I am working on a Chen ERD to model our organizations merchandise.  Our central entity is a Style.  We have supplemental entities of Color and Season.  I am defining our assortment as the relationship between these three entities, and this relationship itself will have attributes and is defined by the three entities which participate in the mandatory relationship.  The rules are;Many Styles can be offered in a Season, and a Style can be offered in many Seasons.Within a Season, a Style can be offered in Many Colors.I then have 2 other entities, one of which I believe is a weak entity, Climate, and the other may be weak, but I am not sure, this being Transaction Channel.I am thinking of these as relationships off of a relationship?  Meaning, for a given Style/Color combination offered in a Season, it can be available through 1 or more Transaction Channels.  Additionally, within a season, a given Style/Color combination can be intended for 1 or more Climates.Is it valid to have relationships off of relationships?  Or does this requirement dictate that I should think of this Style/Color/Season relationship as an entity itself, and define the relationships to Climate and Transaction Channel off of this entity?
Relationships in a Chen ERD
database design;relational database;entity;data modeling