[relax-ng] Implementation of restrictions on interleave (2)

In the last conference call, I've got an action item to implement
proposed restrictions on <interleave>.


I've already implemented the restriction of <element> in <interleave>,
<data>/<text> in <interleave>, so what I did this time is to expand it
to support <value> in <interleave>. Therefore it was relatively simple.
It just took 45 minutes including a brief test.

Checking (a) value in interleave, (b) attribute in group/interleave and
(c) element in interleave can be done by a very similar algorithm. So if
you got an idea about implementing one, implementing all is just a
matter of time. It would be even easier for languages like C++ where one
can use templates.



As James Clark pointed out, I agree that it is easier and natural to
implement "text in interleave" check as a part of checking 7.2 (string
sequences). Maybe we should move this restriction from 7.4 to 7.2

I also felt that a note that says "bullets from the third to the fifth
will only apply to <interleave> in <list>, because other cases are
prohibited by the section 7.2" might help.



As of the writing, it occurred to me that it is probably possible to
perform checks of 7.2 and 7.4 at the same time, thereby reducing the
time to check those constraints.


regards,
--
Kohsuke KAWAGUCHI                          +1 650 786 0721
Sun Microsystems