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Re: XQuery -- Reinventing the Wheel?

• From: "Thomas B. Passin" <tpassin@h...>
• To: xml-dev@l...
• Date: Thu, 22 Feb 2001 00:25:33 -0500

Evan Lenz wrote -

>
> After reviewing the XQuery spec, I'm concluding that the overlap between
> XQuery and XSLT is far too great for the W3C to reasonably recommend them
> both as separate languages. If XSLT (or XSLT 2.0) isn't considered adequate
> as an XML query language by itself, then the development of an XML query
> language should still build from the same semantic and syntactic base as
> XSLT.
>

Oh, no, I don't see this at all.  I see it in a very different way.  XQuery is
built on a model that includes a graph-like  info set, a system to navigate
around the graph, a system to specify and evaluate expressions of a type not
included in XPath/XSLT, a type system, and a query algebra.  Only the
navigation part is like XPath (it virtually IS XPath).  And this is as it
should be - if you need a tree or "forest" navigational system, use XPath
(extended if need be).

XSLT is valuable as a query language for certain types of queries, given that
we don't yet have a standard query language.  But it's very weak as a general
query mechanism.

Me, I like a lot of what I see in the draft XQuery documents.  I'm really
puzzled, though, by what seems to be invalid XML illustrated in several
places.  For example, in the XQuery langugage draft:

---------------------------------------------------------
(Q8) Generate an element with a computed name, containing nested elements
named <description> and <price>.
<$tagname>
   <description> $d </description> ,
   <price> $p </price>
</$tagname>

-----
The following example shows how an element constructor can be used to create
an element whose name and/or attribute-name is the same as a XQuery keyword:

<'FOR' 'LET' = "WHERE"/>
---------------------------------------------------------

I don't understand how expressions like these are supposed to appear in a
valid XML document.  There's nothing I noticed about escaping such
expressions.

Cheers,

Tom P

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