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   Re: [xml-dev] xml schema, types and uniqueness/key constraints

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Four approaches spring to mind:

A) Add constraints in <appinfo> elements, in terms of types, using your 
own language.
Then create a postprocessor that generates the equivalent constraints in 
terms of
some other schema language (WXS' integrity/uniqueness constraints, 
XLinkIt).  Validate using that generated schema.

B) Run your document through a transformation that converts all element 
names with
their type names. Then validate that against a WXS schema with 
uniqueness/integrity rules
written  using these type names as element names.

C) Fulminate & vituperate at appropriate intervals.

D) Go on holidays

Rick Jelliffe

Christian Nentwich wrote:

>we are currently looking at where uniqueness and key constraints can
>be applied to our schema.
>The problem is, the schema is semantically very rich, big on element
>reuse, and huge. As a consequence, most of the schema is expressed in
>terms of data types.
>There are a few constraints that have to hold for all instances of those
>data types, for example, "elements of type A must reference existing elements
>of type B", but schema lets you express key/uniqueness only *per-element*,
>not *per-datatype*. This is probably prohibitive from a schema management
>Is there any way around this, or a best practice approach to addressing


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