[Bug 5063] Inheritance of some SML reference constraints


------- Comment #3 from sandygao@ca.ibm.com  2007-11-05 19:50 -------
I don't think our resolution to bug 4643 can be directly applied here. The
reason we believe 4643 should be resolved by allowing inheritance is that
schema already inherits types from substitution group (and we thought it should
have inherited more). But this one is different. Schema doesn't inherit
anything in particle restriction.

For substitution group, because it's very clear what the inheritance source is,
it's easier for people to imagine what's expected. For particle restriction,
it's not always as clear, when content models become complex. Having this kind
of side-effect may sometimes causes surprises.

This also makes it hard (if not impossible) to achieve the same result if a
processor chooses to support schema 1.1, where the "matching particle in the
base" concept no longer exists (it's possible for the same particle in the
derived type to have multiple counterparts in the base).

If we really want this kind of inheritance (and I'm not convinced), we could
look at how schema 1.1 handles Type Alternative Table inheritance. They seem to
be very similar issues and demand the same kind of solutions.

Received on Monday, 5 November 2007 19:50:12 UTC