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RE: xPath 2.0, XSLT 2.0 ... size increase over v1.0

• To: Michael Kay <michael.h.kay@n...>
• Subject: RE: xPath 2.0, XSLT 2.0 ... size increase over v1.0
• From: Murali Mani <mani@C...>
• Date: Wed, 11 Jun 2003 14:37:01 -0700 (PDT)
• Cc: <xml-dev@l...>
• In-reply-to: <001901c33060$9b2b5d90$6401a8c0@pcukmka>

On Wed, 11 Jun 2003, Michael Kay wrote:

> 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
> us?

You are right that these are about sequences. I will try to do that below.
a^n b^n means:

a is <a/>
b is <b/>

a^n means sequence of any number of <a/>

a^n b^n means sequence of any number of <a/> followed by sequence of the
*same* number of <b/>

The sequences which conform to this are:

empty sequence, <a/><b/>, <a/><a/> <b/><b/> ... etc

You cannot write an XML schema/regular tree grammar for this output..

In my example, when I say S -> s (A, S, B) can be read as

<!ELEMENT a (a, s, b)>

S -> s (A, S, B) | s () can be read as

<!ELEMENT s (a, s, b)?>

A -> a () can be read as

<!ELEMENT a EMPTY>

cheers and regards - murali.

> 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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  • RE: xPath 2.0, XSLT 2.0 ... size increase over v1.0
    • From: "Michael Kay" <michael.h.kay@n...>

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