In relational databases, many-to-many relationships are modeled using a “middle” table (also known as an “intersection” table). Assume we have two tables named A and B, and they have a many-to-many relationship. A third or “middle” table named AB has a many-to-1 relationship with both A and B.
A many-to-many Association between two Entities in the Vocabulary can be mapped to such a middle table. Therefore, table AB does not need to correspond to a specific Entity in the Vocabulary. However, should the middle table contain additional business fields, then it must have a corresponding Entity in the Vocabulary. In such a situation, attempting to create a new record/row in table AB using rules may run into limitations depending on:
the cardinalities of the associations between AB and A, and AB and B
the identity strategy used for A, B, and AB.
The table below highlights known limitations for combinations of entity identity (Application or Datastore) and association directionality (bidirectional or unidirectional):
* If com.corticon.reactor.engine.NoSyncAssoc property value is true, the order in which the association role assignments appear in the .new[…] operator may result in a situation where things appear to work but, in fact, the middle table is not updated properly in the database. This configuration should be avoided if Application Identity is used.
the cardinalities of the associations between AB and A, and AB and B