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Re: defaulting

From: Henry S. Thompson <ht@inf.ed.ac.uk>
Date: Fri, 22 Jun 2007 20:23:32 +0100
To: Jeni Tennison <jeni@jenitennison.com>
Cc: public-xml-processing-model-wg@w3.org
Message-ID: <f5bzm2roksr.fsf@hildegard.inf.ed.ac.uk>

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Jeni Tennison writes:

> Richard & Henry wrote:
>> Further to discussion during yesterday's telcon, herewith a proposal
>> about input and output defaulting for pipelines.
>
> I like this. Just one thing:
>
>>   The default input of a step is bound to the default readable port if
>>   it is not otherwise bound;
>>   Non-default inputs are only bound to the default readable port if
>>   you call for that to happen by writing
>>    <p:input port="not-the-default-input-port"/>
>
> The other option would be to say that all inputs are bound to the
> default readable port if they're not explicitly bound, such that
>
> <p:pipeline>
>   <p:xslt1 />
> </p:pipeline>
>
> accepts an XSLT stylesheet input and runs it on itself (this is
> actually something I do quite a lot).
>
> It would make the defaulting story slightly easier to specify, since
> an omitted input would *always* be equivalent to an empty <p:input>
> element for that port.
>
> Is there any reason not to do that?

Yes.  Consider

 <p:pipeline>
  <p:validate-xml-schema/>
 <p:pipeline>

I want that to validate based on what it finds in the document, not
try to use it as a schema to validate itself.

I don't think I'm just being selfish in saying that I suspect that's
likely to be a more common case than yours. . .

> Also, I'm assuming that the default readable port after a given step
> would be the default output of the previous step (in document order)?

Yes, that's already true.

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 Friday, 22 June 2007 19:23:38 GMT

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