The ORM Foundation

May a value constraint span multiple roles in ORM?  Examples in the "Big Brown Book" seem to cover only one role.  Consider the below example.  If the example constraint is invalid, might an alternative be to objectify the spanned roles and then apply a value constraint to the objectified type?

Best,
Matt 

 Currently, role value constraints apply only to single roles. Objectification can be a solution in some cases, but is not advisable in your example since there is no uniqueness constraint over the (A,B) role pair.

If you have a real world example where you wish to apply a value constraint matching the pattern you show, please provide it and we will consider whether to extend our value constraint support for such cases. 

Cheers

Terry