W3C home > Mailing lists > Public > xmlschema-dev@w3.org > December 2004

Re: target namespace and namespaces

From: Dan Vint <dvint@dvint.com>
Date: Fri, 03 Dec 2004 08:39:18 -0800
Message-Id: <>
To: xmlschema-dev@w3.org

Ok, so maybe this is allowed by schema mechanisms and might even work with 
particular tools sort of. Too me, listing multiple locations for a schema 
is sort of the catalog approach to find a single schema, not allow a 
substitution of a variety of schemas. This seems very ugly from say an XSLT 
standpoint, now instead of having a stylesheet that works with one subset 
of the elements, I have to have a schema that basically recognizes them all 
- makes management of the stylesheet more difficult.

Is the idea of having multiple schemas under one namespace what was 
intended and do others think this is a good use or an abuse of the 
namespace mechanism?

What about using one file out of a schema comprised of a number of files?


At 08:00 AM 12/3/2004, Jeff Rafter wrote:
>>In the Namespace spec I can't see any guidance on this question and with 
>>the schema spec saying schema location information is optional and at 
>>best a hint I don't see any help there either. With the schema location 
>>info being a "hint" there seems to be no way to make clear that I would 
>>want namespace foo with schema 1 rather than schema 2. So I lean towards 
>>this not being necessarily illegal, but a REALLLLLY poor design.
>As Xan said, your assumption about <include> was incorrect-- you can 
>include items in the same namespace. This leaves you three options as near 
>as I can tell:
>(1) Create a "driver" or "master" schema-- this does nothing more than 
><include> your two divergent but like-namespaced schemas. Now you are back 
>to one schema, which you prefer.
>(2) Include more than one schema in the schemaLocation hint
>   xsi:schemaLocation="http://foo schema1.xsd
>                        http://foo schema2.xsd"
>Unfortunately support for this is spotty.
>(3) Use some other out of band mechanism. For example in Xerces or MSXML 
>you can list multiple schemas to be used for validation. Additionally 
>there is RDDL which allows you to identify which schemas can be used to 
>validate items coming from a particular namespace (XSV supports this but 
>again support for this is not very common) or use NRL (namespace routing 
>language) which should allow you to do exactly what you want. Of course I 
>haven't seen support for NRL in any XML Schema processor...
>So of these... option (1) is the most stable.
>Jeff Rafter

Danny Vint

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Received on Friday, 3 December 2004 16:37:33 UTC

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