Resolve a Many-to-Many Relationship in a Logical Model

To avoid design problems that can be caused by many-to-many relationships, you can resolve a many-to-many relationship by adding associative entities to act as links for two ambiguously related entities. If you insert an associative entity between the two entities involved in a many-to-many relationship, you can change the relationship into a series of one-to-many relationships and use the new relationships to clarify how the data model works.

To resolve a many-to-many relationship, right-click the relationship to resolve and click Create Association Entity. Follow the instructions in the Many-To-Many Transformation Wizard to transform the many-to-many relationship into an association entity.

More information:

Resolve a Many-to-Many Relationship with a Transformation