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[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] Re: Inheritance and other buzzwords
 From: james anderson <James.Anderson@m...> > there were some things in a remark yesterday from Rick Jelliffe and in a note > from Peter Murray-Rust which lead me to doubt that wd-xml-names will work unless > it is extended to more completely specify the semantics of the namespace > declaration pi. I think the wd-namespace will work as advertised, but I think a lot of people will try to use it for more than the uses that it pupports to address. Following are some general comments. > in previous remarks, it has been explained that the wd expressly avoids > specifying a semantics. 1) Some people claim that the difference between a hyperlink and an entity declaration/reference is that there is something voluntary or contingent about a hyperlink while an entity declaration/reference expresses a more fixed and necessary relationship. If we accept that for a second, then I think Andrew's comments are clearer: the schema nominated in the namespace declaration is not "specified" rather it is "identified". So namespace PI is more like a hypertext link rather than an entity reference. Some people think that, in the long run, document-specific type structures will be declared (using XML-data or XML markup declarations) in the document, while external-vocabulary schema fragments will be defined externally, invoked using the namspace PI. (I think it is more likely that names borrowed from HTML schema will be unprefixed, while all others will be.) In that case, namespace PIs act more like a kind external entity reference--more like the ISO "module" proposal. 2) I think the term "scope" shouldn't be used here: all namespace PIs have scope over the entire document, not over particular entities. And an element type name without a prefix has no binding to a schema using the namespace mechanism (it still could use the standard XML markup declarations, or architectural forms, or ICADD fixed attributes, or other home-made systems though.) 3) My point about namespace PIs having the same prefix is merely that without the namespace PI there is the possibility of a clash with every name. The namespace PI does not guarantee name uniqueness accross all documents, it merely decreases the number of clashes. This is pretty weak in my book, but it is workable provided developers understand it and write their software accordingly. With the wd-namespace PI the number of possible things that can clash is reduced to the prefixes themselves and to unqualified names. And the prefixes give corporate and project names, not common element names: it is very easy to predict that two documents will have incomptible element types named "table", not so many documents will have incompatible namespaces called "rdf" (except for the versioning issue mentioned previously). Of course, it would be much better to have "w3.org-rdf" as the prefix, since that would introduce some discipline. Certainly if I ever use namespace PIs I would try to make sure that my prefix had some robustness to it, by including an organization name in it. Rick Jelliffe 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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