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Subject: Re: [cgmo-webcgm] ISSUE: must conforming XCFs be validatable?
Hi Lofton, I thought about this some more and what you are in fact proposing is that a conforming XCF file must not only be "well-formed" (http://www.w3.org/TR/REC-xml/#sec-well-formed) but also a "valid XML document" (http://www.w3.org/TR/REC-xml/#sec-prolog-dtd ). From an authoring tool perspective, this may be difficult to achieve. It is easy to achieve when there is no metadata, but more difficult when there is metadata. I doubt authoring tool will always be in a position to extend the DTD so that the XML namespace metadata passes DTD validation. I think this could cause more damage than good when exchanging XCF files. What is an authoring tool suppose to do when he loads in a file with this at the top?: <?xml version="1.0" standalone="no"?> <!DOCTYPE ... [ <!ENTITY % grobjectExt "| customNS:customElement" > <!ATTLIST grobject xmlns:customNS CDATA #FIXED "http://www.example.org/customNS" customNS:customAttr CDATA #IMPLIED > <!ELEMENT customNS:customElement EMPTY> <!ATTLIST customNS:customElement xmlns:customNS CDATA #FIXED "http://www.example.org/customNS" info CDATA #IMPLIED> ]> Maintaining these DTD extension sounds like a lot of work on authoring tools for the only purpose of XCF versioning... I know you are very sensitive regarding feature creep, but this is a big one! This proposal is in fact a lot more work on vendors than most of the other proposals recently sent to the group. Why not simply say that: a conforming XCF file must specify its version either by explicitly specifying the 'version' attribute or by including a DOCTYPE that references a webcgm DTD. Thoughts -- Benoit mailto:benoit@itedo.com Thursday, June 16, 2005, 7:54:20 PM, Lofton wrote: LH> [...oops, I goofed last time and sent it to list, instead of LH> Ben ... noproblem, I think the choices are clear enough and ready LH> for issuediscussion and resolution by the TC...] LH> WebCGM TC, LH> We resolved in 20050615 telecon that every conforming XCF LH> must identifyits version. That raised the question of "how", and LH> theproposal for the original issue was: MUST contain DOCTYPE LH> (w/internal DTD or external ref. to DTD) and SHOULD also use LH> 'version'attribute on <webcgm>. This "how" issue hides amore LH> fundamental issue: must every conforming XCF contain DOCTYPEthat LH> defines or references its DTD, i.e., be validatable. LH> The answer will mostly determine the answer to "how" every LH> XCFidentifies its version. So we agreed that I would circulate LH> the newissue, split out from the original issue. LH> ISSUE: must every conforming XCF contain DOCTYPE that defines or LH> references its DTD? LH> ALTERNATIVES: LH> Alt.1: YES. LH> Alt.2: NO. LH> Recommendation: Alt.1, YES. LH> Regards, LH> -Lofton. LH> ----- original issue, resolved "must identify version"----- LH> At 04:40 PM 6/9/2005 -0600, Lofton Henderson wrote: LH> Source: Editors. LH> ISSUE: must every XCF instance identify its version? LH> In ch.4, the examples 4.1, 4.2, 4.3 show <webcgm> tags LH> without'version' attributes. The examples also start and end with LH> the<webcgm> and </webcgm> tags (except 4.2 with a piece LH> ofinternal DTD subset defining an extension element, which btw LH> looks to melike wrong syntax.) The examples do not show the XML LH> declaration,and do not show a DOCTYPE (which presumably would LH> contain an externalreference to the WebCGM XCF DTD.) [Side LH> suggestion: make theexamples be complete xml files.] LH> In 4.2, the DTD defines: version CDATA #fixed 2.0 LH> So if the XCF instance contained a DOCTYPE referencing the LH> DTD, theversion would be defined. (#fixed means: if 'version' LH> ispresent, it must be 2.0; if not present, 2.0 is the default). LH> If an XCF instance contains neither a DOCTYPE nor 'version' LH> attribute on<webcgm>, then its version is unknown. LH> Question. Is WebCGM 2.0 going to allow such un-versioned XCFinstances to be conformant? LH> Alt.1: no, fix the current ch.4 text. LH> Alt.2: yes LH> RECOMMENDATION: Alt.1, no -- every conforming XCF must somehowidentify its version. LH> If Alt.1 is accepted, then "how"? There are several waysto LH> achieve it, here's one proposal... LH> PROPOSAL. 1.) Require that every conforming XCF must contain LH> aDOCTYPE referencing its DTD (and may also have internal DTD LH> subset forextensions, of course). And, 2.) Recommend that the LH> 'version'attribute be used on the root element (<webcgm>). I know LH> that#2 is redundant with #1, but there are circumstances and LH> scenarios whereit is convenient to have the information there in LH> the XCF instance,instead of in some remote referenced resource LH> (the DTD). LH> Regards, LH> -Lofton.
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