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Objection to XProc: An XML Pipeline Language section(s) 5.7.3, 5.7.4

From: David A. Lee <dlee@calldei.com>
Date: Mon, 8 Dec 2008 08:39:58 -0500
Message-ID: <F15CE08DBDCD4EEF9776C2F0FEF3ACAF@calldei.com>
To: <public-xml-processing-model-comments@w3.org>
I would like to formally object to the following sections of the XProc: An XML Pipeline Language specification,
W3C Candidate Recommendation 26 November 2008

Sec 5.7.3 p:with-option
Sec 5.7.4 p:with-param

The objection is to the default binding of the context for the select= attributes,
which in these sections are defined to be the default readable port.
I propose that the default binding should be <p:empty/> unless explicitly bound.

A summary of my objection is that in my opinion, as a implementer of the xproc standard,
that this prevents a conforming xproc implementation from potentially streaming through 
any action that uses any parameters or options specified with p:with-option and p:with-param
because the processor would have to collect (fork and buffer) the input for use by the select
attribute prior to starting the action, even if the xpath expression did not reference any context.
In my opinion, the advantage to the user for this convenience is far outweighed by the cost
to the implementation.  In fact the current test suites do not have a single case where the context
is actually used.   By coding this into the specs it is placing an extreme burden onto future implementations
and onto the potential performance of any future implementations, with , in my opinion, little or no value to 
xproc pipeline authors.  

In my implementation of xproc I intend on not implementing this portion of the spec due to these concerns.

Note there was an alternative suggested for implementers, which is performing full static analysis of the xpath option
to determine if a context is referenced.    I suggest this is an undue amount of effort required for implementers of this 
specification, considering a goal of the spec is to allow implementations to reuse existing standard libraries which do 
not have this capability. A simple change to the spec would eliminate this burden while not having a significant
impact on usefulness to pipeline authors.

Please refer to threaded discussions in the XProc mailing list


Thank You.
David A. Lee, 
President DEI Services Inc.

David A. Lee
Senior member of the technical staff
Epocrates, Inc.

David A. Lee
Nexstra, Inc.
Received on Monday, 8 December 2008 13:40:34 UTC

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