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Re: Implicit and explicit input bindings

From: Henry S. Thompson <ht@inf.ed.ac.uk>
Date: Wed, 11 Jul 2007 17:18:22 +0100
To: Norman Walsh <ndw@nwalsh.com>
Cc: public-xml-processing-model-wg@w3.org
Message-ID: <f5bejjevrqp.fsf@hildegard.inf.ed.ac.uk>

Hash: SHA1

Norman Walsh writes:

> Are the following pipelines logically the same? Are they all legal?
>   <p:pipeline name="explicit">
>     <p:input port="source" primary="yes"/>
>     <p:output port="result" primary="yes"/>
>     <p:identity>
>       <p:input port="source">
>         <p:port step="explicit" port="source"/>
>       </p:input>
>     </p:identity>
>   </p:input>
>   <p:pipeline name="semi-implicit">
>     <p:input port="source" primary="yes"/>
>     <p:output port="result" primary="yes"/>
>     <p:identity>
>       <p:input port="source"/>
>     </p:identity>
>   </p:input>
>   <p:pipeline name="fully-implicit">
>     <p:input port="source" primary="yes"/>
>     <p:output port="result" primary="yes"/>
>     <p:identity/>
>   </p:input>

With that trivial correction, all the same.

> Several times now, I've gotten the impression that some people feel
> that
>   <px:step-name>
>     <p:input name="foo"/>
>   </px:step>
> is semantically different from
>   <px:step-name/>
> and I don't think it should be. If you think it is, please explain how
> and why.

If px:step-name has no primary input ports, then in the first of those
the default readable port will be connected to the 'foo' port, but in
the second nothing will be bound to any of the step's input ports.

Now since we've agreed that unconnected input ports are always static
errors, the value here is modest -- it amounts to saying that you
_must_ always write something to cause a connection to a non-primary
input port.

- -- 
 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, 11 July 2007 16:18:38 GMT

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