Containment navigation properties define entity sets, and keyless abstract entity types cannot be used as the type of an entity set, which includes Edm.EntityType. That's rather hard to deduce from the current spec, so spell it out in section 4.5
Containment navigation properties define entity sets, and keyless abstract entity types cannot be used as the type of an entity set, which includes Edm.EntityType. That's rather hard to deduce from the current spec, so spell it out in section 4.5