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Schema 1.1 wishlist (was: [xml-dev] RE: Is schemaLocation just a hint in schema import?)

From: Paul Spencer <paul.spencer@boynings.co.uk>
Date: Tue, 24 Oct 2006 12:20:01 +0100
To: "C. M. Sperberg-McQueen" <cmsmcq@acm.org>
Cc: <xml-dev@lists.xml.org>, <xmlschema-dev@w3.org>
Message-ID: <NBBBIBMKFOFCNEBAKDPLMEMALGAA.paul.spencer@boynings.co.uk>

There is definitely confusion among tool vendors on imports and includes,
especially with regard to namespaces. These is my wish list for clearing up
some of it. It is based on extensive experience of creating and reviewing
schemas (and writing schema guidelines) for UK Government.

I see no reason why a namespace should not contain names created from
multiple schema documents. In fact, this is a very logical and modular way
of creating schemas. Currently, as has been pointed out, the behaviour is
undefined when a schema document xs:imports multiple other documents with
the same target namespace. Hence we have the messy work-around of
xs:including the required documents into another and then xs:importing that.

Another problem I come across is multiple levels of xs:including chameleon
schemas. The spec gets interpreted two ways. If schema document A (target
namespace nsA) xs:includes B (no target namespace) that itself xs:includes
document C (no target namespace), I would like it to be clear that all
global components exist in the namespace nsA. We discussed this here several
years ago. Some tools do not interpret it this way, instead leaving the
components of document C without a target namespace. This severely limits
the use of chameleon schemas (which some will regard as a good thing).

There are other problems of different interpretations by tool vendors that
relate to hierarchies of schemas. I am sure the spec could be clarified in
this area just by thinking in terms of more than two layers in a hierarchy.

Paul Spencer

> -----Original Message-----
> From: xmlschema-dev-request@w3.org
> [mailto:xmlschema-dev-request@w3.org]On Behalf Of C. M. Sperberg-McQueen
> Sent: 16 October 2006 22:25
> To: Dan Vint
> Cc: C. M. Sperberg-McQueen; Michael Kay; 'Antoli, Leo';
> xml-dev@lists.xml.org; xmlschema-dev@w3.org
> Subject: Re: [xml-dev] RE: Is schemaLocation just a hint in schema
> import?
> The Working Group is working as hard as we can to make XML Schema
> 1.1 clearer than 1.0, to fix bugs, and to add useful
> functionality.  Simplification in the form of eliminating
> features has proven to be a very hard sell -- almost everyone
> agrees that there are a lot of features no one would miss, but
> the lists people give don't converge.  Just this morning I had a
> conversation in which someone suggested that the easiest way to
> simplify the description of schema composition would be to
> eliminate xsd:redefine entirely.  They are probably right, as far
> as it goes, but if you are using redefine you might feel that
> that would be going about simplification the wrong way.
> best regards,
> --C. M. Sperberg-McQueen
>    World Wide Web Consortium
Received on Tuesday, 24 October 2006 11:20:16 UTC

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