Proposal: (node ...) construction rule type

Subject: Proposal: (node ...) construction rule type
From: David Megginson <ak117@xxxxxxxxxxxxxxxxxxx>
Date: Thu, 14 Aug 1997 12:55:46 -0400
Paul Prescod writes:

 > People have been asking about processing instructions. I also would like
 > to be able to catch individual characters, either to surpress them or to
 > transform them. The same holds for (external-data ...) nodes. What would
 > people think about a new kind of construction rule, unbundled from the
 > query feature:
 > (node class ...)
 > Eg:
 > (node processing-instruction (...))
 > (node external-data (...))
 > (node char (empty-sosofo))

What a great idea!  It would provide an elegant primitive for the
existing construction rules -- I'd guess that they could all be
implemented in terms of it (in some cases, with the addition of 'if'
statements and the 'next-match' procedure).  Would anyone care to try?
(Hint: don't forget the priority expressions.)

 > The first two need not slow down processing in a style-sheet at all. The
 > last might be a common form that could be optimized for.

The problem is that there is no mechanism in DSSSL for adding
construction rules, the way that there is for adding flow-object
classes and external procedures.  If James modifies Jade to include
the 'node' construction rule, I suspect that his program will no
longer be DSSSL-compliant (at least, until the standard changes).
Then again, he could provide a command-line option to disable the
extension for full DSSSL compliance.

I cannot imagine that it would take me more than two days to make and
test the change in Jade, so using my normal conversion, it would take
James about two hours.

All the best,


David Megginson                 ak117@xxxxxxxxxxxxxxxxxxx
Microstar Software Ltd.         dmeggins@xxxxxxxxxxxxx

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