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Betr.: RE: requesting XML records

From: Theo van Veen <Theo.vanVeen@kb.nl>
Date: Fri, 28 Mar 2003 10:05:55 +0100
Message-Id: <se841e9f.094@mail.kb.nl>
To: <mike@indexdata.com>, <matthew.dovey@las.ox.ac.uk>, <a.powell@ukoln.ac.uk>
Cc: <www-zig@w3.org>

If there is not a way to express what we want in XML schema, why can't we express it in plain English and give it a URI.   
 
In plain English I can express it as:
DCX means that the XML records are encoding according to the DCMI guidelines and contain terms from the dc and dcterms namespaces. The records may contain terms from other namespaces when they could - within reason - not be expressed by terms from the dc and dcterms namespaces. It is recommended that as much as possible terms from DCMI registered elementsets are being used. 
I do not think deriving schemas from one another (redefine, import, substition) will help us.

The main functions of schemas are: 1) being a common agreement and 2) offering a mechanism for validation. The question is whether we want to put agreements in a schema when we actually cannot validate these agreements. But this would certainly not be a reason for not making the agreement and give it a name or a URI.

Theo



>>> "Matthew Dovey" <matthew.dovey@las.ox.ac.uk> 27-03-03 18:06 >>>

> The issue here seems to be, what do we mean by one schema 
> being "derived from" another?  Is there a ready-made answer 
> to this from the world of XML Schema?  Or do we have to 
> invent such a notion?

Not a direct mapping - in XML Schema we have redefines, import and
substitution groups.

Roughly speaking these work as:

Redefines - in this case I say that I take schema A, but for a
particular element x I say what structure I what it to be rather than
the structure given in schema A.

Import - If I import schema A into schema B, then at any point in the
structure I'm defining for schema B, I can introduce a structure
references in schema A

Substitution groups - I import Schema A, but say that for a particular
element x in schema A, I can in fact substitute an element y in defined
in schema B

Matthew
Received on Friday, 28 March 2003 04:08:24 GMT

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