Re: combine proposal

[James Clark <jjc@thaiopensource.com>]

> > 2. Restrict combine="group" to cases where the order of the patterns
being
> > combined is irrelevant (eg two <attribute> patterns).
>
> I think the function "allowsChildren" is difficult to implement although
> possible to implement.

Good point.  This is a bit tricky.  I guess I would internally use another
kind of pattern orderIndependentGroup, which inherits from group, and then
check the order-independence constraint later on, at the same time as
checking the constraint on the use of <data>.

Maybe there's an easy solution to this.  Observe that in all cases where
combine="group" is allowed by this proposal, it has exactly the same
semantics as combine="interleave".  So we could save ourselves a bunch of
complexity in the spec and in implementations without forgoing any
functionality just by getting rid of combine="group" altogether.

James