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*sigh*
Numerous bugs abound in my XQuery expression, corrected version follows
schema "urn:xmlns:example-com" at
"http://www.example.com/schema.xsd";
namespace ex = "urn:xmlns:example-com"
define function get_children(element ex:root $r)
returns element ex:child*{
$r/ex:child
}
get_children(<ex:root>{
document("http://www.25hoursaday.com/root.xml";)//ex:child
}</ex:root>)
--
PITHY WORDS OF WISDOM
Lynch's Law: When the going gets tough, everyone leaves.
This posting is provided "AS IS" with no warranties, and confers no
rights.
> -----Original Message-----
> From: Dare Obasanjo [mailto:dareo@microsoft.com]
> Sent: Wednesday, July 03, 2002 12:54 PM
> To: Rick Jelliffe; xml-dev@lists.xml.org
> Subject: RE: [xml-dev] XQuery and DTD/Schema?
>
>
> You miss my point which is understandable since most people
> don't have to deal with the aggravations of XML Query on a
> daily basis. Here's an example of where type inferencing
> breaks down. Given the following schema
>
> <xs:schema targetNamespace="urn:xmlns:example-com"
> xmlns:xs="http://www.w3.org/2001/XMLSchema";
> elementFormDefault="qualified">
> <xs:element name="root">
> <xs:complexType>
> <xs:sequence>
> <xs:element name="child" maxOccurs="3" />
> </xs:sequence>
> </xs:complexType>
> </xs:element>
> </xs:schema>
>
> And the following XQuery expression
>
> schema "urn:xmlns:example-com" at
> "http://www.example.com/schema.xsd";
> namespace ex = "urn:xmlns:example-com"
>
> define function get_children(element of type ex:root $r)
> returns element of type ex:child{
>
> $r/child
> }
>
>
> get_children(<ex:root>{
>
> document("http://www.25hoursaday.com/root.xml";)//child
> }</ex:root>)
>
> How do you statically infer the type passed to the
> get_children() function call? The correct answer is that you
> can't. So what is the best workaround? Push it to a dynamic
> evaluation like so
>
>
> get_children(validate(<ex:root>{document("http://www.25hoursad
> ay.com/roo
> t.xml")//child}</ex:root>))
>
>
> This example is relatively simple and could be made hairier
> by adding substitution groups or derived types.
>
> --
> PITHY WORDS OF WISDOM
> Lynch's Law: When the going gets tough, everyone leaves.
>
> This posting is provided "AS IS" with no warranties, and
> confers no rights.
>
>
>
> > -----Original Message-----
> > From: Rick Jelliffe [mailto:ricko@allette.com.au]
> > Sent: Wednesday, July 03, 2002 12:38 PM
> > To: xml-dev@lists.xml.org
> > Subject: Re: [xml-dev] XQuery and DTD/Schema?
> >
> >
> > From: "Dare Obasanjo" <dareo@microsoft.com>
> >
> > > Type inference can be ridiculously expensive and in some cases
> > > undecidable for complex types. Named typing and enforcing
> explicit
> > > casts by users via operations such as validate() are the
> > best option
> > > in creating something reasonably implementable and
> > understandable. Of
> > > course, these things are only issues because XQuery is
> > supposed to be
> > > "statically typed"
> >
> > Is inferencing always that difficult?
> >
> > If we assume DTDs, then we have both a kind of Unique
> > Particle Attribute rule and no local elements or equivalents.
> > If the DTDs were
> > namespace aware and allowed declarations of the WXS builtin
> > datatypes, it seems pretty trivial to annotate a query with
> > the correct casts.
> >
> > If we have local elements, then the path in a query would
> > have to also be augmented with enough of a path to ensure
> > locality, and other definitions of the same element name
> > would have to be similarly augmented so they exclude the
> > local element.
> >
> > Presumably XQuery expects the Unique Particle Attribute rule,
> > then presumably it just means that the intersection of
> > ambiguous elements in RELAX would have to be used.
> >
> > Cheers
> > Rick Jelliffe
> >
> > -----------------------------------------------------------------
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