Re: [xml-dev] Will the next version of XML Schema have a schema-for-sche

["Anthony B. Coates (XML-Dev)" <abcoatesecure-xmldev@yahoo.co.uk>]

Rick, is that historically correct?  Was anyone in the XML Schema Working  
Group ever arguing *for* content models that depend on attribute values or  
similar?  I wasn't there, but W3C XML Schema (to me) has always looked  
like a schema language which takes a lot of inspiration the way data is  
structured in object-oriented languages (and to a lesser extend,  
relational databases).

That is to say, I didn't think it was a case of "they did it this way  
because they were forced to", I always thought it was more "they did it  
this way because they chose to", which is a different kettle of fish.

Cheers, Tony.

On Thu, 18 Oct 2007 09:14:31 +0100, Rick Jelliffe  
<rjelliffe@allette.com.au> wrote:

> In XSD, for example, the use of elements to describe complexContent and
> simpleContent is jarringly odd and unpleasant, and it comes from the
> fact that XSD cannot use attributes to select a content model. Elements
> is all it has in this situation.
>
> Therefore, in XSD anything that impacts the content *must* be described
> using (ultimately) the element name, not an attribute. (@xsi:type is a
> special case.) So when using XSD, you cannot use attributes to be
> attributes that specialize the generic identifier, you have to use very
> specific identifiers. It is no advance on 1986 DTDs.
>
> This is because XSD really thinks of attributes as being funny
> sub-elements, rather than the element name being a funny truncated kind
> of attribute (which is the "architectural" view). And it is because
> there is no way for the children of an element to determine the
> effective type of the parent (err, except for the special and partial
> case of derivation by union.)
>
> Cheers
> Rick Jelliffe
-- 
Anthony B. Coates
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