyLabel*.
698 In fact, you must define a *Label*, which contains the temporary value of a cut or
699 copy operation (say, in <i> Lab_Clipboard</i>). You must also define two other labels:
701 * The data container (e.g. <i> Lab_source</i>)
702 * The destination of the copy (e.g. <i> Lab_ Target</i> )
705 Copy = copy (Lab_Source => Lab_Clipboard)
706 Cut = copy + Lab_Source.ForgetAll() // command clear the contents of LabelSource.
707 Paste = copy (Lab_Clipboard => Lab_target)
710 So we need a tool to copy all (or a part) of the content of a label and its sub-label,
711 to another place defined by a label.
715 TDF_IDFilter aFilter (Standard_False);
717 //Don't copy TDataStd_TreeNode attribute
719 aFilter.Ignore(TDataStd_TreeNode::GetDefaultTreeID());
720 aCopy.Load(aSource, aTarget); aCopy.UseFilter(aFilter); aCopy.Perform();
722 // copy the data structure to clipboard
724 return aCopy.IsDone(); }
727 The filter is used to forbid copying a specified type of attribute.
729 You can also have a look at the class *TDF_Closure*, which can be useful to determine the dependencies of the part you want to cut from the document.
731 @subsection occt_ocaf_4_4 External Links
733 External links refer from one document to another. They allow you to update the copy of data framework later on.
735 @image html /user_guides/ocaf/images/ocaf_image012.png "External links between documents"
736 @image latex /user_guides/ocaf/images/ocaf_image012.png "External links between documents"
738 Note that documents can be copied with or without a possibility of updating an external link.
740 @subsubsection occt_ocaf_4_4_1 Copying the document
742 #### With the possibility of updating it later
744 To copy a document with a possibility of updating it later, you use *TDocStd_XLinkTool::CopyWithLink*.
746 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.cpp}
747 Handle(TDocStd_Document) doc1;
748 Handle(TDocStd_Document) doc2;
750 TDF_Label source = doc1->GetData()->Root();
751 TDF_Label target = doc2->GetData()->Root();
752 TDocStd_XLinkTool XLinkTool;
754 XLinkTool.CopyWithLink(target,source);
755 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
757 Now the target document has a copy of the source document. The copy also has a link in order to update the content of the copy if the original changes.
759 In the example below, something has changed in the source document. As a result, you need to update the copy in the target document. This copy is passed to *TDocStd_XLinkTool::UpdateLink* as the argument *target*.
761 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.cpp}
762 XLinkTool.UpdateLink(target);
763 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
765 #### Without any link between the copy and the original
767 You can also create a copy of the document with no link between the original and the copy. The syntax to use this option is *TDocStd_XLinkTool::Copy*. The copied document is again represented by the argument *target*, and the original -- by *source.*
769 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.cpp}
770 XLinkTool.Copy(target, source);
772 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
775 @section occt_ocaf_5 OCAF Shape Attributes
776 @subsection occt_ocaf_5_1 Overview
778 A topological attribute can be seen as a hook into the topological structure. It is possible to attach data to define references to it.
780 OCAF shape attributes are used for topology objects and their evolution access. All topological objects are stored in one *TNaming_UsedShapes* attribute at the root label of the data framework. This attribute contains a map with all topological shapes used in a given document.
782 The user can add the *TNaming_NamedShape* attribute to other labels. This attribute contains references (hooks) to shapes from the *TNaming_UsedShapes* attribute and an evolution of these shapes. The *TNaming_NamedShape* attribute contains a set of pairs of hooks: to the *Old* shape and to a *New* shape (see the following figure). It allows not only to get the topological shapes by the labels, but also to trace the evolution of the shapes and to correctly update dependent shapes by the changed one.
784 If a shape is newly created, then the old shape of a corresponding named shape is an empty shape. If a shape is deleted, then the new shape in this named shape is empty.
786 @image html /user_guides/ocaf/images/ocaf_image013.png
787 @image latex /user_guides/ocaf/images/ocaf_image013.png
789 @subsection occt_ocaf_5_2 Shape attributes in data framework.
791 Different algorithms may dispose sub-shapes of the result shape at the individual labels depending on whether it is necessary to do so:
793 * If a sub-shape must have some extra attributes (material of each face or color of each edge). In this case a specific sub-shape is placed to a separate label (usually to a sub-label of the result shape label) with all attributes of this sub-shape.
794 * If the topological naming algorithm is needed, a necessary and sufficient set of sub-shapes is placed to child labels of the result shape label. As usual, for a basic solid and closed shells, all faces of the shape are disposed.
796 *TNaming_NamedShape* may contain a few pairs of hooks with the same evolution. In this case the topology shape, which belongs to the named shape is a compound of new shapes.
798 Consider the following example. Two boxes (solids) are fused into one solid (the result one). Initially each box was placed to the result label as a named shape, which has evolution PRIMITIVE and refers to the corresponding shape of the *TNaming_UsedShapes* map. The box result label has a material attribute and six child labels containing named shapes of Box faces.
800 @image html /user_guides/ocaf/images/ocaf_image014.png "Resulting box"
801 @image latex /user_guides/ocaf/images/ocaf_image014.png "Resulting box"
803 After the fuse operation a modified result is placed to a separate label as a named shape, which refers to the old shape (one of the boxes) and to the new shape resulting from the fuse operation, and has evolution MODIFY (see the following figure).
805 Named shapes, which contain information about modified faces, belong to the fuse result sub-labels:
806 * sub-label with tag 1 -- modified faces from box 1,
807 * sub-label with tag 2 -- modified faces from box 2.
809 @image html /user_guides/ocaf/images/ocaf_image015.png
810 @image latex /user_guides/ocaf/images/ocaf_image015.png
812 This is necessary and sufficient information for the functionality of the right naming mechanism: any sub-shape of the result can be identified unambiguously by name type and set of labels, which contain named shapes:
814 * face F1’ as a modification of face F11
815 * face F1’’ as generation of face F12
816 * edges as an intersection of two contiguous faces
817 * vertices as an intersection of three contiguous faces
819 After any modification of source boxes the application must automatically rebuild the naming entities: recompute the named shapes of the boxes (solids and faces) and fuse the resulting named shapes (solids and faces) that reference to the new named shapes.
821 @subsection occt_ocaf_5_3 Registering shapes and their evolution
823 When using TNaming_NamedShape to create attributes, the following fields of an attribute are filled:
825 * A list of shapes called the "old" and the "new" shapes A new shape is recomputed as the value of the named shape. The meaning of this pair depends on the type of evolution.
826 * The type of evolution, which is a term of the *TNaming_Evolution* enumeration used for the selected shapes that are placed to the separate label:
827 * PRIMITIVE -- newly created topology, with no previous history;
828 * GENERATED -- as usual, this evolution of a named shape means, that the new shape is created from a low-level old shape ( a prism face from an edge, for example );
829 * MODIFY -- the new shape is a modified old shape;
830 * DELETE -- the new shape is empty; the named shape with this evolution just indicates that the old shape topology is deleted from the model;
831 * SELECTED -- a named shape with this evolution has no effect on the history of the topology.
833 Only pairs of shapes with equal evolution can be stored in one named shape.
835 @subsection occt_ocaf_5_4 Using naming resources
837 The class *TNaming_Builder* allows creating a named shape attribute. It has a label of a future attribute as an argument of the constructor. Respective methods are used for the evolution and setting of shape pairs. If for the same TNaming_Builder object a lot of pairs of shapes with the same evolution are given, then these pairs would be placed in the resulting named shape. After the creation of a new object of the TNaming_Builder class, an empty named shape is created at the given label.
839 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.cpp}
840 // a new empty named shape is created at "label"
841 TNaming_Builder builder(label);
842 // set a pair of shapes with evolution GENERATED
843 builder.Generated(oldshape1,newshape1);
844 // set another pair of shapes with the same evolution
845 builder.Generated(oldshape2,newshape2);
846 // get the result - TNaming_NamedShape attribute
847 Handle(TNaming_NamedShape) ns = builder.NamedShape();
848 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
850 @subsection occt_ocaf_5_5 Reading the contents of a named shape attribute
852 You can use the method <i>TNaming_NamedShape::Evolution()</i> to get the evolution of this named shape and the method <i>TNaming_NamedShape::Get()</i> to get a compound of new shapes of all pairs of this named shape.
854 More detailed information about the contents of the named shape or about the modification history of a topology can be obtained with the following:
855 * *TNaming_Tool* provides a common high-level functionality for access to the named shapes contents:
856 * The method <i>GetShape(Handle(TNaming_NamedShape)) </i> returns a compound of new shapes of the given named shape;
857 * The method <i>CurrentShape(Handle(TNaming_NamedShape))</i> returns a compound of the shapes, which are latest versions of the shapes from the given named shape;
858 * The method <i>NamedShape(TopoDS_Shape,TDF_Label) </i> returns a named shape, which contains a given shape as a new shape. A given label is any label from the data framework -- it just gives access to it.
859 * *TNaming_Iterator* gives access to the named shape and hooks pairs.
861 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.cpp}
862 // create an iterator for a named shape
863 TNaming_Iterator iter(namedshape);
864 // iterate while some pairs are not iterated
866 // get the new shape from the current pair
867 TopoDS_Shape newshape = iter.NewShape();
868 // get the old shape from the current pair
869 TopoDS_Shape oldshape = iter.OldShape();
872 // go to the next pair
875 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
878 @subsection occt_ocaf_5_6 Topological naming
880 The Topological Naming mechanism is based on 3 components:
881 * History of the used modeling operation algorithm;
882 * Registering of the built result in Data Framework (i.e. loading the necessary elements of the extracted history in OCAF document);
883 * Selection / Recomputation of a "selected" sub-shape of the algorithm result.
885 To get the expected result the work of the three components should be synchronized and the rules of each component should be respected.
887 @subsubsection occt_ocaf_5_6_1 Algorithm history
889 The "correct" history of a used modeling operation serves the basis of naming mechanism. It should be provided by the algorithm supporting the operation. The history content depends on the type of the topological result. The purpose of the history is to provide all entities for consistent and correct work of the Selection / Recomputation mechanism. The table below presents expected types of entities depending on the result type.
891 | Result type | Type of sub-shapes to be returned by history of algorithm | Comments |
892 | :---------- | :-------------------------------------------------------- | :------- |
893 | Solid or closed shell | Faces | All faces |
894 | Open shell or single face | Faces and edges of opened boundaries only | All faces plus all edges of opened boundaries |
895 | Closed wire | Edges | All edges |
896 | Opened wire | Edges and ending vertexes | All edges plus ending vertexes of the wire |
897 | Edge | Vertexes | Two vertexes are expected |
898 | Compound or CompSolid | To be used consequentially the above declared rule applied to all sub-shapes of the first level | Compound/CompSolid to be explored level by level until any the mentioned above types will be met |
900 The history should return (and track) only elementary types of sub-shapes, i.e. Faces, Edges and Vertexes, while other so-called aggregation types: Compounds, Shells, Wires, are calculated by Selection mechanism automatically.
902 There are some simple exceptions for several cases. For example, if the Result contains a seam edge -- in conical, cylindrical or spherical surfaces -- this seam edge should be tracked by the history and in addition should be defined before the types. All degenerated entities should be filtered and excluded from consideration.
904 @subsubsection occt_ocaf_5_6_2 Loading history in data framework
906 All elements returned by the used algorithm according to the aforementioned rules should be put in the Data Framework (or OCAF document in other words) consequently in linear order under the so-called **Result Label**.
908 The "Result Label" is *TDF_label* used to keep the algorithm result *Shape* from *TopoDS* in *NamedShape* attribute. During loading sub-shapes of the result in Data Framework should be used the rules of chapter @ref occt_ocaf_5_3. These rules are also applicable for loading the main shape, i.e. the resulting shape produced by the modeling algorithm.
910 @subsubsection occt_ocaf_5_6_3 Selection / re-computation mechanism
912 When the Data Framework is filled with all impacted entities (including the data structures resulting from the current modeling operation and the data structures resulting from the previous modeling operations, on which the current operation depends) any sub-shape of the current result can be **selected**, i.e. the corresponding new naming data structures, which support this functionality, can be produced and kept in the Data Framework.
914 One of the user interfaces for topological naming is the class *TNaming_Selector*. It implements the above mentioned sub-shape "selection" functionality as an additional one. I.e. it can be used for:
915 * Storing the selected shape on a label -- its **Selection**;
916 * Accessing the named shape -- check the kept value of the shape
917 * Update of this naming -- recomputation of an earlier selected shape.
919 The selector places a new named shape with evolution **SELECTED** to the given label. The selector creates a **name** of the selected shape, which is a unique description (data structure) of how to find the selected topology using as resources:
920 * the given context shape, i.e. the main shape kept on **Result Label**, which contains a selected sub-shape,
924 After any modification of a context shape and update of the corresponding naming structure, it is necessary to call method *TNaming_Selector::Solve*. If the naming structure, i.e. the above mentioned **name**, is correct, the selector automatically updates the selected sub-shape in the corresponding named shape, else it fails.
926 @subsection occt_ocaf_5_7 Exploring shape evolution
928 The class *TNaming_Tool* provides a toolkit to read current data contained in the attribute.
930 If you need to create a topological attribute for existing data, use the method *NamedShape*.
932 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.cpp}
935 public: Standard_Boolean SameEdge (const Handle(CafTest_Line)& L1, const Handle(CafTest_Line)& L2);
938 Standard_Boolean CafTest_MyClass::SameEdge (const Handle(CafTest_Line)& L1, const Handle(CafTest_Line)& L2)
940 Handle(TNaming_NamedShape) NS1 = L1->NamedShape();
941 Handle(TNaming_NamedShape) NS2 = L2->NamedShape();
942 return BRepTools::Compare(NS1,NS2);
944 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
947 @subsection occt_ocaf_5_8 Example of topological naming usage
949 **Topological naming** is a mechanism of Open CASCADE aimed to keep reference to the selected shape. If, for example, we select a vertex of a solid shape and “ask” the topological naming to keep reference to this vertex, it will refer to the vertex whatever happens with the shape (translations, scaling, fusion with another shape, etc.).
951 Let us consider an example: imagine a wooden plate. The job is to drive several nails in it:
953 @figure{/user_guides/ocaf/images/ocaf_image020.png, "A nail driven in a wooden plate"}
955 There may be several nails with different size and position. A **Hammer** should push each **Nail** exactly in the center point of the top surface. For this the user does the following:
956 * Makes several Nails of different height and diameter (according to the need),
957 * Chooses (selects) the upper surface of each Nail for the Hammer.
959 The job is done. The application should do the rest -- the Hammer calculates a center point for each selected surface of the Nail and “strikes” each Nail driving it into the wooden plate.
961 What happens if the user changes the position of some Nails? How will the Hammer know about it? It keeps reference to the surface of each Nail. However, if a Nail is relocated, the Hammer should know the new position of the selected surface. Otherwise, it will “strike” at the old position (keep the fingers away!)…
963 Topological naming mechanism should help the Hammer to obtain the relocated surfaces. The Hammer “asks” the mechanism to “resolve” the selected shapes by calling method *TNaming_Selection::Solve()* and the mechanism “returns” the modified surfaces located at the new position by calling *TNaming_Selector::NamedShape()*.
965 The topological naming is represented as a “black box” in the example above. Now it is time to make the box a little more “transparent”.
967 The application contains 3 functions:
968 * **Nail** -- produces a shape representing a nail,
969 * **Translator** -- translates a shape along the wooden plate,
970 * **Hammer** -- drives the nail in the wooden plate.
972 Each function gives the topological naming some hints how to “re-solve” the selected sub-shapes:
973 * The Nail constructs a solid shape and puts each face of the shape into sub-labels:
975 @figure{/user_guides/ocaf/images/ocaf_image021.png, "Distribution of faces through sub-labels of the Nail"}
977 * The **Translator** moves a shape and registers modification for each face: it puts a pair: “old” shape -- “new” shape at a sub-label of each moving Nail. The “old” shape represents a face of the Nail at the initial position. The “new” shape -- is the same face, but at a new position:
979 @figure{/user_guides/ocaf/images/ocaf_image022.png, "Registration of relocation of faces of a Nail"}
982 * The Hammer selects a face of a Nail calling *TNaming_Selector::Select()*. This call makes a unique name for the selected shape. In our example, it will be a direct reference to the label of the top face of the Nail (Face 1).
983 * When the user moves a Nail along the wooden plate, the Translator registers this modification by putting the pairs: “old” face of the Nail -- new face of the Nail into its sub-labels.
984 * When the Hammer calls *TNaming::Solve()*, the topological naming “looks” at the unique name of the selected shape and tries to re-solve it:
985 * It finds the 1st appearance of the selected shape in the data tree -- it is a label under the Nail function *Face 1*.
986 * It follows the evolution of this face. In our case, there is only one evolution -- the translation: *Face 1* (top face) -- <i>Face 1’</i> (relocated top face). So, the last evolution is the relocated top face.
987 * Calling the method *TNaming_Selector::NamedShape()* the Hammer obtains the last evolution of the selected face -- the relocated top face.
991 P.S. Let us say a few words about a little more complicated case -- selection of a wire of the top face. Its topological name is an “intersection” of two faces. We remember that the **Nail** puts only faces under its label. So, the selected wire will represent an “intersection” of the top face and the conic face keeping the “head” of the nail. Another example is a selected vertex. Its unique name may be represented as an “intersection” of three or even more faces (depends on the shape).
994 @section occt_ocaf_6 Standard Attributes
996 @subsection occt_ocaf_6_1 Overview
998 Standard attributes are ready-to-use attributes, which allow creating and modifying attributes for many basic data types. They are available in the packages *TDataStd, TDataXtd* and *TDF*. Each attribute belongs to one of four types:
1000 * Geometric attributes;
1001 * General attributes;
1002 * Relationship attributes;
1003 * Auxiliary attributes.
1007 ### Geometric attributes
1009 * **Axis** -- simply identifies, that the concerned *TNaming_NamedShape* attribute with an axis shape inside belongs to the same label;
1010 * **Constraint** -- contains information about a constraint between geometries: used geometry attributes, type, value (if exists), plane (if exists), "is reversed", "is inverted" and "is verified" flags;
1011 * **Geometry** -- simply identifies, that the concerned *TNaming_NamedShape* attribute with a specified-type geometry belongs to the same label;
1012 * **Plane** -- simply identifies, that the concerned *TNaming_NamedShape* attribute with a plane shape inside belongs to the same label;
1013 * **Point** -- simply identifies, that the concerned *TNaming_NamedShape* attribute with a point shape inside belongs to the same label;
1014 * **Shape** -- simply identifies, that the concerned *TNaming_NamedShape* attribute belongs to the same label;
1015 * **PatternStd** -- identifies one of five available pattern models (linear, circular, rectangular, circular rectangular and mirror);
1016 * **Position** -- identifies the position in 3d global space.
1018 ### General attributes
1020 * **AsciiString** -- contains AsciiString value;
1021 * **BooleanArray** -- contains an array of Boolean;
1022 * **BooleanList** -- contains a list of Boolean;
1023 * **ByteArray** -- contains an array of Byte (unsigned char) values;
1024 * **Comment** -- contains a string -- the comment for a given label (or attribute);
1025 * **Expression** -- contains an expression string and a list of used variables attributes;
1026 * **ExtStringArray** -- contains an array of *ExtendedString* values;
1027 * **ExtStringList** -- contains a list of *ExtendedString* values;
1028 * **Integer** -- contains an integer value;
1029 * **IntegerArray** -- contains an array of integer values;
1030 * **IntegerList** -- contains a list of integer values;
1031 * **IntPackedMap** -- contains a packed map of integers;
1032 * **Name** -- contains a string -- the name of a given label (or attribute);
1033 * **NamedData** -- may contain up to 6 of the following named data sets (vocabularies): *DataMapOfStringInteger, DataMapOfStringReal, DataMapOfStringString, DataMapOfStringByte, DataMapOfStringHArray1OfInteger* or *DataMapOfStringHArray1OfReal*;
1034 * **NoteBook** -- contains a *NoteBook* object attribute;
1035 * **Real** -- contains a real value;
1036 * **RealArray** -- contains an array of real values;
1037 * **RealList** -- contains a list of real values;
1038 * **Relation** -- contains a relation string and a list of used variables attributes;
1039 * **Tick** -- defines a boolean attribute;
1040 * **Variable** -- simply identifies, that a variable belongs to this label; contains the flag *is constraint* and a string of used units ("mm", "m"...);
1041 * **UAttribute** -- attribute with a user-defined GUID. As a rule, this attribute is used as a marker, which is independent of attributes at the same label (note, that attributes with the same GUIDs can not belong to the same label).
1043 ### Relationship attributes
1045 * **Reference** -- contains reference to the label of its own data framework;
1046 * **ReferenceArray** -- contains an array of references;
1047 * **ReferenceList** -- contains a list of references;
1048 * **TreeNode** -- this attribute allows to create an internal tree in the data framework; this tree consists of nodes with the specified tree ID; each node contains references to the father, previous brother, next brother, first child nodes and tree ID.
1050 ### Auxiliary attributes
1052 * **Directory** -- high-level tool attribute for sub-labels management;
1053 * **TagSource** -- this attribute is used for creation of new children: it stores the tag of the last-created child of the label and gives access to the new child label creation functionality.
1055 All attributes inherit class *TDF_Attribute*, so, each attribute has its own GUID and standard methods for attribute creation, manipulation, getting access to the data framework.
1058 @subsection occt_ocaf_6_2 Services common to all attributes
1060 @subsubsection occt_ocaf_6_2_1 Accessing GUIDs
1062 To access the GUID of an attribute, you can use two methods:
1063 * Method *GetID* is the static method of a class. It returns the GUID of any attribute, which is an object of a specified class (for example, *TDataStd_Integer* returns the GUID of an integer attribute). Only two classes from the list of standard attributes do not support these methods: *TDataStd_TreeNode* and *TDataStd_Uattribute*, because the GUIDs of these attributes are variable.
1064 * Method *ID* is the method of an object of an attribute class. It returns the GUID of this attribute. Absolutely all attributes have this method: only by this identifier you can discern the type of an attribute.
1066 To find an attribute attached to a specific label, you use the GUID of the attribute type you are looking for. This information can be found using the method <i> GetID</i> and the method <i> Find</i> for the label as follows:
1069 Standard_GUID anID = MyAttributeClass::GetID();
1070 Standard_Boolean HasAttribute = aLabel.Find(anID,anAttribute);
1073 @subsubsection occt_ocaf_6_2_2 Conventional Interface of Standard Attributes
1075 It is usual to create standard named methods for the attributes:
1077 * Method *Set(label, [value])* is the static method, which allows to add an attribute to a given label. If an attribute is characterized by one value this method may set it.
1078 * Method *Get()* returns the value of an attribute if it is characterized by one value.
1079 * Method *Dump(Standard_OStream)* outputs debug information about a given attribute to a given stream.
1081 @subsection occt_ocaf_6_3 The choice between standard and custom attributes
1083 When you start to design an application based on OCAF, usually it is necessary to choose, which attribute will be used for allocation of data in the OCAF document: standard or newly-created?
1085 It is possible to describe any model by means of standard OCAF attributes.
1086 However, it is still a question if this description will be efficient in terms of memory and speed, and, at the same time, convenient to use.
1088 This depends on a particular model.
1090 OCAF imposes the restriction that only one attribute type may be allocated to one label.
1091 It is necessary to take into account the design of the application data tree.
1092 For example, if a label should possess several double values,
1093 it is necessary to distribute them through several child sub-labels or use an array of double values.
1095 Let us consider several boundary implementations of the same model in OCAF tree and analyze the advantages and disadvantages of each approach.
1098 @subsubsection occt_ocaf_6_2_3 Comparison and analysis of approaches
1100 Below are described two different model implementations:
1101 one is based on standard OCAF attributes and the other is based
1102 on the creation of a new attribute possessing all data of the model.
1104 A load is distributed through the shape. The measurements are taken at particular points defined by (x, y and z) co-ordinates. The load is represented as a projection onto X, Y and Z axes of the local co-ordinate system at each point of measurement. A matrix of transformation is needed
1105 to convert the local co-ordinate system to the global one, but this is optional.
1107 So, we have 15 double values at each point of measurement.
1108 If the number of such points is 100 000, for example, it means
1109 that we have to store 1 500 000 double values in the OCAF document.
1111 The first approach consists in using standard OCAF attributes.
1112 Besides, there are several variants of how the standard attributes may be used:
1113 * Allocation of all 1 500 000 double values as one array of double values attached to one label;
1114 * Allocation of values of one measure of load (15 values) as one array of double values and attachment of one point of measure to one label;
1115 * Allocation of each point of measure as an array of 3 double values attached to one label, the projection of load onto the local co-ordinate system axes as another array of 3 double values attached to a sub-label, and the matrix of projection (9 values) as the third array also attached to a sub-label.
1117 Certainly, other variants are also possible.
1119 @image html ocaf_tree_wp_image003.png "Allocation of all data as one array of double values"
1120 @image latex ocaf_tree_wp_image003.png "Allocation of all data as one array of double values"
1122 The first approach to allocation of all data represented as one array of double values
1123 saves initial memory and is easy to implement.
1124 But access to the data is difficult because the values are stored in a flat array.
1125 It will be necessary to implement a class with several methods giving access
1126 to particular fields like the measurement points, loads and so on.
1128 If the values may be edited in the application,
1129 it means that the whole array will be backed-up on each edition.
1130 The memory usage will increase very fast!
1131 So, this approach may be considered only in case of non-editable data.
1133 Let’s consider the allocation of data of each measurement point per label (the second case).
1134 In this case we create 100 000 labels -- one label for each measurement point
1135 and attach an array of double values to these labels:
1137 @image html ocaf_tree_wp_image004.png "Allocation of data of each measurement point as arrays of double values"
1138 @image latex ocaf_tree_wp_image004.png "Allocation of data of each measurement point as arrays of double values"
1140 Now edition of data is safer as far as memory usage is concerned.
1141 Change of value for one measurement point (any value: point co-ordinates, load, and so on)
1142 backs-up only one small array of double values.
1143 But this structure (tree) requires more memory space (additional labels and attributes).
1145 Besides, access to the values is still difficult and it is necessary
1146 to have a class with methods of access to the array fields.
1148 The third case of allocation of data through OCAF tree is represented below:
1150 @image html ocaf_tree_wp_image005.png "Allocation of data into separate arrays of double values"
1151 @image latex ocaf_tree_wp_image005.png "Allocation of data into separate arrays of double values"
1153 In this case sub-labels are involved and we can easily access the values of each measurement point,
1154 load or matrix. We don’t need an interface class with methods of access to the data
1155 (if it exists, it would help to use the data structure, but this is optional).
1157 On the one hand, this approach requires more memory for allocation of the attributes (arrays of double values).
1158 On the other hand, it saves memory during the edition of data
1159 by backing-up only the small array containing the modified data.
1160 So, if the data is fully modifiable, this approach is more preferable.
1162 Before making a conclusion, let’s consider the same model implemented through a newly created OCAF attribute.
1164 For example, we might allocate all data belonging to one measurement point as one OCAF attribute.
1165 In this case we implement the third variant of using the standard attributes (see picture 3),
1166 but we use less memory (because we use only one attribute instead of three):
1168 @image html ocaf_tree_wp_image006.png "Allocation of data into newly created OCAF attribute"
1169 @image latex ocaf_tree_wp_image006.png "Allocation of data into newly created OCAF attribute"
1171 The second variant of using standard OCAF attributes still has drawbacks:
1172 when data is edited, OCAF backs-up all values of the measurement point.
1174 Let’s imagine that we have some non-editable data.
1175 It would be better for us to allocate this data separately from editable data.
1176 Back-up will not affect non-editable data and memory will not increase so much during data edition.
1178 @subsubsection occt_ocaf_6_2_4 Conclusion
1180 When deciding which variant of data model implementation to choose,
1181 it is necessary to take into account the application response time,
1182 memory allocation and memory usage in transactions.
1184 Most of the models may be implemented using only standard OCAF attributes.
1185 Some other models need special treatment and require implementation of new OCAF attributes.
1188 @section occt_ocaf_7 Visualization Attributes
1190 @subsection occt_ocaf_7_1 Overview
1192 Standard visualization attributes implement the Application Interactive Services (see @ref occt_user_guides__visualization "Visualization User's Guide"). in the context of Open CASCADE Technology Application Framework. Standard visualization attributes are AISViewer and Presentation and belong to the TPrsStd package.
1194 @subsection occt_ocaf_7_2 Services provided
1196 @subsubsection occt_ocaf_7_2_1 Defining an interactive viewer attribute
1198 The class *TPrsStd_AISViewer* allows you to define an interactive viewer attribute. There may be only one such attribute per one data framework and it is always placed to the root label. So, it could be set or found by any label ("access label") of the data framework. Nevertheless the default architecture can be easily extended and the user can manage several Viewers per one framework by himself.
1200 To initialize the AIS viewer as in the example below, use method *Find*.
1202 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.cpp}
1203 // "access" is any label of the data framework
1204 Handle(TPrsStd_AISViewer) viewer = TPrsStd_AISViewer::Find(access)
1205 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1207 @subsection occt_ocaf_7_2_2 Defining a presentation attribute
1209 The class *TPrsStd_AISPresentation* allows you to define the visual presentation of document labels contents. In addition to various visual fields (color, material, transparency, *isDisplayed*, etc.), this attribute contains its driver GUID. This GUID defines the functionality, which will update the presentation every time when needed.
1211 @subsubsection occt_ocaf_7_2_3 Creating your own driver
1213 The abstract class TPrsStd_Driver allows you to define your own driver classes. Simply redefine the Update method in your new class, which will rebuild the presentation.
1215 If your driver is placed to the driver table with the unique driver GUID, then every time the viewer updates presentations with a GUID identical to your driver’s GUID, the *Update* method of your driver for these presentations must be called:
1216 @image html /user_guides/ocaf/images/ocaf_image016.png
1217 @image latex /user_guides/ocaf/images/ocaf_image016.png
1219 As usual, the GUID of a driver and the GUID of a displayed attribute are the same.
1221 @subsubsection occt_ocaf_7_2_4 Using a container for drivers
1223 You frequently need a container for different presentation drivers. The class *TPrsStd_DriverTable* provides this service. You can add a driver to the table, see if one is successfully added, and fill it with standard drivers.
1225 To fill a driver table with standard drivers, first initialize the AIS viewer as in the example above, and then pass the return value of the method *InitStandardDrivers* to the driver table returned by the method *Get*. Then attach a *TNaming_NamedShape* to a label and set the named shape in the presentation attribute using the method *Set*. Then attach the presentation attribute to the named shape attribute, and the *AIS_InteractiveObject*, which the presentation attribute contains, will initialize its drivers for the named shape. This can be seen in the example below.
1228 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.cpp}
1229 DriverTable::Get() -> InitStandardDrivers();
1230 // next, attach your named shape to a label
1231 TPrsStd_AISPresentation::Set(NS};
1232 // here, attach the AISPresentation to NS.
1233 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1236 @section occt_ocaf_8 Function Services
1238 Function services aggregate data necessary for regeneration of a model. The function mechanism -- available in the package *TFunction* -- provides links between functions and any execution algorithms, which take their arguments from the data framework, and write their results inside the same framework.
1240 When you edit any application model, you have to regenerate the model by propagating the modifications. Each propagation step calls various algorithms. To make these algorithms independent of your application model, you need to use function services.
1242 @image html /user_guides/ocaf/images/ocaf_image008.png "Document structure"
1243 @image latex /user_guides/ocaf/images/ocaf_image008.png "Document structure"
1245 Take, for example, the case of a modeling sequence made up of a box with the application of a fillet on one of its edges. If you change the height of the box, the fillet will need to be regenerated as well.
1247 @subsection occt_ocaf_8_1 Finding functions, their owners and roots
1249 The class *TFunction_Function* is an attribute, which stores a link to a function driver in the data framework. In the static table *TFunction_DriverTable* correspondence links between function attributes and drivers are stored.
1251 You can write your function attribute, a driver for such attribute, which updates the function result in accordance to a given map of changed labels, and set your driver with the GUID to the driver table.
1253 Then the solver algorithm of a data model can find the *Function* attribute on a corresponding label and call the *Execute* driver method to update the result of the function.
1255 @subsection occt_ocaf_8_2 Storing and accessing information about function status
1257 For updating algorithm optimization, each function driver has access to the *TFunction_Logbook* object that is a container for a set of touched, impacted and valid labels. Using this object a driver gets to know which arguments of the function were modified.
1259 @subsection occt_ocaf_8_3 Propagating modifications
1261 An application must implement its functions, function drivers and the common solver for parametric model creation. For example, check the following model:
1263 @image html /user_guides/ocaf/images/ocaf_image017.png
1264 @image latex /user_guides/ocaf/images/ocaf_image017.png
1266 The procedure of its creation is as follows:
1267 * create a rectangular planar face *F* with height 100 and width 200;
1268 * create prism *P* using face *F* as a basis;
1269 * create fillet *L* at the edge of the prism;
1270 * change the width of *F* from 200 to 300;
1271 * the solver for the function of face *F* starts;
1272 * the solver detects that an argument of the face *F* function has been modified;
1273 * the solver calls the driver of the face *F* function for a regeneration of the face;
1274 * the driver rebuilds face *F* and adds the label of the face *width* argument to the logbook as touched and the label of the function of face *F* as impacted;
1276 * the solver detects the function of *P* -- it depends on the function of *F*;
1277 * the solver calls the driver of the prism *P* function;
1278 * the driver rebuilds prism *P* and adds the label of this prism to the logbook as impacted;
1279 * the solver detects the function of *L* -- it depends on the function of *P*;
1280 * the solver calls the *L* function driver;
1281 * the driver rebuilds fillet *L* and adds the label of the fillet to the logbook as impacted.
1283 @section occt_ocaf_8a Example of Function Mechanism Usage
1285 @subsection occt_ocaf_8a_1 Introduction
1287 Let us describe the usage of the Function Mechanism of Open CASCADE Application Framework on a simple example.
1288 This example represents a "nail" composed by a cone and two cylinders of different radius and height:
1290 @image html ocaf_functionmechanism_wp_image003.png "A nail"
1291 @image latex ocaf_functionmechanism_wp_image003.png " A nail"
1293 These three objects (a cone and two cylinders) are independent,
1294 but the Function Mechanism makes them connected to each other and representing one object -- a nail.
1295 The object "nail" has the following parameters:
1297 * The position of the nail is defined by the apex point of the cone.
1298 The cylinders are built on the cone and therefore they depend on the position of the cone.
1299 In this way we define a dependency of the cylinders on the cone.
1300 * The height of the nail is defined by the height of the cone.
1301 Let’s consider that the long cylinder has 3 heights of the cone
1302 and the header cylinder has a half of the height of the cone.
1303 * The radius of the nail is defined by the radius of the cone.
1304 The radius of the long cylinder coincides with this value.
1305 Let’s consider that the header cylinder has one and a half radiuses of the cone.
1307 So, the cylinders depend on the cone and the cone parameters define the size of the nail.
1309 It means that re-positioning the cone (changing its apex point) moves the nail,
1310 the change of the radius of the cone produces a thinner or thicker nail,
1311 and the change of the height of the cone shortens or prolongates the nail.
1312 It is suggested to examine the programming steps needed to create a 3D parametric model of the "nail".
1314 @subsection occt_ocaf_8a_2 Step 1: Data Tree
1316 The first step consists in model data allocation in the OCAF tree.
1317 In other words, it is necessary to decide where to put the data.
1319 In this case, the data can be organized into a simple tree
1320 using references for definition of dependent parameters:
1328 + Position = "Cone" position translated for "Cone" height along Z;
1329 + Radius = "Cone" radius;
1330 + Height = "Cone" height multiplied by 3;
1332 + Position = "Long cylinder" position translated for "Long cylinder" height along Z;
1333 + Radius = "Long cylinder" radius multiplied by 1.5;
1334 + Height = "Cone" height divided by 2.
1336 The "nail" object has three sub-leaves in the tree: the cone and two cylinders.
1338 The cone object is independent.
1340 The long cylinder representing a "stem" of the nail refers to the corresponding parameters
1341 of the cone to define its own data (position, radius and height). It means that the long cylinder depends on the cone.
1343 The parameters of the head cylinder may be expressed through the cone parameters
1344 only or through the cone and the long cylinder parameters.
1345 It is suggested to express the position and the radius of the head cylinder
1346 through the position and the radius of the long cylinder, and the height
1347 of the head cylinder through the height of the cone.
1348 It means that the head cylinder depends on the cone and the long cylinder.
1350 @subsection occt_ocaf_8a_3 Step 2: Interfaces
1352 The interfaces of the data model are responsible for dynamic creation
1353 of the data tree of the represented at the previous step, data modification and deletion.
1355 The interface called *INail* should contain the methods for creation
1356 of the data tree for the nail, setting and getting of its parameters, computation, visualization and removal.
1358 @subsubsection occt_ocaf_8a_3_1 Creation of the nail
1360 This method of the interface creates a data tree for the nail at a given leaf of OCAF data tree.
1362 It creates three sub-leaves for the cone and two cylinders and allocates the necessary data (references at the sub-leaves of the long and the head cylinders).
1364 It sets the default values of position, radius and height of the nail.
1366 The nail has the following user parameters:
1367 * The position -- coincides with the position of the cone
1368 * The radius of the stem part of the nail -- coincides with the radius of the cone
1369 * The height of the nail -- a sum of heights of the cone and both cylinders
1371 The values of the position and the radius of the nail are defined for the cone object data.
1372 The height of the cone is recomputed as 2 * heights of nail and divided by 9.
1374 @subsubsection occt_ocaf_8a_3_2 Computation
1376 The Function Mechanism is responsible for re-computation of the nail.
1377 It will be described in detail later in this document.
1379 A data leaf consists of the reference to the location of the real data
1380 and a real value defining a coefficient of multiplication of the referenced data.
1382 For example, the height of the long cylinder is defined as a reference to the height of the cone
1383 with coefficient 3. The data leaf of the height of the long cylinder
1384 should contain two attributes: a reference to the height of cone and a real value equal to 3.
1386 @subsubsection occt_ocaf_8a_3_3 Visualization
1388 The shape resulting of the nail function can be displayed using the standard OCAF visualization mechanism.
1390 @subsubsection occt_ocaf_8a_3_4 Removal of the nail
1392 To automatically erase the nail from the viewer and the data tree it is enough to clean the nail leaf from attributes.
1394 @subsection occt_ocaf_8a_4 Step 3: Functions
1396 The nail is defined by four functions: the cone, the two cylinders and the nail function.
1397 The function of the cone is independent. The functions of the cylinders depend on the cone function.
1398 The nail function depends on the results of all functions:
1400 @image html ocaf_functionmechanism_wp_image005.png "A graph of dependencies between functions"
1401 @image latex ocaf_functionmechanism_wp_image005.png "A graph of dependencies between functions"
1403 Computation of the model starts with the cone function, then the long cylinder,
1404 after that the header cylinder and, finally, the result is generated by the nail function at the end of function chain.
1406 The Function Mechanism of Open CASCADE Technology creates this graph of dependencies
1407 and allows iterating it following the dependencies.
1408 The only thing the Function Mechanism requires from its user
1409 is the implementation of pure virtual methods of *TFunction_Driver*:
1411 * <i>\::Arguments()</i> -- returns a list of arguments for the function
1412 * <i>\::Results()</i> -- returns a list of results of the function
1414 These methods give the Function Mechanism the information on the location of arguments
1415 and results of the function and allow building a graph of functions.
1416 The class *TFunction_Iterator* iterates the functions of the graph in the execution order.
1418 The pure virtual method *TFunction_Driver::Execute()* calculating the function should be overridden.
1420 The method <i>\::MustExecute()</i> calls the method <i>\::Arguments()</i> of the function driver
1421 and ideally this information (knowledge of modification of arguments of the function) is enough
1422 to make a decision whether the function should be executed or not. Therefore, this method usually shouldn’t be overridden.
1424 The cone and cylinder functions differ only in geometrical construction algorithms.
1425 Other parameters are the same (position, radius and height).
1427 It means that it is possible to create a base class -- function driver for the three functions,
1428 and two descendant classes producing: a cone or a cylinder.
1430 For the base function driver the methods <i>\::Arguments()</i> and <i>\::Results()</i> will be overridden.
1431 Two descendant function drivers responsible for creation of a cone and a cylinder will override only the method <i>\::Execute()</i>.
1433 The method <i>\::Arguments()</i> of the function driver of the nail returns the results of the functions located under it in the tree of leaves. The method <i>\::Execute()</i> just collects the results of the functions and makes one shape -- a nail.
1435 This way the data model using the Function Mechanism is ready for usage. Do not forget to introduce the function drivers for a function driver table with the help of *TFunction_DriverTable* class.
1437 @subsection occt_ocaf_8a_5 Example 1: iteration and execution of functions.
1439 This is an example of the code for iteration and execution of functions.
1441 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.cpp}
1443 // The scope of functions is defined.
1444 Handle(TFunction_Scope) scope = TFunction_Scope::Set( anyLabel );
1446 // The information on modifications in the model is received.
1447 TFunction_Logbook& log = scope-GetLogbook();
1449 // The iterator is iInitialized by the scope of functions.
1450 TFunction_Iterator iterator( anyLabel );
1451 Iterator.SetUsageOfExecutionOrder( true );
1453 // The function is iterated, its dependency is checked on the modified data and executed if necessary.
1454 for (; iterator.more(); iterator.Next())
1456 // The function iterator may return a list of current functions for execution.
1457 // It might be useful for multi-threaded execution of functions.
1458 const TDF_LabelList& currentFunctions = iterator.Current();
1460 //The list of current functions is iterated.
1461 TDF_ListIteratorOfLabelList currentterator( currentFucntions );
1462 for (; currentIterator.More(); currentIterator.Next())
1464 // An interface for the function is created.
1465 TFunction_IFunction interface( currentIterator.Value() );
1467 // The function driver is retrieved.
1468 Handle(TFunction_Driver) driver = interface.GetDriver();
1470 // The dependency of the function on the modified data is checked.
1471 If (driver-MustExecute( log ))
1473 // The function is executed.
1474 int ret = driver-Execute( log );
1477 } // end if check on modification
1478 } // end of iteration of current functions
1479 } // end of iteration of functions.
1481 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1483 @subsection occt_ocaf_8a_6 Example 2: Cylinder function driver
1485 This is an example of the code for a cylinder function driver. To make the things clearer, the methods <i>\::Arguments()</i> and <i>\::Results()</i> from the base class are also mentioned.
1487 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.cpp}
1489 // A virtual method ::Arguments() returns a list of arguments of the function.
1490 CylinderDriver::Arguments( TDF_LabelList& args )
1492 // The direct arguments, located at sub-leaves of the fucntion, are collected (see picture 2).
1493 TDF_ChildIterator cIterator( Label(), false );
1494 for (; cIterator.More(); cIterator.Next() )
1497 TDF_Label sublabel = cIterator.Value();
1498 Args.Append( sublabel );
1500 // The references to the external data are checked.
1501 Handle(TDF_Reference) ref;
1502 If ( sublabel.FindAttribute( TDF_Reference::GetID(), ref ) )
1504 args.Append( ref-Get() );
1508 // A virtual method ::Results() returns a list of result leaves.
1509 CylinderDriver::Results( TDF_LabelList& res )
1511 // The result is kept at the function label.
1512 Res.Append( Label() );
1515 // Execution of the function driver.
1516 Int CylinderDriver::Execute( TFunction_Logbook& log )
1518 // Position of the cylinder - position of the first function (cone)
1519 //is elevated along Z for height values of all previous functions.
1520 gp_Ax2 axes = …. // out of the scope of this guide.
1521 // The radius value is retrieved.
1522 // It is located at second child sub-leaf (see the picture 2).
1523 TDF_Label radiusLabel = Label().FindChild( 2 );
1525 // The multiplicator of the radius ()is retrieved.
1526 Handle(TDataStd_Real) radiusValue;
1527 radiusLabel.FindAttribute( TDataStd_Real::GetID(), radiusValue);
1529 // The reference to the radius is retrieved.
1530 Handle(TDF_Reference) refRadius;
1531 RadiusLabel.FindAttribute( TDF_Reference::GetID(), refRadius );
1533 // The radius value is calculated.
1534 double radius = 0.0;
1536 if ( refRadius.IsNull() )
1538 radius = radiusValue-Get();
1542 // The referenced radius value is retrieved.
1543 Handle(TDataStd_Real) referencedRadiusValue;
1544 RefRadius-Get().FindAttribute(TDataStd_Real::GetID() ,referencedRadiusValue );
1545 radius = referencedRadiusValue-Get() * radiusValue-Get();
1548 // The height value is retrieved.
1549 double height = … // similar code to taking the radius value.
1551 // The cylinder is created.
1552 TopoDS_Shape cylinder = BRepPrimAPI_MakeCylinder(axes, radius, height);
1554 // The result (cylinder) is set
1555 TNaming_Builder builder( Label() );
1556 Builder.Generated( cylinder );
1558 // The modification of the result leaf is saved in the log.
1559 log.SetImpacted( Label() );
1563 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1567 @section occt_ocaf_9 XML Support
1569 Writing and reading XML files in OCCT is provided by LDOM package, which constitutes an integral part
1570 of XML OCAF persistence, which is the optional component provided on top of Open CASCADE Technology.
1572 The Light DOM (LDOM) package contains classes maintaining a data structure whose main principles conform to W3C DOM Level 1 Recommendations. The purpose of these classes as required by XML OCAF persistence schema is to:
1573 * Maintain a tree structure of objects in memory representing the XML document. The root of the structure is an object of the *LDOM_Document* type. This object contains all the data corresponding to a given XML document and contains one object of the *LDOM_Element* type named "document element". The document element contains other *LDOM_Element* objects forming a tree. Other types of nodes: *LDOM_Attr, LDOM_Text, LDOM_Comment* and *LDOM_CDATASection* -- represent the corresponding XML types and serve as branches of the tree of elements.
1574 * Provide class *LDOM_Parser* to read XML files and convert them to *LDOM_Document* objects.
1575 * Provide class *LDOM_XmlWriter* to convert *LDOM_Document* to a character stream in XML format and store it in file.
1577 This package covers the functionality provided by numerous products known as "DOM parsers". Unlike most of them, LDOM was specifically developed to meet the following requirements:
1578 * To minimize the virtual memory allocated by DOM data structures. In average, the amount of memory of LDOM is the same as the XML file size (UTF-8).
1579 * To minimize the time required for parsing and formatting XML, as well as for access to DOM data structures.
1581 Both these requirements are important when XML files are processed by applications if these files are relatively large (occupying megabytes and even hundreds of megabytes). To meet the requirements, some limitations were imposed on the DOM Level 1 specification; these limitations are insignificant in applications like OCAF. Some of these limitations can be overridden in the course of future developments. The main limitations are:
1582 * No Unicode support as well as various other encodings; only ASCII strings are used in DOM/XML. Note: There is a data type *TCollection_ExtendedString* for wide character data. This type is supported by *LDOM_String* as a sequence of numbers.
1583 * Some superfluous methods are deleted: *getPreviousSibling, getParentNode,* etc.
1584 * No resolution of XML Entities of any kind
1585 * No support for DTD: the parser just checks for observance of general XML rules and never validates documents.
1586 * Only 5 available types of DOM nodes: *LDOM_Element, LDOM_Attr, LDOM_Text, LDOM_Comment* and *LDOM_CDATASection*.
1587 * No support of Namespaces; prefixed names are used instead of qualified names.
1588 * No support of the interface *DOMException* (no exception when attempting to remove a non-existing node).
1590 LDOM is dependent on Kernel OCCT classes only. Therefore, it can be used outside OCAF persistence in various algorithms where DOM/XML support may be required.
1592 @subsection occt_ocaf_9_1 Document Drivers
1594 The drivers for document storage and retrieval manage conversion between a transient OCAF
1595 Document in memory and its persistent reflection in a container (disk, memory, network). For XML Persistence, they are defined in the package XmlDrivers.
1597 The main methods (entry points) of these drivers are:
1598 * *Write()* -- for a storage driver;
1599 * *Read()* -- for a retrieval driver.
1601 The most common case (which is implemented in XML Persistence) is writing/reading document to/from a regular OS file. Such conversion is performed in two steps:
1603 First it is necessary to convert the transient document into another form (called persistent), suitable for writing into a file, and vice versa.
1604 In XML Persistence LDOM_Document is used as the persistent form of an OCAF Document and the DOM_Nodes are the persistent objects.
1605 An OCAF Document is a tree of labels with attributes. Its transformation into a persistent form can be functionally divided into two parts:
1606 * Conversion of the labels structure, which is performed by the method XmlMDF::FromTo()
1607 * Conversion of the attributes and their underlying objects, which is performed by the corresponding attribute drivers (one driver per attribute type).
1609 The driver for each attribute is selected from a table of drivers, either by attribute
1610 type (on storage) or by the name of the corresponding DOM_Element (on retrieval).
1611 The table of drivers is created by by methods *XmlDrivers_DocumentStorageDriver::AttributeDrivers()*
1612 and *XmlDrivers_DocumentRetrievalDriver::AttributeDrivers()*.
1614 Then the persistent document is written into a file (or read from a file).
1615 In standard persistence Storage and FSD packages contain classes for writing/reading the persistent document into a file. In XML persistence *LDOMParser* and *LDOM_XmlWriter* are used instead.
1617 Usually, the library containing document storage and retrieval drivers is loaded at run time by a plugin mechanism. To support this in XML Persistence, there is a plugin *XmlPlugin* and a *Factory()* method in the *XmlDrivers* package. This method compares passed GUIDs with known GUIDs and returns the corresponding driver or generates an exception if the GUID is unknown.
1619 The application defines which GUID is needed for document storage or retrieval and in which library it should be found. This depends on document format and application resources. Resources for XML Persistence and also for standard persistence are found in the StdResource unit. They are written for the XmlOcaf document format.
1621 @subsection occt_ocaf_9_2 Attribute Drivers
1623 There is one attribute driver for XML persistence for each transient attribute from a set of standard OCAF attributes, with the exception of attribute types, which are never stored (pure transient). Standard OCAF attributes are collected in six packages, and their drivers also follow this distribution. Driver for attribute <i>T*_*</i> is called <i>XmlM*_*</i>. Conversion between transient and persistent form of attribute is performed by two methods *Paste()* of attribute driver.
1625 *XmlMDF_ADriver* is the root class for all attribute drivers.
1627 At the beginning of storage/retrieval process, one instance of each attribute driver is created and appended to driver table implemented as *XmlMDF_ADriverTable*. During OCAF Data storage, attribute drivers are retrieved from the driver table by the type of attribute. In the retrieval step, a data map is created linking names of *DOM_Elements* and attribute drivers, and then attribute drivers are sought in this map by *DOM_Element* qualified tag names.
1629 Every transient attribute is saved as a *DOM_Element* (root element of OCAF attribute) with attributes and possibly sub-nodes. The name of the root element can be defined in the attribute driver as a string passed to the base class constructor. The default is the attribute type name. Similarly, namespace prefixes for each attribute can be set. There is no default value, but it is possible to pass NULL or an empty string to store attributes without namespace prefixes.
1631 The basic class *XmlMDF_ADriver* supports errors reporting via the method *WriteMessage(const TCollection_ExtendedString&)*. It sends a message string to its message driver which is initialized in the constructor with a *Handle(CDM_MessageDriver)* passed from the application by Document Storage/Retrieval Driver.
1633 @subsection occt_ocaf_9_3 XML Document Structure
1635 Every XML Document has one root element, which may have attributes and contain other nodes. In OCAF XML Documents the root element is named "document" and has attribute "format" with the name of the OCAF Schema used to generate the file. The standard XML format is "XmlOcaf". The following elements are sub-elements of \<document\> and should be unique entries as its sub-elements, in a specific order. The order is:
1636 * **Element info** -- contains strings identifying the format version and other parameters of the OCAF XML document. Normally, data under the element is used by persistence algorithms to correctly retrieve and initialize an OCAF document. The data also includes a copyright string.
1637 * **Element comments** -- consists of an unlimited number of \<comment\> sub-elements containing necessary comment strings.
1638 * **Element label** -- the root label of the document data structure, with the XML attribute "tag" equal to 0. It contains all the OCAF data (labels, attributes) as tree of XML elements. Every sub-label is identified by a tag (positive integer) defining a unique key for all sub-labels of a label. Every label can contain any number of elements representing OCAF attributes (see OCAF Attributes Representation below).
1639 * **Element shapes** -- contains geometrical and topological entities in BRep format. These entities being referenced by OCAF attributes written under the element \<label\>. This element is empty if there are no shapes in the document. It is only output if attribute driver *XmlMNaming_NamedShapeDriver* has been added to drivers table by the *DocumentStorageDriver*.
1641 ### OCAF Attributes Representation
1643 In XML documents, OCAF attributes are elements whose name identifies the OCAF attribute type. These elements may have a simple (string or number) or complex (sub-elements) structure, depending on the architecture of OCAF attribute. Every XML type for OCAF attribute possesses a unique positive integer "id" XML attribute identifying the OCAF attribute throughout the document. To ensure "id" uniqueness, the attribute name "id" is reserved and is only used to indicate and identify elements which may be referenced from other parts of the OCAF XML document.
1644 For every standard OCAF attribute, its XML name matches the name of a C++ class in Transient data model. Generally, the XML name of OCAF attribute can be specified in the corresponding attribute driver.
1645 XML types for OCAF attributes are declared with XML W3C Schema in a few XSD files where OCAF attributes are grouped by the package where they are defined.
1647 ### Example of resulting XML file
1649 The following example is a sample text from an XML file obtained by storing an OCAF document with two labels (0: and 0:2) and two attributes -- *TDataStd_Name* (on label 0:) and *TNaming_NamedShape* (on label 0:2). The \<shapes\> section contents are replaced by an ellipsis.
1652 <?xml version="1.0" encoding="UTF-8"?>
1653 <document format="XmlOcaf" xmlns="http://www.opencascade.org/OCAF/XML" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
1654 xsi:schemaLocation="http://www.opencascade.org/OCAF/XML http://www.opencascade.org/OCAF/XML/XmlOcaf.xsd">
1656 <info date="2001-10-04" schemav="0" objnb="3">
1657 <iitem>Copyright: Open Cascade, 2001</iitem>
1658 <iitem>STORAGE_VERSION: PCDM_ReadWriter_1</iitem>
1659 <iitem>REFERENCE_COUNTER: 0</iitem>
1660 <iitem>MODIFICATION_COUNTER: 1</iitem>
1664 <TDataStd_Name id="1">Document_1</TDataStd_Name>
1666 <TNaming_NamedShape id="2" evolution="primitive">
1669 <shape tshape="+34" index="1"/>
1671 </TNaming_NamedShape>
1681 @subsection occt_ocaf_9_4 XML Schema
1683 The XML Schema defines the class of a document.
1685 The full structure of OCAF XML documents is described as a set of XML W3C Schema files with definitions of all XML element types. The definitions provided cannot be overridden. If any application defines new persistence schemas, it can use all the definitions from the present XSD files but if it creates new or redefines existing types, the definition must be done under other namespace(s).
1687 There are other ways to declare XML data, different from W3C Schema, and it should be possible to use them to the extent of their capabilities of expressing the particular structure and constraints of our XML data model. However, it must be noted that the W3C Schema is the primary format for declarations and as such, it is the format supported for future improvements of Open CASCADE Technology, including the development of specific applications using OCAF XML persistence.
1689 The Schema files (XSD) are intended for two purposes:
1690 * documenting the data format of files generated by OCAF;
1691 * validation of documents when they are used by external (non-OCAF) applications, e.g., to generate reports.
1693 The Schema definitions are not used by OCAF XML Persistence algorithms when saving and restoring XML documents. There are internal checks to ensure validity when processing every type of data.
1695 ### Management of Namespaces
1697 Both the XML format and the XML OCAF persistence code are extensible in the sense that every new development can reuse everything that has been created in previous projects. For the XML format, this extensibility is supported by assigning names of XML objects (elements) to different XML Namespaces. Hence, XML elements defined in different projects (in different persistence libraries) can easily be combined into the same XML documents. An example is the XCAF XML persistence built as an extension to the Standard OCAF XML persistence <i>[File XmlXcaf.xsd]</i>. For the correct management of Namespaces it is necessary to:
1698 * Define *targetNamespace* in the new XSD file describing the format.
1699 * Declare (in *XSD* files) all elements and types in the targetNamespace to appear without a namespace prefix; all other elements and types use the appropriate prefix (such as "ocaf:").
1700 * Add (in the new *DocumentStorageDriver*) the *targetNamespace* accompanied with its prefix, using method *XmlDrivers_DocumentStorageDriver::AddNamespace*. The same is done for all namespaces objects which are used by the new persistence, with the exception of the "ocaf" namespace.
1701 * Pass (in every OCAF attribute driver) the namespace prefix of the *targetNamespace* to the constructor of *XmlMDF_ADriver*.
1703 @section occt_ocaf_9a Persistent Data Storage
1705 @subsection occt_ocaf_9a_1 Introduction
1707 In OCAF, persistence, that is, the mechanism used to save a document in a file, is based on an explicit formal description of the data saved.
1709 When you open a document, the application reads the corresponding file and first creates a memory representation of it. This representation is then converted to the application data model — the OCAF-based data structure the application operates on. The file's memory representation consists of objects defined by classes known as persistent.
1711 OCAF includes a ready-to-use schema suitable for most applications.
1712 However, it can be extended if needed.
1714 Applications using compound documents extensively (saving data in many files linked together) should implement data management services. It is out the scope of OCAF to provide functions such as:
1715 * Version and configuration management of compound documents;
1716 * Querying a referenced document for its referencing documents.
1718 In order to ease the delegation of document management to a data management application, OCAF encapsulates the file management functions in a driver (the meta-data driver). You have to implement this driver for your application to communicate with the data management system of your choice.
1721 @subsection occt_ocaf_9a_2 Schemes of Persistence
1723 There are three schemes of persistence, which you can use to store and retrieve OCAF data (documents):
1725 * <i> Standard</i> persistence schema, compatible with previous OCAF applications. This schema is deprecated and supports only reading of standard attributes (no writing).
1726 * <i> XmlOcaf</i> persistence, allowing the storage of all OCAF data in XML form
1727 * <i> BinOcaf</i> persistence, allowing the storage of all OCAF data in binary format form
1730 In an OCAF application you can use any persistence schema or
1731 even all three of them. The choice is made depending on the *Format* string of stored OCAF documents
1732 or automatically by the file header data -- on retrieval.
1734 @section occt_ocaf_10 GLOSSARY
1736 * **Application** -- a document container holding all documents containing all application data.
1737 * **Application data** -- the data produced by an application, as opposed to data referring to it.
1738 * **Associativity of data** -- the ability to propagate modifications made to one document to other documents, which refer to such document. Modification propagation is:
1739 * unidirectional, that is, from the referenced to the referencing document(s), or
1740 * bi-directional, from the referencing to the referenced document and vice-versa.
1741 * **Attribute** -- a container for application data. An attribute is attached to a label in the hierarchy of the data framework.
1742 * **Child** -- a label created from another label, which by definition, is the father label.
1743 * **Compound document** -- a set of interdependent documents, linked to each other by means of external references. These references provide the associativity of data.
1744 * **Data framework** -- a tree-like data structure which in OCAF, is a tree of labels with data attached to them in the form of attributes. This tree of labels is accessible through the services of the *TDocStd_Document* class.
1745 * **Document** -- a container for a data framework which grants access to the data, and is, in its turn, contained by an application. A document also allows you to:
1746 * Manage modifications, providing Undo and Redo functions
1747 * Manage command transactions
1748 * Update external links
1749 * Manage save and restore options
1750 * Store the names of software extensions.
1751 * **Driver** -- an abstract class, which defines the communications protocol with a system.
1752 * **Entry** -- an ASCII character string containing the tag list of a label. For example:
1753 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.cpp}
1755 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1757 * **External links** -- references from one data structure to another data structure in another document.
1758 To store these references properly, a label must also contain an external link attribute.
1759 * **Father** -- a label, from which other labels have been created. The other labels are, by definition, the children of this label.
1760 * **Framework** -- a group of co-operating classes which enable a design to be re-used for a given category of problem. The framework guides the architecture of the application by breaking it up into abstract classes, each of which has different responsibilities and collaborates in a predefined way. Application developer creates a specialized framework by:
1761 * defining new classes which inherit from these abstract classes
1762 * composing framework class instances
1763 * implementing the services required by the framework.
1765 In C++, the application behavior is implemented in virtual functions redefined in these derived classes. This is known as overriding.
1767 * **GUID** -- Global Universal ID. A string of 37 characters intended to uniquely identify an object. For example:
1768 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.cpp}
1769 2a96b602-ec8b-11d0-bee7-080009dc3333
1770 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1772 * **Label** -- a point in the data framework, which allows data to be attached to it by means of attributes. It has a name in the form of an entry, which identifies its place in the data framework.
1773 * **Modified label** -- containing attributes whose data has been modified.
1774 * **Reference key** -- an invariant reference, which may refer to any type of data used in an application. In its transient form, it is a label in the data framework, and the data is attached to it in the form of attributes. In its persistent form, it is an entry of the label. It allows an application to recover any entity in the current session or in a previous session.
1775 * **Resource file** -- a file containing a list of each document’s schema name and the storage and retrieval plug-ins for that document.
1776 * **Root** -- the starting point of the data framework. This point is the top label in the framework. It is represented by the [0] entry and is created at the same time with the document you are working on.
1777 * **Scope** -- the set of all the attributes and labels which depend on a given label.
1778 * **Tag list** -- a list of integers, which identify the place of a label in the data framework. This list is displayed in an entry.
1779 * **Topological naming** -- systematic referencing of topological entities so that these entities can still be identified after the models they belong to have gone through several steps in modeling. In other words, topological naming allows you to track entities through the steps in the modeling process. This referencing is needed when a model is edited and regenerated, and can be seen as a mapping of labels and name attributes of the entities in the old version of a model to those of the corresponding entities in its new version. Note that if the topology of a model changes during the modeling, this mapping may not fully coincide. A Boolean operation, for example, may split edges.
1780 * **Topological tracking** -- following a topological entity in a model through the steps taken to edit and regenerate that model.
1781 * **Valid label** -- in a data framework, this is a label, which is already recomputed in the scope of regeneration sequence and includes the label containing a feature which is to be recalculated. Consider the case of a box to which you first add a fillet, then a protrusion feature. For recalculation purposes, only valid labels of each construction stage are used. In recalculating a fillet, they are only those of the box and the fillet, not the protrusion feature which was added afterwards.
1783 @section occt_ocaf_11 Samples
1785 @subsection occt_ocaf_11_a Getting Started
1787 At the beginning of your development, you first define an application class by inheriting from the Application abstract class.
1788 You only have to create and determine the resources of the application
1789 for specifying the format of your documents (you generally use the standard one) and their file extension.
1791 Then, you design the application data model by organizing attributes you choose among those provided with OCAF.
1792 You can specialize these attributes using the User attribute. For example, if you need a reflection coefficient,
1793 you aggregate a User attribute identified as a reflection coefficient
1794 with a Real attribute containing the value of the coefficient (as such, you don't define a new class).
1796 If you need application specific data not provided with OCAF, for example,
1797 to incorporate a finite element model in the data structure,
1798 you define a new attribute class containing the mesh,
1799 and you include its persistent homologue in a new file format.
1801 Once you have implemented the commands which create and modify the data structure
1802 according to your specification, OCAF provides you, without any additional programming:
1804 * Persistent reference to any data, including geometric elements — several documents can be linked with such reference;
1805 * Document-View association;
1806 * Ready-to-use functions such as :
1808 * Save and open application data.
1810 Finally, you develop the application's graphical user interface using the toolkit of your choice, for example:
1811 * KDE Qt or GNOME GTK+ on Linux;
1812 * Microsoft Foundation Classes (MFC) on Windows Motif on Sun;
1813 * Other commercial products such as Ilog Views.
1815 You can also implement the user interface in the Java language using
1816 the Swing-based Java Application Desktop component (JAD) provided with OCAF.
1818 @subsection occt_ocaf_11_b An example of OCAF usage
1820 To create a useful OCAF-based application, it is necessary to redefine two deferred methods: <i> Formats</i> and <i> ResourcesName</i>
1822 In the <i> Formats </i> method, add the format of the documents, which need to be read by the application and may have been built in other applications.
1827 void myApplication::Formats(TColStd_SequenceOfExtendedString& Formats)
1829 Formats.Append(TCollection_ExtendedString ("OCAF-myApplication"));
1833 In the <i> ResourcesName</i> method, you only define the name of the resource file. This
1834 file contains several definitions for the saving and opening mechanisms associated
1835 with each format and calling of the plug-in file.
1838 Standard_CString myApplication::ResourcesName()
1840 return Standard_CString ("Resources");
1844 To obtain the saving and opening mechanisms, it is necessary to set two environment variables: <i> CSF_PluginDefaults</i>, which defines the path of the plug-in file, and <i> CSF_ResourcesDefault</i>, which defines the resource file:
1847 SetEnvironmentVariable ( "CSF_ResourcesDefaults",myDirectory);
1848 SetEnvironmentVariable ( "CSF_PluginDefaults",myDirectory);
1851 The plugin and the resource files of the application will be located in <i> myDirector</i>.
1852 The name of the plugin file must be <i>Plugin</i>.
1856 The resource file describes the documents (type and extension) and
1857 the type of data that the application can manipulate
1858 by identifying the storage and retrieval drivers appropriate for this data.
1860 Each driver is unique and identified by a GUID generated, for example, with the <i> uuidgen </i> tool in Windows.
1862 Five drivers are required to use all standard attributes provided within OCAF:
1864 * the schema driver (ad696002-5b34-11d1-b5ba-00a0c9064368)
1865 * the document storage driver (ad696000-5b34-11d1-b5ba-00a0c9064368)
1866 * the document retrieval driver (ad696001-5b34-11d1-b5ba-00a0c9064368)
1867 * the attribute storage driver (47b0b826-d931-11d1-b5da-00a0c9064368)
1868 * the attribute retrieval driver (47b0b827-d931-11d1-b5da-00a0c9064368)
1870 These drivers are provided as plug-ins and are located in the <i> PappStdPlugin</i> library.
1873 For example, this is a resource file, which declares a new model document OCAF-MyApplication:
1876 formatlist:OCAF-MyApplication
1877 OCAF-MyApplication.Description: MyApplication Document Version 1.0
1878 OCAF-MyApplication.FileExtension: sta
1879 OCAF-MyApplication.StoragePlugin: ad696000-5b34-11d1-b5ba-00a0c9064368
1880 OCAF-MyApplication.RetrievalPlugin: ad696001-5b34-11d1-b5ba-00a0c9064368
1881 OCAF-MyApplicationSchema: ad696002-5b34-11d1-b5ba-00a0c9064368
1882 OCAF-MyApplication.AttributeStoragePlugin: 47b0b826-d931-11d1-b5da-00a0c9064368
1883 OCAF-MyApplication.AttributeRetrievalPlugin: 47b0b827-d931-11d1-b5da-00a0c9064368
1889 The plugin file describes the list of required plug-ins to run the application and the
1890 libraries in which plug-ins are located.
1892 You need at least the <i> FWOSPlugin</i> and the plug-in drivers to run an OCAF application.
1894 The syntax of each item is <i> Identification.Location Library_Name, </i> where:
1895 * Identification is GUID.
1896 * Location defines the location of the Identification (where its definition is found).
1897 * Library_Name is the name (and path to) the library, where the plug-in is located.
1899 For example, this is a Plugin file:
1902 a148e300-5740-11d1-a904-080036aaa103.Location: FWOSPlugin
1903 ! base document drivers plugin
1904 ad696000-5b34-11d1-b5ba-00a0c9064368.Location: PAppStdPlugin
1905 ad696001-5b34-11d1-b5ba-00a0c9064368.Location: PAppStdPlugin
1906 ad696002-5b34-11d1-b5ba-00a0c9064368.Location: PAppStdPlugin
1907 47b0b826-d931-11d1-b5da-00a0c9064368.Location: PAppStdPlugin
1908 47b0b827-d931-11d1-b5da-00a0c9064368.Location: PAppStdPlugin
1913 @subsection occt_ocaf_11_1 Implementation of Attribute Transformation in a HXX file
1915 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.cpp}
1916 \#include <TDF_Attribute.hxx>
1918 \#include <gp_Ax3.hxx>
1919 \#include <gp_Pnt.hxx>
1920 \#include <gp_Vec.hxx>
1921 \#include <gp_Trsf.hxx>
1923 //! This attribute implements a transformation data container
1924 class MyPackage_Transformation : public TDF_Attribute
1927 //!@name Static methods
1929 //! The method returns a unique GUID of this attribute.
1930 //! By means of this GUID this attribute may be identified
1931 //! among other attributes attached to the same label.
1932 Standard_EXPORT static const Standard_GUID& GetID ();
1934 //! Finds or creates the attribute attached to <theLabel>.
1935 //! The found or created attribute is returned.
1936 Standard_EXPORT static Handle(MyPackage_Transformation) Set (const TDF_Label theLabel);
1938 //!@name Methods for access to the attribute data
1940 //! The method returns the transformation.
1941 Standard_EXPORT gp_Trsf Get () const;
1943 //!@name Methods for setting the data of transformation
1945 //! The method defines a rotation type of transformation.
1946 Standard_EXPORT void SetRotation (const gp_Ax1& theAxis, Standard_Real theAngle);
1948 //! The method defines a translation type of transformation.
1949 Standard_EXPORT void SetTranslation (const gp_Vec& theVector);
1951 //! The method defines a point mirror type of transformation (point symmetry).
1952 Standard_EXPORT void SetMirror (const gp_Pnt& thePoint);
1954 //! The method defines an axis mirror type of transformation (axial symmetry).
1955 Standard_EXPORT void SetMirror (const gp_Ax1& theAxis);
1957 //! The method defines a point mirror type of transformation (planar symmetry).
1958 Standard_EXPORT void SetMirror (const gp_Ax2& thePlane);
1960 //! The method defines a scale type of transformation.
1961 Standard_EXPORT void SetScale (const gp_Pnt& thePoint, Standard_Real theScale);
1963 //! The method defines a complex type of transformation from one co-ordinate system to another.
1964 Standard_EXPORT void SetTransformation (const gp_Ax3& theCoordinateSystem1, const gp_Ax3& theCoordinateSystem2);
1966 //!@name Overridden methods from TDF_Attribute
1968 //! The method returns a unique GUID of the attribute.
1969 //! By means of this GUID this attribute may be identified among other attributes attached to the same label.
1970 Standard_EXPORT const Standard_GUID& ID () const;
1972 //! The method is called on Undo / Redo.
1973 //! It copies the content of theAttribute into this attribute (copies the fields).
1974 Standard_EXPORT void Restore (const Handle(TDF_Attribute)& theAttribute);
1976 //! It creates a new instance of this attribute.
1977 //! It is called on Copy / Paste, Undo / Redo.
1978 Standard_EXPORT Handle(TDF_Attribute) NewEmpty () const;
1980 //! The method is called on Copy / Paste.
1981 //! It copies the content of this attribute into theAttribute (copies the fields).
1982 Standard_EXPORT void Paste (const Handle(TDF_Attribute)& theAttribute, const Handle(TDF_RelocationTable)& theRelocationTable);
1984 //! Prints the content of this attribute into the stream.
1985 Standard_EXPORT Standard_OStream& Dump(Standard_OStream& theOS);
1987 //!@name Constructor
1989 //! The C++ constructor of this atribute class.
1990 //! Usually it is never called outside this class.
1991 Standard_EXPORT MyPackage_Transformation();
1996 // Axes (Ax1, Ax2, Ax3)
2003 Standard_Real myAngle;
2004 Standard_Real myScale;
2007 gp_Pnt myFirstPoint;
2008 gp_Pnt mySecondPoint;
2010 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
2012 @subsection occt_ocaf_11_2 Implementation of Attribute Transformation in a CPP file
2014 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~{.cpp}
2015 \#include <MyPackage_Transformation.hxx>
2017 //=======================================================================
2019 //purpose : The method returns a unique GUID of this attribute.
2020 // By means of this GUID this attribute may be identified
2021 // among other attributes attached to the same label.
2022 //=======================================================================
2023 const Standard_GUID& MyPackage_Transformation::GetID()
2025 static Standard_GUID ID("4443368E-C808-4468-984D-B26906BA8573");
2029 //=======================================================================
2031 //purpose : Finds or creates the attribute attached to <theLabel>.
2032 // The found or created attribute is returned.
2033 //=======================================================================
2034 Handle(MyPackage_Transformation) MyPackage_Transformation::Set(const TDF_Label& theLabel)
2036 Handle(MyPackage_Transformation) T;
2037 if (!theLabel.FindAttribute(MyPackage_Transformation::GetID(), T))
2039 T = new MyPackage_Transformation();
2040 theLabel.AddAttribute(T);
2045 //=======================================================================
2047 //purpose : The method returns the transformation.
2048 //=======================================================================
2049 gp_Trsf MyPackage_Transformation::Get() const
2051 gp_Trsf transformation;
2060 transformation.SetRotation(myAx1, myAngle);
2063 case gp_Translation:
2065 transformation.SetTranslation(myFirstPoint, mySecondPoint);
2070 transformation.SetMirror(myFirstPoint);
2075 transformation.SetMirror(myAx1);
2080 transformation.SetMirror(myAx2);
2085 transformation.SetScale(myFirstPoint, myScale);
2088 case gp_CompoundTrsf:
2090 transformation.SetTransformation(myFirstAx3, mySecondAx3);
2098 return transformation;
2101 //=======================================================================
2102 //function : SetRotation
2103 //purpose : The method defines a rotation type of transformation.
2104 //=======================================================================
2105 void MyPackage_Transformation::SetRotation(const gp_Ax1& theAxis, const Standard_Real theAngle)
2108 myType = gp_Rotation;
2113 //=======================================================================
2114 //function : SetTranslation
2115 //purpose : The method defines a translation type of transformation.
2116 //=======================================================================
2117 void MyPackage_Transformation::SetTranslation(const gp_Vec& theVector)
2120 myType = gp_Translation;
2121 myFirstPoint.SetCoord(0, 0, 0);
2122 mySecondPoint.SetCoord(theVector.X(), theVector.Y(), theVector.Z());
2125 //=======================================================================
2126 //function : SetMirror
2127 //purpose : The method defines a point mirror type of transformation
2128 // (point symmetry).
2129 //=======================================================================
2130 void MyPackage_Transformation::SetMirror(const gp_Pnt& thePoint)
2133 myType = gp_PntMirror;
2134 myFirstPoint = thePoint;
2137 //=======================================================================
2138 //function : SetMirror
2139 //purpose : The method defines an axis mirror type of transformation
2140 // (axial symmetry).
2141 //=======================================================================
2142 void MyPackage_Transformation::SetMirror(const gp_Ax1& theAxis)
2145 myType = gp_Ax1Mirror;
2149 //=======================================================================
2150 //function : SetMirror
2151 //purpose : The method defines a point mirror type of transformation
2152 // (planar symmetry).
2153 //=======================================================================
2154 void MyPackage_Transformation::SetMirror(const gp_Ax2& thePlane)
2157 myType = gp_Ax2Mirror;
2161 //=======================================================================
2162 //function : SetScale
2163 //purpose : The method defines a scale type of transformation.
2164 //=======================================================================
2165 void MyPackage_Transformation::SetScale(const gp_Pnt& thePoint, const Standard_Real theScale)
2169 myFirstPoint = thePoint;
2173 //=======================================================================
2174 //function : SetTransformation
2175 //purpose : The method defines a complex type of transformation
2176 // from one co-ordinate system to another.
2177 //=======================================================================
2178 void MyPackage_Transformation::SetTransformation(const gp_Ax3& theCoordinateSystem1,
2179 const gp_Ax3& theCoordinateSystem2)
2182 myFirstAx3 = theCoordinateSystem1;
2183 mySecondAx3 = theCoordinateSystem2;
2186 //=======================================================================
2188 //purpose : The method returns a unique GUID of the attribute.
2189 // By means of this GUID this attribute may be identified
2190 // among other attributes attached to the same label.
2191 //=======================================================================
2192 const Standard_GUID& MyPackage_Transformation::ID() const
2197 //=======================================================================
2198 //function : Restore
2199 //purpose : The method is called on Undo / Redo.
2200 // It copies the content of <theAttribute>
2201 // into this attribute (copies the fields).
2202 //=======================================================================
2203 void MyPackage_Transformation::Restore(const Handle(TDF_Attribute)& theAttribute)
2205 Handle(MyPackage_Transformation) theTransformation = Handle(MyPackage_Transformation)::DownCast(theAttribute);
2206 myType = theTransformation->myType;
2207 myAx1 = theTransformation->myAx1;
2208 myAx2 = theTransformation->myAx2;
2209 myFirstAx3 = theTransformation->myFirstAx3;
2210 mySecondAx3 = theTransformation->mySecondAx3;
2211 myAngle = theTransformation->myAngle;
2212 myScale = theTransformation->myScale;
2213 myFirstPoint = theTransformation->myFirstPoint;
2214 mySecondPoint = theTransformation->mySecondPoint;
2217 //=======================================================================
2218 //function : NewEmpty
2219 //purpose : It creates a new instance of this attribute.
2220 // It is called on Copy / Paste, Undo / Redo.
2221 //=======================================================================
2222 Handle(TDF_Attribute) MyPackage_Transformation::NewEmpty() const
2224 return new MyPackage_Transformation();
2227 //=======================================================================
2229 //purpose : The method is called on Copy / Paste.
2230 // It copies the content of this attribute into
2231 // <theAttribute> (copies the fields).
2232 //=======================================================================
2233 void MyPackage_Transformation::Paste(const Handle(TDF_Attribute)& theAttribute,
2234 const Handle(TDF_RelocationTable)& ) const
2236 Handle(MyPackage_Transformation) theTransformation = Handle(MyPackage_Transformation)::DownCast(theAttribute);
2237 theTransformation->myType = myType;
2238 theTransformation->myAx1 = myAx1;
2239 theTransformation->myAx2 = myAx2;
2240 theTransformation->myFirstAx3 = myFirstAx3;
2241 theTransformation->mySecondAx3 = mySecondAx3;
2242 theTransformation->myAngle = myAngle;
2243 theTransformation->myScale = myScale;
2244 theTransformation->myFirstPoint = myFirstPoint;
2245 theTransformation->mySecondPoint = mySecondPoint;
2248 //=======================================================================
2250 //purpose : Prints the content of this attribute into the stream.
2251 //=======================================================================
2252 Standard_OStream& MyPackage_Transformation::Dump(Standard_OStream& anOS) const
2254 anOS = "Transformation: ";
2259 anOS = "gp_Identity";
2264 anOS = "gp_Rotation";
2267 case gp_Translation:
2269 anOS = "gp_Translation";
2274 anOS = "gp_PntMirror";
2279 anOS = "gp_Ax1Mirror";
2284 anOS = "gp_Ax2Mirror";
2292 case gp_CompoundTrsf:
2294 anOS = "gp_CompoundTrsf";
2306 //=======================================================================
2307 //function : MyPackage_Transformation
2308 //purpose : A constructor.
2309 //=======================================================================
2310 MyPackage_Transformation::MyPackage_Transformation():myType(gp_Identity){
2313 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
2315 @subsection occt_ocaf_11_3 Implementation of typical actions with standard OCAF attributes.
2317 There are four sample files provided in the directory 'OpenCasCade/ros/samples/ocafsamples'. They present typical actions with OCAF services (mainly for newcomers).
2318 The method *Sample()* of each file is not dedicated for execution 'as is', it is rather a set of logical actions using some OCAF services.
2320 ### TDataStd_Sample.cxx
2321 This sample contains templates for typical actions with the following standard OCAF attributes:
2322 - Starting with data framework;
2323 - TDataStd_Integer attribute management;
2324 - TDataStd_RealArray attribute management;
2325 - TDataStd_Comment attribute management;
2326 - TDataStd_Name attribute management;
2327 - TDataStd_UAttribute attribute management;
2328 - TDF_Reference attribute management;
2329 - TDataXtd_Point attribute management;
2330 - TDataXtd_Plane attribute management;
2331 - TDataXtd_Axis attribute management;
2332 - TDataXtd_Geometry attribute management;
2333 - TDataXtd_Constraint attribute management;
2334 - TDataStd_Directory attribute management;
2335 - TDataStd_TreeNode attribute management.
2337 ### TDocStd_Sample.cxx
2338 This sample contains template for the following typical actions:
2339 - creating application;
2340 - creating the new document (document contains a framework);
2341 - retrieving the document from a label of its framework;
2342 - filling a document with data;
2343 - saving a document in the file;
2344 - closing a document;
2345 - opening the document stored in the file;
2346 - copying content of a document to another document with possibility to update the copy in the future.
2348 ### TPrsStd_Sample.cxx
2349 This sample contains template for the following typical actions:
2350 - starting with data framework;
2351 - setting the TPrsStd_AISViewer in the framework;
2352 - initialization of aViewer;
2353 - finding TPrsStd_AISViewer attribute in the DataFramework;
2354 - getting AIS_InteractiveContext from TPrsStd_AISViewer;
2355 - adding driver to the map of drivers;
2356 - getting driver from the map of drivers;
2357 - setting TNaming_NamedShape to \<ShapeLabel\>;
2358 - setting the new TPrsStd_AISPresentation to \<ShapeLabel\>;
2361 - updating and displaying presentation of the attribute to be displayed;
2362 - setting a color to the displayed attribute;
2363 - getting transparency of the displayed attribute;
2365 - updating presentation of the attribute in viewer.
2367 ### TNaming_Sample.cxx
2368 This sample contains template for typical actions with OCAF Topological Naming services.
2369 The following scenario is used:
2370 - data framework initialization;
2371 - creating Box1 and pushing it as PRIMITIVE in DF;
2372 - creating Box2 and pushing it as PRIMITIVE in DF;
2373 - moving Box2 (applying a transformation);
2374 - pushing the selected edges of the top face of Box1 in DF;
2375 - creating a Fillet (using the selected edges) and pushing the result as a modification of Box1;
2376 - creating a Cut (Box1, Box2) as a modification of Box1 and push it in DF;
2377 - recovering the result from DF.