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   RE: [xml-dev] xPath 2.0, XSLT 2.0 ... size increase over v1.0

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> Regarding mathematical properties: in particular, closure properties.
> The operations being closed under regular tree languages 
> might be desirable property..

XSLT/XPath is closed with respect to its own data model. I don't know
how XSLT's data model relates to a "regular tree language", and I'm not
familiar with notations such as (a^n b^n).

Is there any chance you could translate this into XML terminology for

The examples seem to suggest that your concerns are with queries that
generate a sequence of nodes rather than a single node. Sequences are
part of the data model, and the language is closed over this space.

Michael Kay
> I have seen two kinds of operations under which regular tree 
> languages are not closed.. that is the result is not a 
> regular tree language..
> (a) Consider the schema:
> S -> s (A, S, B) | s ()
> A -> a ()
> B -> b ()
> if we write a query like // (a | b) -- the result is (a^n 
> b^n) which is not regular tree language..
> (b) Consider
> S -> s (A*)
> A -> a ()
> consider the query
> for $x in //a
>    return <b/>
> for $x in //a
>    return <c/>
> the result is (b^n c^n)
> The question is has the new constructs in XPath made it not 
> closed or not.. It might have.. If someone has studied these 
> aspects, then we can know if XPath 2.0 is different from 
> XPath 1.0 in these respects also..
> cheers and regards - murali.
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