Collection Type Constructors in Entity-Relationship Modeling
Sven Hartmann, Sebastian Link · 2015
Abstract. Collections play an important part in everyday life. There-fore, conceptual data models should support collection types to make data modeling as natural as possible for its users. Based on the funda-mental properties of endorsing order and multiplicity of its elements we introduce the collection types of rankings, lists, sets and bags into the framework of Entity-Relationship modeling. This provides users with easy-to-use constructors that naturally model different kinds of collec-tions. Moreover, we propose a transformation of extended ER schemata into relational database schemata. The transformation is intuitive and invertable introducing surrogate attributes that preserve the semantics of the collection. Furthermore, it is a proper extension to previous trans-formations, and results in a relational database schema that is in Inclu-sion Dependency Normal Form. In addition, we introduce a uniqueness constraint that identifies collections uniquely and guarantees referential integrity at the same time. 1