OCAF is an application framework for rapidly developing CAD applications. It provides services for modeling data, visualization, and modeling algorithms. It uses an application-document-attribute model with standard attributes for shapes, geometry, and user-defined attributes. Functions trigger attribute changes and the framework updates dependent attributes through a reference-key mechanism and transactional updates.

1. OpenCascade: (7.1.0)
OCAF (OpenCascade Application Framework)
王聖川
2017/9/4

2. Introduction
• OCAF, OpenCascade Application Framework. For rapidly
developing (CAD) application.
• Services:
• Uses modules:
• Modeling Data: shape implementation.
• Visualization: viewer.
• Modeling Algorithms: modeling functions implementation.
Development tasks Comments With OCAF
Creation of geometry Algorithm Calling the modeling libraries By developer
Data organization Including specific attributes and modeling process Simplified
Saving data in a file Notion of document Provided
Document-view management Provided
Application infrastructure New, Open, Close, Save and Save As File menus Provided
Undo-Redo Robust, multi-level Provided
Application-specific dialog boxes By developer

3. OCAF Architecture
• Application-Document-Attribute model.

4. Application-Document-Attribute
• Application: 管理documents.
• Documents: notifies data changes, updates external links,
saves/restores data, command transactions (undo/redo).
• Attributes: describes data. 描述資料屬性.
• Standard attributes: integer, real, string, …, tag, reference, tree
node.
• Shape attributes: shape, shape evolution.
• Geometric attributes: datums, constraints.
• User attributes: user-defined.
• Vis. Attributes: graphical data representation, 顯示資訊屬性.
• Function services: notification of data changes. 實作資料變更的事件
通知與傳遞機制.

5. Reference-Key
• 各種資料屬性, 透過reference-key機制做對應綁定(指定).
• 如下圖, face (topology) 幾何屬性, 與user texture, 貼圖屬性
都對應描述相同的referenc對象.
• face幾何資料重新計算時, user texture不用重新指定, 因為reference對
象不變.

6. Data Framework
• Tree structure實現reference-key model.
• Tag: Label的ID(整數), 可用在標示label的結構路徑位址.
• Label: Tree node. 屬性資料的reference來源節點. Label建立後不能被
刪除!?
• Attribute: 描述資料內容用的屬性物件. 儲存(綁定)在label中. 每種
attribute有自己獨特的GUID, 一個label可以加入多個attributes, 但相同
GUID的attribute不能重複.

7. User Defined Attribute
• Create new attribute class.
• 繼承TDF_Attribute class.
• 實作virtual methods: ID(), Restore(), Paste(), NewEmpty(), Dump().
• Read/write in XML or binary format: 參考官方說明. 實作plugin
packages (建立Xml*_*Driver class繼承XmlMDF_ADriver class ;
Bin*_*Driver class繼承BinMDF_ADriver class).
• Defined by UAttribute: 引用標準屬性, 組合出新屬性的資料
結構.
• 建立擁有獨特GUID之TDataStd_UAttribute物件.
• 針對新屬性設計的資料結構, 設計對應的child labels.

8. Compoud Document
• Xlink attribute.
• 描述外部文件連結資訊.
• Coffee machine文件中, 透過XLink引
用coffee pot文件資訊.

9. Document Transaction
• 軟體功能操作辦理機制.
• 每項操作辦理前, 會針對attributes做備份.
• 辦理確認有效後, 修改attributes, 備份銷毀.
• 操作辦理被中止或放棄時, 由備份還原attributes資料.
• 實現失敗還原 (功能操作遇到錯誤情況), 終止 (abort/cancel),
復原 (redo/undo)等軟體功能機制的開發.

10. Standard Document Service
• 一份document管理一份data framework.
• Application (TDocStd_Application class).
• 管理documents.
• Document (TDocStd_Document class).
• 管理labels (data framework).
• Storage format: DefineFormat() API定義軟體的檔案格式內容 (retrival
drivers, storage drivers). 也可透過resource file定義.
• Cut, copy, paste.
• External Links.

11. Standard Storage Formats
• Standard formats.
Format Persistent toolkit OCAF attributes covered
Legacy formats (read only)
OCC-StdLite TKStdL TKLCAF
MDTV-Standard TKStd TKLCAF + TKCAF
Binary formats
BinLOcaf TKBinL TKLCAF
BinOcaf TKBin TKLCAF + TKCAF
BinXCAF TKBinXCAF TKLCAF + TKCAF + TKXCAF
TObjBin TKBinTObj TKLCAF + TKTObj
XML formats
XmlLOcaf TKXmlL TKLCAF
XmlOcaf TKXml TKLCAF + TKCAF
XmlXCAF TKXmlXCAF TKLCAF + TKCAF + TKXCAF
TObjXml TKXmlTObj TKLCAF + TKTObj

12. Shape Attribute
• TNaming_UsedShape: root label中描述整個framework tree
中所有使用到的topological shapes.
• TNaming_NamedShape: 描述TNaming_UsedShape屬性中
對應shape的變更演變過程資訊.
• Old shape代表操作變更前; new shape代表操作變更後的結果.
• PRIMITIVE: 建立新的shape; old shape = null.
• MODIFY: 對shape作變更.
• DELETE: 刪除; new shape = null.
• SELECTED: old = new.

13. Topological Naming
• Modeling操作歷程. Algorithm需要提供對所有操作對象
(entities/sub-elements)的存取功能.
• Result label, modeling algorithm操作結果需要儲存操作變更演變資訊
(old shapes and new shapes).
• 任何當前的shape/sub-shapes結果, 可被選取.
• Selector將選取結果儲存在SELECTED _NamedShape, 在幾何
物件經過操作變更後, 引用TNaming_Selector::Solve() API可
自動更新對應的被選取對象.
Result type Type of sub-shapes to be returned by history of algorithm
Solid or closed shell Faces
Open shell or single face Faces and edges of opened boundaries only
Closed wire Edges
Opened wire Edges and ending vertexes
Edge Vertexes
Compound or CompSolid To be used consequentially the above declared rule applied to all sub-shapes of the first level

14. Naming Example
• Nail(釘子) and translation functionality.
• 透過選取頂點(in Face1)決定選取某個釘子.
• TNaming_Selector::Select()指定並儲存一個selected shape.
• TNaming_Selector::Solve()找到原選取的Face1, 和對應的變更
evolution, 計算出變更後的結果Face1’.
• TNaming_Selector::NamedShape()獲得被選取物件變更後的狀態結果
(Face1’). 接著軟體可對Face1’做操作.

15. Standard Attributes
• TDataStd, TDataXtd, TDF packages.
• Geometric attributes: axis, constraint, geometry, plane, …,
PatternStd(linear, circular, rectangular, …).
• General attributes: ASCII string, extended string, integer, real, Tick
(boolean), array, list, …, variable, Uattribute.
• Relationship attributes: reference, reference array/list, tree node.
• Auxiliary attributes: directory, tag source.
• Standard or custom attributes?

16. Visualization Attributes
• 引用並實作AIS (Application Interactive Service)模組功能.
• TPrsStd_AISViewer class, 定義interactive viewer.
• TPrsStd_AISPresentation class, 定義label對應的顯示資料屬
性.
• 透過繼承TPrsStd_Driver class, 建立開發者自訂的
presentation driver.

17. Function Service
• TFunction package. 提供函式功能與演算法之間的連結.
• TFunction_Function: 儲存function driver的連結屬性. 由
TFunction_Driver::Execute() 執行功能變更步驟.
• TFunction_Logbook: 儲存受function影響的label集合. Drivers由此存
取到一個function對應的參數對象 (arguments).

18. Function Service Example
• Create a rectangular planar face F with height 100 and width 200;
• Create prism P using face F as a basis;
• Create fillet L at the edge of the prism;
• Change the width of F from 200 to 300;
• Solver for the function of face F starts;
• Solver detects that an argument of the face F function has been
modified;
• Solver calls the driver of the face F function for a regeneration of the
face;
• 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;
• Solver detects the function of P – it depends on the function of F;
• Solver calls the driver of the prism P function;
• Driver rebuilds prism P and adds the label of this prism to the logbook
as impacted;
• Solver detects the function of L – it depends on the function of P;
• Solver calls the L function driver;
• Driver rebuilds fillet L and adds the label of the fillet to the logbook as
impacted.

19. Function Mechanism
• Nail: defined by 1 cone, 2 cylinders, the nail. 4 functions.
• 函式機制系統建立函式間的依賴圖, TFunction_Iterator class
依序走訪各個函式.
• 開發者實作TFunction_Driver class:
• Arguments()回傳函式對應參數對象.
• Results()回傳函式的結果對象.
• Execute()執行該函式.

20. XML Support
• 支援XML file I/O.
• 限制:
• No unicode support.
• 移除部分API: getPreviousSibling(), getParentNode().
• 不支援DTD.
• Types: LDOM_Element, LDOM_Attr, LDOM_Text, LDOM_Comment,
LDOM_CDATASection available only.
• 不支援namespaces. 使用prefixed names.
• 不支援DOMException.
• 不是重點, 懶得詳細整理了~