[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] Re: Namespaces need versioning
From: David Brownell <db@E...> Date: Fri, 16 Oct 1998 18:35:19 -0700 Subject: Re: Namespaces need versioning David Brownell wrote: > Actually, the quote was from me. Oops. Thanks for the correction. >>David Brownell wrote: >> > >Namespaces need versioning. URIs can easily include date >> > >codes like "02Nov1997"; W3C itself uses such a scheme, as >> > >you can see by looking at versions of the namespace spec. >> >> Charles Reitzel wrote: >> Yes, the FPI and/or URL needs versioning. With a decent namespace >> spec,the prefix used in documents should not. The fact that the prefix >> is, for all practical purposes, a public identifier, controlled by the >> DTD author, and tied to a specific verion of the DTD, prevents document >> authors from changing DTD versions without rewriting their documents. >> - Not useful. >> >> The original namespace WD did not have these flaws. > >I don't see what you're saying. All versions of the namespace spec >have used the URL as _just_ an identifier. The identifiers need to >reflect an exact set of meanings, hence they need versioning. The >prefix was chosen and used by the document author, hence needed no >more versioning than the document itself: "this version", versus >the case of the namespace URI (meaning defined by a third party, and >updated/maintained/changed over time), "the version before that big >incompatible change". > >That is, I don't see an issue that's tied only to the _new_ draft >of namespace support, or even one that could be removed. The difference is that for a prefix to be set in a DTD it has to be a #FIXED attribute of the element and is, therefore, defined by the author of the DTD and *not* the document. If the prefix is set by the document author, then the exact, version-specific URL must also be included with each instance of the element using the prefix. In the first case, the prefix must also be version specific and, therefore, cannot be used as a mechanism to insulate documents from changes in the DTD version. In the second case, when the DTD version changes, every instance of its use must be updated to refer to the new version of the DTD fragment. Remember, the purpose here is to define standard libraries of DTD fragments which can be used for industry specific EDI transactions, standard data types, and the like. Such DTD fragments will occasionally undergo updates which will be, by and large, backward compatible - much like standard function libraries. Typically, only a small number existing elements would be "broken" by the new DTD fragment. The document author simply has to change the prefix declaration to point to the new version of the DTD fragment and run the documents through the parser and/or application. With a well designed and maintained DTD fragment, only a few elements will be kicked out. With the old spec, the prefix is associated with a URL uniquely within a document and cannot mean different things for different elements. The prefix declaration occurs in the document prolog, possibly in an external entity (i.e. DTD fragment). Currently, the NS processing instruction is allowed as a custom, non-standard feature and may well not be inter-operable with other XML parsers or applications. That said, the processing instruction is *required* for validation to work (i.e. for an element instance to be correctly associated with its declaration by its qualified name). But all of this ground was well-trod by xml-dev'ers when the revised NS spec came out. See what I mean? Best regards, Charlie Reitzel Independent Consultant P.S. I sense a great deal of hesiation among industry groups hoping to base data exchange standards on XML DTD's due to this issue. Is everybody giving up on validation and moving to DCD instead? xml-dev: A list for W3C XML Developers. To post, mailto:xml-dev@i... Archived as: http://www.lists.ic.ac.uk/hypermail/xml-dev/ To (un)subscribe, mailto:majordomo@i... the following message; (un)subscribe xml-dev To subscribe to the digests, mailto:majordomo@i... the following message; subscribe xml-dev-digest List coordinator, Henry Rzepa (mailto:rzepa@i...)
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