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Re: Deleting in a viewport

From: Jeni Tennison <jeni@jenitennison.com>
Date: Fri, 10 Nov 2006 13:53:47 +0000
Message-ID: <4554846B.1050208@jenitennison.com>
To: public-xml-processing-model-wg@w3.org

Hi,

Alex Milowski wrote:
> Norman Walsh wrote:
>> / Alex Milowski <alex@milowski.org> was heard to say:
>> | I'm not certain we have a good way to do this because a viewport
>> | always requires an output for the replacement.
>> |
>> | Any ideas how we might solve this?
>>
>> With an p:empty component that takes no inputs and returns an empty
>> document sequence?
> 
> I thought about that... but we don't say how empty sequences are
> handled.
> 
> I suppose we could say that a viewport's replacement must either
> be a singleton sequence or an empty sequence.  An empty sequence
> has the effect of deleting the matching subtree.

I was assuming that we'd allow an empty <p:output> if we wanted the 
output to be bound to an empty sequence. Note that this is required 
within <p:when>/<p:otherwise> as well, for situations where the 
<p:choose> is effectively splitting a sequence of documents onto two 
output ports.

  <p:choose step="previous" source="result">
    <p:when test="/foo">
      <p:output port="foos" step="previous" source="result" />
      <p:output port="bars" />
    </p:when>
    <p:otherwise>
      <p:output port="foos" />
      <p:output port="bars" step="previous" source="result" />
    </p:otherwise>
  </p:choose>

I was also assuming that a viewport's replacement could be a sequence of 
documents, in which case the original element is replaced by the 
concatenation of that sequence. This makes it easy to use viewport to 
insert elements into a document.

I agree with Henry that we need a 'delete' built-in component as well.

Cheers,

Jeni
-- 
Jeni Tennison
http://www.jenitennison.com
Received on Friday, 10 November 2006 13:54:00 GMT

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