6 Extending Relationships/Structural Constraints
6.1 INTRODUCTION
In Chapters 4 and 5, we introduced some components of entity-relationship (ER) diagrams: entities, attributes, and relationships. It is insufficient for requirement elicitation to define relationships without also defining structural constraints—information about how two (or more) entities are related to one another. There are two types of structural constraints: cardinality and participation.
In this chapter, in addition to the structural constraints of relationships, we introduce a grammar to describe what we have drawn. The grammar will help with the requirement elicitation process as we will specify a template for the English that can ...
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