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Re: RE : Comparison of Xml documents

• To: John Cowan <cowan@m...>
• Subject: Re: RE : Comparison of Xml documents
• From: Bob Foster <bob@o...>
• Date: Sat, 22 Nov 2003 21:15:53 -0600
• Cc: Bob Wyman <bob@w...>, 'GARNIER Pierre' <pgarnier@m...>,'Alaric B Snell' <alaric@a...>, xml-dev@l...
• In-reply-to: <20031123022618.GL26171@m...>
• References: <3FBF38A1.9060908@o...> <002501c3b116$f987a880$650aa8c0@BOBDEV> <20031123022618.GL26171@m...>
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John Cowan wrote:
> Bob Wyman scripsit:
>>It would have been wise if the WXS designers had noted existing
>>standards and used "SET" rather than "SEQUENCE" when defining WXS...
> 
> There's a reason behind that: the schema-centric viewpoint on this point
> is opposed to the data-centric viewpoint.  In general, if a schema says
> that the order is prescribed (a sequence), that means that there is no
> significance in the order.  On the other hand, if the schema does not
> prescribe an order, then there is typically significance in the ordering
> that actually appears in the data.  WXS takes a schema-centric viewpoint;
> ASN.1 takes a data-centric one.

As was pointed out earlier, the "schema-centric" view is missing the 
ability to say, for elements, that no order is prescribed and order is 
not significant. Same semantics as attributes.

OTOH, if a schema prescribes an order (a sequence) it is moot that there 
is no significance in the order, as the prescribed order must be observed.

Further, the schema-centric viewpoint you describe is definitely not the 
common usage for iterated choices, e.g., (a|b|...)*. In this case, no 
order (or cardinality) are prescribed and the semantics is usually that 
order is not significant.

Bob Foster

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