Re: xpath processing brain dead

On Mon, 2009-03-02 at 07:54 -0500, Andrew Dunstan wrote:
> 
> Simon Riggs wrote:
> > On Sun, 2009-03-01 at 18:22 -0500, Andrew Dunstan wrote:
> >
> >   
> >> I think the XML type needs to conform to the SQL/XML spec. However, we
> >> are trying to apply XPath, which has a different data model, to that 
> >> type - hence the impedance mismatch.
> >>
> >> I think that the best we can do (for 8.4, having fixed 8.3 as best we 
> >> can without adversely changing behaviour) is to throw the
> >> responsibility 
> >> for ensuring that the XML passed to the function is an XML document
> >> back on the programmer. Anything else, especially any mangling of the
> >> XPath 
> >> expression, presents a very real danger of breaking on correct input.
> >>     
> >
> > Can we provide a single function to bridge the gap between fragment and
> > document? It will be clearer to do this than to see various forms of
> > appending/munging, even if that function is a simple wrapper around an
> > append.
> >
> >   
> 
> I have no objection to providing an *extra* function that explicitly 
> wraps non-documents and prefixes the xpath expression in that case, and 
> is documented to have limitations. But I don't think we can provide a 
> single function that always "does the right thing", especially when that 
> is so ill-defined in the case of fragments.

Is it just that in you _can't_ use Xpath on fragments, and you _need_ to
pass full documents to Xpath ? 

At least this is my reading of Xpath standard.

> cheers
> 
> andrew
-- 
Hannu Krosing   http://www.2ndQuadrant.com
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