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Subject: Re: [cgmo-webcgm] Model Profile version in Chapter 6?
Hi Rob, Taking your questions a little out of order: At 12:16 PM 8/26/2005 -0600, Robert Orosz wrote: >[...] >I have a vague recollection that an earlier version of the Model Profile did >not require clamped splines which leads me to wonder, are we listing the >latest Model Profile in Chapter 6? Yikes! I just checked my paper copy [1] of ISO 8632:1999 Part 1, Annex I (PPF). In the MP, it is the clamped form. This agrees with the ISO-hosted online (PDF) version at [2]. It agrees also with p1.htm, which is an unofficial HTML version that was given to me by ISO and which I have in my old editor's directories. So "clamped" must be considered to be the latest MP PPF. [1] paper CGM:1999 [2] http://isotc.iso.org/livelink/livelink/fetch/2000/2489/Ittf_Home/PubliclyAvailableStandards.htm [3] p1.htm It does NOT agree with the MP of WebCGM 1.0 [4], nor with draft 2.0 [5]: [4] http://www.w3.org/TR/REC-WebCGM/REC-04-CGM-Profile.html [5] http://www.oasis-open.org/committees/download.php/14161/WebCGM20-20050804.zip It's hard to guess where this happened. But I recall, in the foggy past (probably about 6 years ago), we changed the PPF format from check- box style to YES/NO on the Required/Permitted/Prohibited line (to avoid the funny empty-box and checked-box characters in the WebCGM HTML text). Someone must have made the error then (let's blame John!). The good news: since 1.0 didn't allow NUBS/NURBS, the error in transcription of the MP doesn't affect 1.0. We do need to consider whether we want to restrict to the clamped form for 2.0 (seems reasonable -- the clamped cubic NUBS/NURBS would be a subset of all cubic ones, which should mean easier viewer implementation. Does "clamped" suffice for the potential users?). The bad news: did ATA propagate that MP error? and, are there other MP PPF errors? >I'll try and review more of the PPF to >see if there are other inaccuracies. That would be terrific -- very timely and much needed now. (If you are unable to do it, please let me know -- we'll need to give it as an AI assignment to someone.) >I have an open action item to generate some test cases with NUBS for the >test suite. In preparation for doing so, I went to sections T.19.24 and >T.19.25 of the WebCGM PPF to review the requirements. Both sections state >"Same as Model Profile: Yes", however, the Model Profile half of each >section is incorrect. The Model Profile requires clamped splines which >means that the first four knots must be identical and the last four knots >must be identical. This requirement is not listed in the WebCGM 2.0 draft >PPF. Section 6.1 does say, "In case of discrepancies, the Model Profile in >ISO/IEC 8632:1999 shall take precedence." however, I suspect most people >won't take the time to cross check with the Model Profile. Probably not. However, as I said -- the normative content of WebCGM 1.0 is unaffected. And in any case, the "discrepancies" clause means that (formally) "clamped" rules in the MP column. We will of course fix the content of the MP in the 2.0 PPF. If anyone thinks that 2.0 should NOT be "same as MP" (i.e., that we should remove the "clamped" restriction of the MP), he should bring it up as an issue. Thanks, -Lofton.
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