Database Reference
In-Depth Information
CHAPTER 7
ENTITY-RELATIONSHIP DATA MODEL
CHAPTER OBJECTIVES
•
Study entity-relationship (E-R) data modeling as another technique to create
a semantic model
•
Understand the principles and concepts of E-R modeling
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Discuss the components of the E-R data model
•
Explore special types of business entities and relationships
•
Examine an entity-relationship diagram
Database practitioners and experts refer to a data model that captures the true
meaning of real-world information requirements as a semantic data model. Such a
model truly represents the semantics or real meaning and implications of what you
need to model from the relevant real-world information. We have studied the
object-based data modeling technique as a technique for creating a semantic data
model. Now we want to study another popular technique for building a semantic
data model: entity-relationship (E-R) data modeling.
As you review the concepts, principles, and components of the E-R data model,
you will notice a number of similarities with the object-based data model. Both
achieve the same purpose; both are intended to produce similar results; both reflect
the true meaning of information requirements. As we proceed with our discus-
sion, wherever essential, we will compare the two techniques and point out the
correspondences.
Because of the similarities, we need not go over again the basic principles and
examples of the mapping of real-world information to the components of the model.
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