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Re: requesting XML records

From: Mike Taylor <mike@indexdata.com>
Date: Thu, 27 Mar 2003 16:52:12 GMT
Message-Id: <200303271652.h2RGqCL17273@badger.miketaylor.org.uk>
To: a.powell@ukoln.ac.uk
CC: matthew.dovey@las.ox.ac.uk, www-zig@w3.org

> Date: Thu, 27 Mar 2003 12:46:54 +0000 (GMT)
> From: Andy Powell <a.powell@ukoln.ac.uk>
> 
> [Matthew's suggested solution to Theo's problem] sounds reasonable
> to me... but there is one thing that might be worth thinking
> about...
> 
> Is an application profile that uses 1 DC element and 50 IEEE LOM
> elements a 'loose simple DC' application or a 'loose IEEE LOM'
> application or both or either? ;-) The point being that the naming
> above (and Theo's DCX name) takes a very DC-centric view of the
> world.  Does this matter?

This is pretty much the point at which the discussion broke down when
we tried to thrash this out on the ZNG list.  Theo seems to have a
"pornographic" definition of a DC record: "I can't define it, but I
know it when I see it" :-)

So my stab at the general solution that I think we need is as follows:
we take a sort of OO approach to Schemas, declare that when a client
as for schema B, the server can return D where D is a derived class of
B.

Confused?  Don't be.  Take a nice, rigorous DC-simple schema.  My
client asks for DC-simple and the server gives it to me.  But if
instead it has DC-qualified records, and if DC-qualified is known to
be a subclass of DC-simple, then it's at liberty to give me those as
well.  Likewise, it could give me DC-plus-some-bits-from-IEEE-LOM
records provided that schema is a subclass of DC-simple.  (We'd also
want to send a bit in the present request saying whether this sort of
thing is acceptable, so that you can still ask for "DC-simple, dammit,
and none of your qualified nonsense!")

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?

 _/|_	 _______________________________________________________________
/o ) \/  Mike Taylor  <mike@indexdata.com>  http://www.miketaylor.org.uk
)_v__/\  "That which gets lost in translation" -- Robert Frost's
	 definition of poetry.

--
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Received on Thursday, 27 March 2003 11:53:45 GMT

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