- From: <noah_mendelsohn@us.ibm.com>
- Date: Mon, 10 Jun 2002 13:49:30 -0400
- To: Tim Bray <tbray@textuality.com>
- Cc: www-tag@w3.org, jjc@jclark.com, murata@hokkaido.email.ne.jp
James Clark writes in the first of the notes referenced by Tim [1]: >> Certainly there is a need to be able to associate a >> schema with a document. We discussed this during >> the development of RELAX NG, but we reached the >> conclusion that it was better not to include this >> functionality as part of the schema language. ...and then he goes on to list some of the good reasons... As it turns out, we considered many of the same factors in desiging W3C XML schemas. We came to very similar conclusions and for similar reasons. Indeed, we took a lot of heat for not more tightly tying schemas to documents and/or namespaces. Anyway, the base architectural principle in W3C XML schema is that there is no fixed association between instance and schema documents. Processors and applications are free to validate any document (indeed any element information item) against any schema appropriate to the needs of the application. I infer that RELAX NG does the same. W3C XML Schema does offer an xsi:schemaLocation attribute for inclusion in instance documents. Its use is optional, and even if present it is only a hint. So a document author can say, "here's a schema you might consider", but he or she cannot mandate its use. Regarding the need to support multiple schema languages: the fact that xsi:schemaLocation is in a schema-defined namespace suggests that it is particular to the W3C schema language. If RELAX NG had its own such attribute, you could use that in the same docuemnt to locate RELAX schemas (of course, there would be the issue of making each schema accept the others' attributes.) So: I think those who worked on W3C schemas and those who worked on RELAX NG have arrived at somewhat similar conclusions, which is reassuring. (BTW: I claim no expertise in RELAX NG details). Thank you. [1] http://lists.xml.org/archives/xml-dev/200206/msg00274.html ------------------------------------------------------------------ Noah Mendelsohn Voice: 1-617-693-4036 IBM Corporation Fax: 1-617-693-8676 One Rogers Street Cambridge, MA 02142 ------------------------------------------------------------------ Tim Bray <tbray@textuality.com> Sent by: www-tag-request@w3.org 06/09/2002 04:05 PM To: www-tag@w3.org cc: (bcc: Noah Mendelsohn/Cambridge/IBM) Subject: Two messages from James Clark that ought to be read from xml-dev: http://lists.xml.org/archives/xml-dev/200206/msg00274.html http://lists.xml.org/archives/xml-dev/200206/msg00275.html -Tim
Received on Monday, 10 June 2002 14:08:18 UTC