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Variable and option binding proposal

From: Henry S. Thompson <ht@inf.ed.ac.uk>
Date: Tue, 25 Mar 2008 14:13:31 +0000
To: public-xml-processing-model-wg@w3.org
Message-ID: <f5b8x06evsk.fsf@hildegard.inf.ed.ac.uk>

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As promised, a proposal for specifying how options and variables get
bound [1].  I've done a fair amount of low-level rework to make the
sub-sections about vars/opts/params consistent, but the major work is
to tell the binding story in detail.

1) Syntax.  I think given the constraint on bindings for variables (no
   pipes from sibling steps), we would do best to restrict variables
   to the beginning of subpipelines.  I think we can do that in the
   minimal way, by changing the _subpipeline_ pseudo-content-model to
   be:

 p:variable*,
  (p:for-each|p:viewport|p:choose|p:group|p:try|
   p:standard-step|pfx:user-pipeline |p:documentation|p:pipeinfo)*

2) Environment.  We need to put bindings back into the environment, see
   2.5 [2] in the new alternate draft.

3) Existing references to 'in-scope options' etc. need to be changed
   to reference the in-scope bindings.  For example, in both XPath1
   and XPath2 versions of the Processor XPath context (section 2.6.1),
   the In-scope variables/Variable values entry should read "The
   in-scope bindings from the environment of the step."

4) Slight modifications to 2.7 Variables:

   'Variales' -> 'Variables'

   "Pipeline authors can create variables to hold computed values."
    -->
   "Pipeline authors can create variables to hold computed values
    using _p:variable_."

5) Slight modification to 4.7:

   "standards steps" --> "standard steps"

6) Rework of 5.7.1 et seq. _p:variable_ and friends, see 5.7.1--5.7.4
   [3] in the new alternate draft.

7) Minor changes of 5.7.5 Namespaces on variables etc., to sync with
   the other changes to 5.7
   
ht

[1] http://www.w3.org/XML/XProc/docs/alternate/Overview.html
[2] http://www.w3.org/XML/XProc/docs/alternate/Overview.html#environment
[3] http://www.w3.org/XML/XProc/docs/alternate/Overview.html#variables-options-parameters
- -- 
 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/
[mail really from me _always_ has this .sig -- mail without it is forged spam]
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Received on Tuesday, 25 March 2008 14:14:04 GMT

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