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Re: [xml-dev] RE: Difference between "normalize" and "canonicalize"?
To: "'xml-dev@-----.---.---'" <-------@-----.---.--->
Date: 2/26/2009 6:21:00 PM
At 2009-02-25 19:22 -0500, I wrote: >At 2009-02-25 19:03 -0500, Costello, Roger L. wrote: >>1. Why is the Schema non-normative? > >Because the semantics of the schema language used, W3C Schema 1.0, >are not rich enough to express all of the constraints for XSLT as an >XML vocabulary. I believe the RELAX-NG schema semantics are rich enough. Based on the flak I've had to deflect in off-list private correspondence from a number of people regarding my statement above, please accept my apology if my intent was misunderstood. I (mis?)interpreted Roger's post to be in regard of using schema-aware tools to analyze the presence and absence of elements and attributes in an XML document, such as would be the role of a generic XML editor. My experience with XSLT and emacs and RELAX-NG is that I have yet to find any constraints in the presence and absence of elements and attributes allowed by the XSLT 1.0 and 2.0 vocabularies, such as the co-occurrence constraints I cited for attributes: >For a definitive example, one cannot express in W3C Schema 1.0 >semantics that two attributes are mutually exclusive or mutually >non-exclusive. For example, in an XSLT template rule you can have >either a match= attribute or a name= attribute or both but not >neither. You can say this in RELAX-NG-speak but not in W3C-Schema-speak. I thought I was explicit when I said "all of the constraints for XSLT as an XML vocabulary". I wasn't saying "all of the constraints for XSLT as an XSLT stylesheet". And I added "as an XML vocabulary" expressly to indicate I was not talking about stylesheet constraints, only vocabulary constraints: the presence and absence of elements and attributes. I even gave an example of the kinds of constraints I was speaking of. Never would I expect any generic schema language to express the constraints on the semantic interpretation of values found within its elements and attributes. That is the purview of the applications interpreting the semantics of the instances. Forgive me for leaving the impression to some readers that I was lauding RELAX-NG for having such features. Those are not the purview of generic applications tasked with simple requirements (such as for editing XML documents) where the author is guided in avoiding the improper creation of instances based on explicit rules for the presence and absence of attributes. Seems to me to be a good role for schema constraints. I trust I've made my intent clear now ... I was only trying to help by sharing my personal experiences with XSLT, emacs and RELAX-NG that I thought were directly in line with Roger's inquiries. . . . . . . . . . . Ken -- XQuery/XSLT training in Prague, CZ 2009-03 http://www.xmlprague.cz Training tools: Comprehensive interactive XSLT/XPath 1.0/2.0 video Video lesson: http://www.youtube.com/watch?v=PrNjJCh7Ppg&fmt=18 Video overview: http://www.youtube.com/watch?v=VTiodiij6gE&fmt=18 G. Ken Holman mailto:gkholman@C... Crane Softwrights Ltd. http://www.CraneSoftwrights.com/x/ Male Cancer Awareness Nov'07 http://www.CraneSoftwrights.com/x/bc Legal business disclaimers: http://www.CraneSoftwrights.com/legal