[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] Re: Another look at namespaces
From: Tim Berners-Lee <timbl@w...> >From: Rick Jelliffe <ricko@a...> > >>The only information that properly belongs in a namespace is a list of >>names. > >That is not useful. I realize that the word "Namespace" (as the end result >fo the discussions of modules or docuemnt types or vocabularies or...) >may be an english word which does not convey this, but a >a namespaces is a language: a set of names plus a set of syntactic >constraints plus - to be useful - a meaning shared by writer and recipient. A name is useful by being available for use in a schema, document, program, query, stylesheet or language. That use may be merely to disambiguate <rick:zzz/> from <tbl:zzz/> where these unique elements are only used by a stylesheet to display some appropriate graphic. "The namespace name, to serve its intended purpose, should have the characteristics of uniqueness and persistence. It is not a goal that it be directly usable for retrieval of a schema (if any exists)." http://www.w3.org/TR/REC-xml-names/ s2 The spec clearly says that to be useful, a namespace URI does *not* have to identifiy anything. It only has to provide uniqueness and persistence. The first paragraph of the namespaces spec begins: "We envision applications of Extensible Markup Language (XML) where a single XML document may contain elements and attributes (here referred to as a 'markup vocabulary') that are defined for and used by multiple software modules. " Namespaces are concerned with vocabularies (lists with meanings, not schemas: the words "schema" and "language" were available and were *not* used). Schemas are constructed from vocabularies. >I have noone associated with W3C say that a "a namespace is a schema" Err, isn't that your position above? You say that a namespace cannot be merely a list of names but must be "a language: a set of names plus a set of syntactic contstraints" (sounds like a syntactic schema to me) plus "a menaing shared by writer and recipient" (sounds like a semantic schema). Indeed your whole first posting to XML-DEV on namespace concerned schemas and validity. "For example, you can run an xHTML document though any DTD you like if it suits your purposes, but if you want to check whether it is valid xHTML then you should use the xHTML schema which corresponds to the namespace URI." If the namespace URI is a schema URI, then the namespace is a schema. {In another posting} >Perhaps perception of it is clouded by the fact that XML 1.0 doesn't mention >namespaces at all, and XML NS does not mention schemas at all. >In other words, the specs -- having to only refer backwards in time -- >have not been good at pointing to how the future architecure will fit >together. No, perception is clarified by memories of how much effort and debate it took to get mentions of schemas taken out of the Namespace document. The early drafts were full of mentions of schemas. For example, http://www.w3.org/TR/1998/WD-xml-names-19980327 even says "local schema namespace", combining them. That the XML NS does not mention schemas is by intent: to avoid mixing up schemas and namespaces. When the XHTML draft uses three different namespaces for the same elements, it does just that. I note Shane P. McCarron's recent post "With regard to namespaces, IMO the work on Modularization is orthogonal to namespaces." If future modularized XHTML does not conflate schemas and namespaces, what is the "future architecture" that makes it so important to have three? 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/ and on CD-ROM/ISBN 981-02-3594-1 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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