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Validation of a CGM Graphic Against the Web CGM Profile Stuart Galt The Boeing Company.

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Presentation on theme: "Validation of a CGM Graphic Against the Web CGM Profile Stuart Galt The Boeing Company."— Presentation transcript:

1 Validation of a CGM Graphic Against the Web CGM Profile Stuart Galt The Boeing Company

2 Agenda What is the WebCGM profile The process Hard parts

3 WebCGM CGM (ISO 8632) vector and composite vector/raster graphic format. WebCGM is a profile used to specify the subset of the CGM standard that will be used to exchange data on the web.

4 WebCGM History 1987 - ISO approved CGM as a Standard 1995 - CGM became a registered mime type 1996 - W3C published Scalable Graphics Requirements 1997 - W3C published Use of CGM as a Scalable Graphic Format 1999 - WebCGM 1.0 approved in January

5 WebCGM is intelligent Contains graphic primitives –Lines, polylines, polygons –Rectangles, circles, ellipses, arcs –Graphical text Non graphical content –Metadata –Hierarchies objects –Links

6 The Process

7 CGM to XML CGM graphic primitives are converted directly Containers are used to represent internal state changes

8 CGM primitives Circle centered (4252, 2385) radius 150 Binary CGM 41 86 10 9c 09 51 00 96 XML

9 CGM primitives (contd) Restricted Text NOTE:

10 CGM primitives (contd) Polygon

11 CGM States Container elements used to mark state changes –Metafile defaults …defaults go here …

12 CGM States (contd) –Picture Descriptor and Picture Open State Picture Description …Picture descriptor data here… …Picture data here…

13 Computer Graphics Metafile BegMF Picture EndMF Picture BegPic Picture Body EndPic Picture Body BegPicBody Metafile Descriptor Picture Descriptor Picture Open CGMStates

14 Metafile Decsriptor MFVersion MFDescVDCType FontList IntegerPrec CharSetList RealPrec CharCoding IndexPrec NamePrec ColrPrec MaxVDCExt ColrIndexPrecMaxColrIndexColrValueExtMFElemlist SetPriExtColrModel ColrCalibFontProp GlyphMapSymLibList opt rep MetafileDescriptor

15 Validating WebCGM Current state: –Profile validation tool exists for WebCGM in binary encoding Metacheck –With a WebCGM schema defined General purpose tools would be available

16 The Schema Some elements are easy to represent Some are hard

17 Metafile Version ...other required elements go here...

18 Non Graphical Text String

19 The Hard Some elements are restricted (or required based on the value of the metafile version –If version == 3 then a RestrictedTextType element must appear before the first RestrictedText element –If ColorSelectionMode is indexed color is index value, else color is RGB values

20 The Hard Part Branching logic –If (condition a) then foo else bar

21 Conclusion Creation of a schema that enforces WebCGM profile allows simple XML schema validator to validate conformance of CGM graphics. This approach could also be used to simplify validation of other binary structured formats.

22 Whats Ahead Complete mapping CGM binary to XML Finish WebCGM schema Work to continue in CGM Open Consortium: http://www.cgmopen.org


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