Implementing a Design

In this chapter we describe two techniques. In section 7.2 we show how to construct an Entity Relationship representation given a set of 3NF relations. In section 7.3 we look at the converse process, that is producing a relational representation of an Entity Relationship model. The first technique is optional: it does not add any new information to an existing E-R model. Indeed some of the semantics of the E-R model (optionality, sub-typing) cannot be captured by this process. Nevertheless because Normalisation is independent of E-R modelling, converting a 3NF relation to an E-R representation is a means of checking our independently constructed E-R model.