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   Re: [xml-dev] FW: [ANN]: XQuery: A Guided Tour

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At 03:56 AM 9/30/2003, Rick Jelliffe wrote:

>Oh dear. What about Usage Scenario 5 of the XML Schemas Requirements[1]?
>     "Use schema to help query formulation and optimization.
>     A query interface inspect XML schemas to guide a user in the 
> formulation of queries.
>     Any given database can emit a schema of itself to inform other 
> systems what counts as
>    legitimate and useful queries."
>And the design requirement that the datatypes must "define a type system 
>that is adequate
>for import/export from database systems (e.g., relational, object, 

Well, as you know, I agree with you. If XQuery were to design its own 
optimal schema language, I doubt that it would have xsi:nil or key/keyrefs 
- features specifically provided for the sake of future query systems. I 
think it was unwise to try to guess what the query language might become 
later on.

>Other good quote, showing the false economy of non-modularity in big specs:
>* XQuery's design influenced by XML Schema's provision of
>   "a set of primitive types, a type-definition facility, and an 
> inheritance mechanism...
>    (and) the validation process... Nevertheless, members of the working group
>    attempted to modularize the parts of the language that are related to type
>    definition and validation, so that XQuery could potentially be used with
>    an alternative schema language at some future time."

I think this is important.



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