10.8. Summary
Join constraints apply to roles projected from an ORM path that involves at least one conceptual join. The simplest kind of join constraint applies to a single join path. External uniqueness constraints are of this kind. Join subset constraints are subset constraints between two role sequences, where at least one of the role sequences is projected from a join path. Join equality constraints and join exclusion constraints also include at least one role sequence argument projected from a join path.
Conceptual joins may be inner or outer. If there are multiple paths connecting roles in a role projection, role sequence numbers are needed to disambiguate the intended role path.
Alethic rules impose necessities that cannot possibly be ...
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