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Re: p:choose is poorly and/or incorrectly specified

From: Henry S. Thompson <ht@inf.ed.ac.uk>
Date: Tue, 21 Apr 2009 10:12:40 +0100
To: Toman_Vojtech@emc.com
Cc: <public-xml-processing-model-comments@w3.org>
Message-ID: <f5bzlea9xpz.fsf@hildegard.inf.ed.ac.uk>
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Toman_Vojtech writes:

> If we add a primary output port to p:error, we will have to decide
> whether it produces sequences (possible problems with other subpipelines
> whose outputs *don't* produce sequences), or not (possible problems ith
> other subpipelines whose outputs *do* produce sequences).

Yeah, I thought about that but didn't say anything, because it
depressed me :-(

I wonder if we should reconsider the exact nature of the constraint on
outputs across subpipelines in choose and try.  Since we allow
sequence-out->single-in connections, couldn't we allow both
sequence-out and single-out in choose/try subpipes, with the implicit
casting of the single-outs to sequence-out iff any branch has an
explicit sequence-out?

As far as I can see this would not change the behaviour of any
currently-allowed pipeline, and it would, together with making the
primary output of p:error a sequence-out port (always 0-length), would
solve the problem.

Surely the 90% case for p:error will be in a branch of a choose or
try, so it is worth fixing this. . .

ht
- -- 
       Henry S. Thompson, School of Informatics, University of Edinburgh
                         Half-time member of W3C Team
      10 Crichton Street, Edinburgh EH8 9AB, SCOTLAND -- (44) 131 650-4440
                Fax: (44) 131 651-1426, e-mail: ht@inf.ed.ac.uk
                       URL: http://www.ltg.ed.ac.uk/~ht/
[mail really from me _always_ has this .sig -- mail without it is forged spam]
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Received on Tuesday, 21 April 2009 09:13:27 GMT

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