8 Further Extensions for ER Diagrams with Binary Relationships
8.1 INTRODUCTION
Having developed the basic entity-relationship (ER) model in Chapters 4 through 7, this chapter deals with some extensions to the basic model. We introduce a new concept—attributes of relationships and present several examples. We then revisit step 6 of the ER design methodology to include attributes of relationships. Next, the chapter looks at how more entities and relationships are added to the ER model and how attributes and relationships evolve into entities, all the while refining our ER design methodology. Relationships may develop into entities, creating an intersection entity. The grammar and structured English for the ...
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