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Re: I'm _still_ confused about 3.8 Extension elements

From: Henry S. Thompson <ht@inf.ed.ac.uk>
Date: Wed, 09 Jan 2008 11:18:00 +0000
To: Norman Walsh <ndw@nwalsh.com>
Cc: public-xml-processing-model-comments@w3.org
Message-ID: <f5bfxx7xn6f.fsf@hildegard.inf.ed.ac.uk>

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Norman Walsh writes:

> |  "An element is only an extension element if it is an ignorable
> |   element that occurs as a direct child of a p:pipeline or
> |   p:pipeline-library."
> |
> |  "[E]lements in a subpipeline are interpreted as follows. . .
> |    2. Is in ignorable namespace?
> |     a. Is a known extension? Process as appropriate."
> |
> | How can an element in a sub-pipeline be a direct child of p:pipeline?
>
> Well, all of the elements in the subpipeline are direct children of
> p:pipeline, no?

Um, yes, but it seems very odd for extension elements to be allowed
directly inside p:pipeline/p:declare-step, but not inside
e.g. p:group. . .

> | Looking at the RNG schema, and other parts of the spec., I _think_ the
> | editor's intent was to allow extensions only in subpipelines, as a way
>
> Well, in fact, only in the subpipeline of a p:pipeline. That needs to
> be expanded to include p:declare-step now too.

But _why_ only there?  I've lost whatever memory of the motivation for
this restriction there might have been.

> | of allowing for . . . extensions.  But that is completely at odds with
> | the following from the beginning of 3.8:
> |
> |  "The presence of an extension element must not cause the connections
> |   between steps to differ from the connections that any other
> |   conformant XProc processor would produce."
> |
> | Such a constraint would render any extension useless, as far as I can
> | tell.
>
> That's not the intent. The intent was to provide a modicum of
> interoperability if the processor doesn't recognize the extension.
>
> Extensions shouldn't interfer with the static analysis, IMHO.

I'm still lost -- can you give an example?

ht
- -- 
 Henry S. Thompson, HCRC Language Technology Group, University of Edinburgh
                     Half-time member of W3C Team
    2 Buccleuch Place, Edinburgh EH8 9LW, SCOTLAND -- (44) 131 650-4440
            Fax: (44) 131 650-4587, e-mail: ht@inf.ed.ac.uk
                   URL: http://www.ltg.ed.ac.uk/~ht/
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Received on Wednesday, 9 January 2008 11:18:10 GMT

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