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   RE: [xml-dev] Schema constraints from a different file?

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On Tue, 25 Oct 2005, Dmitry Epstein wrote:

>> Theoretically, I think this could do the trick:
>>   (1) Include the XML document that contains IDs into the document that
>>       refers to them via a parsed external entity [XML Rec, 4.2.2, 4.3]
>>   (2) Use WXS key/keyref feature [WXS, Part 1, 3.11] to encode your
>>       referential constraints.
>> (1) will physically keep the data in separate files, but the processor 
>> should pull them together, so the schema (2) could be written as if the 
>> data was present in a single file.
> Let me see if I understand.  The external entity could look like this:
> <item id="abc123"/>
> <item id="def456"/>
> ...
> Then in some other XML document the DTD will include these lines:
> <!ENTITY itemlist SYSTEM "itemlist.xml">

No need for the ATTLIST declaration, this constraint will be in your 

> and later in the body of the document:
> <items>&itemlist;</items>
> Something like this?
> But if I am already using a DTD to describe my document, can I use a schema 
> as well?

As Rick says, this will depend on the tool.  Since in this approach you 
need only the entity inclusion feature of DTDs, there is some hope that 
your schema-validating parser can do that...



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