[xquery-talk] Newbie Q: Namespace Handling

[Michael Rys]

That is because many of Google's tools (and other people, not to pick on Google alone here) have no clue of real XML namespace handling (well there are exceptions but this is a prime example).

Best regards
Michael

> -----Original Message-----
> From: talk-bounces at x-query.com [mailto:talk-bounces at x-query.com] On Behalf
> Of Sall, Kenneth B.
> Sent: Wednesday, May 02, 2007 3:54 PM
> To: Michael Kay; talk at x-query.com
> Subject: RE: [xquery-talk] Newbie Q: Namespace Handling
>
> Thank you, Michael. I will submit this to W3C.
>
> Meanwhile, I tried revising the basic KML (Google Earth) example at
> http://code.google.com/apis/kml/documentation/kml_tut.html#basic_kml
> to use a namespace prefix, like so:
>
> <?xml version="1.0" encoding="UTF-8"?>
> <ge:kml xmlns:ge="http://earth.google.com/kml/2.1">
>    <ge:Folder>
>       <ge:Placemark>
>          <ge:name>Simple placemark</ge:name>
>          <ge:description>Attached to the ground. Intelligently places
> itself
>        at the height of the underlying terrain.
>                 </ge:description>
>          <ge:Point>
>                         <ge:coordinates>-
> 122.0822035425683,37.42228990140251,0</ge:coordinates>
>          </ge:Point>
>       </ge:Placemark>
>    </ge:Folder>
> </ge:kml>
>
>
> Surprisingly, Google Earth thinks the root <kml> element is "missing or
> bad"! I'll try the other options you've suggested, especially (c).
>
> Ken Sall
>
> -----Original Message-----
> From: Michael Kay [mailto:mike at saxonica.com]
> Sent: Wednesday, May 02, 2007 6:18 PM
> To: Sall, Kenneth B.; talk at x-query.com
> Subject: RE: [xquery-talk] Newbie Q: Namespace Handling
>
>
> When you do
>
> <kml xmlns="http://earth.google.com/kml/2.1">
>
> the default namespace declaration affects the contained path expressions,
> so
> in
>
> doc("namespace.xml")//bar
>
> you are selecting bar elements in namespace
> http://earth.google.com/kml/2.1
>
> There's a good reason XQuery was done this way, it was an attempt to avoid
> the problems that people have with default namespace handling in XSLT 1.0,
> where a default namespace declaration *doesn't* affect unprefixed names in
> path expressions. But it makes it very difficult to handle your scenario,
> where the source document is in no namespace but you want result elements
> to
> be in a default (unprefixed) namespace. In fact it's because of this
> scenario that XSLT 1.0 was designed the way it was...
>
> I think this is a serious usability problem with XQuery 1.0 as defined and
> it needs to be addressed in XQuery 1.1. (Please feel free to file this as
> a
> comment against the spec - they carry more weight when they come from
> users.)
>
> In the meantime, I think your best option is probably to avoid using the
> default namespace in the result document: use a prefixed namespace
> instead.
> If you really need the result document to use the default namespace, then
> postprocess it to change the prefix.
>
> If you can't do that, some other possible workarounds are:
>
> (a) put the contained query
>
>     for $i in doc("namespace.xml")//bar return $i
>
> into a function or a variable where the namespace context can be different
>
> (b) use doc("namespace.xml")//*:bar
>
> which will select elements with local name "bar" in any namespace or none
>
> (c) generate the output elements with a computed element constructor
>
> element {xs:QName("kml")}{
>   element {xs:QName("Folder"){ {
>     ... etc ...
>
> Michael Kay
> http://www.saxonica.com/
>
> > -----Original Message-----
> > From: talk-bounces at x-query.com
> > [mailto:talk-bounces at x-query.com] On Behalf Of Sall, Kenneth B.
> > Sent: 02 May 2007 22:52
> > To: talk at x-query.com
> > Subject: [xquery-talk] Newbie Q: Namespace Handling
> >
> > Hello all.
> >
> > I've having difficulty outputting the correct default
> > namespace from a query. I'm using SaxonB 8.9J on Windows XP
> > with jre 1.6.0_01.
> >
> > With this trivial input:
> >
> > <?xml version="1.0" encoding="UTF-8"?>
> > <bar>foobar</bar>
> >
> > and trivial XQuery #1:
> >
> > <kml>
> >   <Folder>
> >       {
> >       for $i in doc("namespace.xml")//bar
> >       return $i
> >       }
> >   </Folder>
> > </kml>
> >
> > I get the result #1:
> >
> > <?xml version="1.0" encoding="UTF-8"?>
> > <kml>
> >    <Folder>
> >       <bar>foobar</bar>
> >    </Folder>
> > </kml>
> >
> > However, I want the opening <kml> to appear as:
> >
> > <kml xmlns="http://earth.google.com/kml/2.1">
> >
> > With XQuery #2:
> >
> > <kml xmlns="http://earth.google.com/kml/2.1">
> >   <Folder>
> >       {
> >       for $i in doc("namespace.xml")//bar
> >       return $i
> >       }
> >   </Folder>
> > </kml>
> >
> > I get result #2:
> >
> > <?xml version="1.0" encoding="UTF-8"?>
> > <kml xmlns="http://earth.google.com/kml/2.1">
> >    <Folder/>
> > </kml>
> >
> > Which isn't correct for the <Folder> content.
> >
> > I've also tried adding a default namespace declaration to XQuery #2:
> >
> > declare default element namespace "http://earth.google.com/kml/2.1";
> >
> > but that has no impact; I still get result #2.
> >
> > What am I missing? Thanks in advance for any clarification
> > about namespace handling.
> >
> > Kenneth B. Sall
> > XML Data and Systems Analyst
> > Advanced Systems and Concepts
> > Science Applications International Corp. (SAIC)
> > 7125 Columbia Gateway Dr., Suite 250
> > Columbia, MD  21046
> > 410-953-7016 (office)
> > 410-300-2997 (mobile)
> >
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