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RE: Betr.: RE: requesting XML records

From: Matthew Dovey <matthew.dovey@las.ox.ac.uk>
Date: Fri, 28 Mar 2003 10:38:38 -0000
Message-ID: <149B1E6A2147804D9651886835D1999A2007FC@sers004.ouls.ox.ac.uk>
To: "Theo van Veen" <Theo.vanVeen@kb.nl>, <mike@indexdata.com>, <a.powell@UKOLN.AC.UK>
Cc: <www-zig@w3.org>

We already have such a URI - the namespace URI.

As far as I can see we have people who want to request a record which
conforms to a given structure i.e. request by schema, others who want a
record containing certain elements i.e. which uses (non-exclusively) a
particular namespace in the way DC works. A possible problem arises if
the same URI is being used for both - which is why I feel some way of
saying whether you are requesting by schema or by namespace is needed
(and ComSpec seems to have this in Z39.50 v3).

The distinction I think is comparable to GRS.1, as to whether you want a
record which uses particular tag-sets or a record which comforms to a
particular profile such as GILS.

Matthew



> 
> -----Original Message-----
> From: Theo van Veen [mailto:Theo.vanVeen@kb.nl] 
> Sent: Friday, March 28, 2003 9:06 AM
> To: mike@indexdata.com; Matthew Dovey; 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 05:38:40 GMT

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