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Re: Errors in definition of XPath static context

From: Norman Walsh <ndw@nwalsh.com>
Date: Wed, 19 Nov 2008 09:31:05 -0500
To: public-xml-processing-model-comments@w3.org
Message-ID: <m2vduj949i.fsf@nwalsh.com>
ht@inf.ed.ac.uk (Henry S. Thompson) writes:
> Why isn't the analogy, then, that for XProc the static context is
> determined by the pipeline document context, and the dynamic context
> the relevant input document?  If so, then what we have today is pretty
> much correct, and your proposal is not needed.

Yes. Looking more closely, I think you're right.

> The only thing I see
> that needs to change is namespaces, which needs to be
> split:
>   staticly known: from the containing element
>   [oops -- Houston, we have a problem]: from p:namespaces
> The split doesn't work, does it?  We are going to end up saying that
> the static context isn't really static, because it has to be computed
> at the same time that constructed XPaths are constructed. . .

Right. Since p:namespace can refer to the source document, I think we do
have to fix that one:

In the static context:

Known namespaces:

   The namespace declarations in-scope for the containing element.

And in the dynamic context:

Known namespaces:

   The namespace declarations in-scope for the containing element or
   made available through p:namespaces.

It happens that we don't have any constructs that can access the
statically known namespaces except dynamically, so the split hardly

> In which case, the current document is entirely correct, as far as I
> can see.  The properties you list don't _occur_ in the dynamic
> context, after all.

All of the properties in the static context also appear in the dynamic 
context. From XPath 2.0, 2.1.2 Dynamic Context, paragraph 3:

  The dynamic context consists of all the components of the static
  context, and the additional components listed below.

> Sigh.  We probably should talk about this tomorrow on the call.

I suppose, though I think the problem's much smaller than I imagined.

                                        Be seeing you,

Norman Walsh <ndw@nwalsh.com> | The way to get things done is not to
http://nwalsh.com/            | mind who gets the credit of doing
                              | them.--Benjamin Jowett

Received on Wednesday, 19 November 2008 14:31:45 UTC

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