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Subject: Re: SAX 2.0 enhancement proposal
At 12:10 2001 06 13 -0700, David Brownell wrote: >> The XML Catalog draft specification [3] describes several different entry >> types. Some entries are for resolving public identifiers, some are for >> resolving system identifiers. The system identifier entries are intended to >> be matched with the system identifier as it appears in the xml document >> being processed. > >Seems to me THAT is the problem, not SAX. > >The XML spec is quite explicit on this topic: "relative URIs are relative to the >location of the resource within which the entity declaration occurs" (4.2.2). >Those are the only contexts in which an XML parser needs to resolve URIs, >and there's no weasel-wording that would allow what that catalog spec is >intending to do. So I don't see why SAX should permit anything else, >unless the XML spec gets a substantive functional change there ... I disagree as does most of the XML Core WG. Clearly, some catalog resolution is necessary for public ids, so the XML spec does not prohibit that. The fact that a catalog aka entity resolver might be used to remap system ids is make clear by the E3 erratum that you can find at http://www.w3.org/XML/xml-V10-2e-errata#E3 >> Unfortunately, SAX 2.0 requires that system identifiers >> that are URIs are made absolute before calling the EntityResolver, thereby >> robbing the catalog processor of the opportunity to compare the system >> identifier with the catalog entries. > >Relative URIs are, classically, trouble. That is an arguable statement with no backing. Most people, including the authors of RFC 2396 (with includes Tim Berners-Lee) feel they are very useful. >They're very easily mis-understood, >since implicit context is easy to get wrong. I'll grant you that some things about URIs can be easily misunderstood, but being easily misunderstood is not a good argument against something. If you read RFC 2396 and/or the XML Base spec: ftp://ftp.ietf.org/rfc/rfc2396.txt http://www.w3.org/TR/xmlbase/ you'll find the explanation of how to absolutize relative URIs very explicit. Relative URIs are something that is used every day by many people. > Why is this catalog draft trying >to encourage/facilitate error-prone and complex idioms? Which, moreover, >are intended to violate the XML specification? > >I can understand that applications may want to define other rules for >resolving relative URIs found in application data; that's their privilege. >"xml:base" will presumably go to REC and support such usage. So >resolvers used in those contexts may want different APIs than the >one used by an XML parser, even beyond config/setup issues. > >(I vaguely recall that SGML, or at least SOCAT, may have taken a >different approach than XML has, in this respect. That doesn't seem >to me like a good thing to try carrying forward, if so. There were some >web-naive notions I remember not liking in SOCAT; they weren't >essential, and hence are better removed.) The SGML Open/OASIS catalog was very useful to many people, and there are a fair number of experts who feel it was a mistake not to include something like that in XML. The OASIS Entity Resolution Technical Committee has a number of non-Web-naive XML experts on it working to create an XML version of such a catalog that we think will be very useful to many people. You can find out more about the work at: http://www.oasis-open.org/committees/entity/ paul
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