Re: The XSL-List Digest V1 #149

> The various rules in a stylesheet should be able to be in any order
> without having the order affect which rule is used in what case
>(except perhaps as a final arbiter in an "error recovery" situation).

This requires a most-specific-matching-rule system, as opposed to the "lazy
evaluation" technique of first-matching-rule. Which in turn is going to
require a very tightly nailed down explanation of how that distance is
calculated.

A problem arises when two rules wind up being the same distance from the
node being evaluated (eg, matching on different attributes). This requires
some disambiguation mechanism. In other rulesystems I've used, this has
usually been handled by some form of first-best-match or last-best-match.
If you're going to declare that position will not be meaningful, I think
you're going to need something else to break those ties consistantly. This
might be expressed as a "rule priority number".

Workable. But I'm not sure whether it improves convenience more than it
obscures intent or vice versa. Ordering is arguably easier for humans to
visualize, and keep track of, than priority numbers would be.

______________________________________
Joe Kesselman  / IBM Research
Unless stated otherwise, all opinions are solely those of the author.



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