[Bug 5293] Subsumption

http://www.w3.org/Bugs/Public/show_bug.cgi?id=5293





------- Comment #6 from mike@saxonica.com  2007-11-30 10:45 -------
A further example here: consider the two types

B: ab?|ba?

D: a?&b? [count(*)>0]

where the square brackets indicate an assertion.

These two types are equivalent (both allow the instances a, b, ab, or ba), and
as far as I can see our current rules require processors to treat D as a valid
restriction of B. But I don't think this can be done without some sophisticated
theorem proving (we know they're equivalent because we can enumerate the
instances, but that clearly isn't a viable strategy in the general case.)

The problem is exacerbated by the fact that all the complexity arises in cases
like this that will very rarely arise outwith conformance tests.

Received on Friday, 30 November 2007 10:45:14 UTC