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Re: XML Schema Question

From: <noah_mendelsohn@us.ibm.com>
Date: Tue, 24 Aug 2004 17:35:19 -0400
To: Jeni Tennison <jeni@jenitennison.com>
Cc: Mik Lernout <mik@futurestreet.org>, xmlschema-dev@w3.org
Message-ID: <OF67A50427.7C78CA77-ON85256EFA.004894E5@lotus.com>

Jeni Tennison writes:

> My philosophy is that the main things that
> should influence the design of a markup language
> are (...): human readability, size, processing
> efficiency, and extensibility.

> It seems foolish to artificially constrain a 
> markup language because of the weaknesses of
> one particular schema language

I agree, for the most part.  On the other hand, I think you have perhaps 
underemphasized fidelity of the markup to the underlying semantics of the 
information to be processed.  Thus, independent of schema language,  one 
can argue that:


is more robust than:

<list>val1 val2 val3</list>

Tools like XQuery/XSL will have an easier time picking up the explicit 
markup of the more verbose form.  Though I can see it either way, one can 
make the case in that spirit for the following "improvement" to the 
example in question:



Suggested improvement:


Though I'm sure you would get differing opinions from various members of 
the XML Schema WG, I think it's fair to say that among the reasons we did 
not invest more in the "unordered sequences of elements with count 
controls on each element by name"-model was a feeling that in the majority 
of cases such markup is in fact undesirable.  We could have extended 
<xsd:all> to support this, but chose not to in release 1.0. We do 
occasionally get requests to add such function, but some of us remain 
unconvinced that it is a high priority.  You'll note that XML Schema can 
easily model my "improved" form, either using <xsd:sequence> (order of the 
sections matter) or <xsd:all> (if it doesn't).

In any case, independent of the schema language used, I think there are 
often better alternatives to examples such as the one that inspired this 

Noah Mendelsohn 
IBM Corporation
One Rogers Street
Cambridge, MA 02142
Received on Tuesday, 24 August 2004 21:36:42 UTC

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