As a developer I would like a consistent treatment of relationships in EntityType and Core.EntityStore.
Core.EntityStore actually assume that there can be a maximum of one relationship between two entity types (because it can be stored a maximum of onea referenced entity per entity), while the specification of EntityType.getRelation () explicitly provides multiple relationships between two entity types.
EntityStore now supports multiple references beween two entities. Methods
to get and set a related Entity along with a relation name where added..