The Enhance E-R Model
Chapter 4 The Enhanced E-R Model and Business Rules
Chapter Objectives
The purpose of this chapter is to present some important extensions to the E-R model (described in Chapter 3) that are useful in capturing additional business meaning. In particular we describe two types of extensions to the E-R model. The enhanced entity-relationship (EER) model includes constructs for supertype/subtype relationships. The inclusion of new notation for business rules allows the designer to capture a broader range of constraints on the data model than were previously available. Specific student objectives are included in the beginning of the chapter. From an instructor’s point of view, the objectives of this chapter are to:
1. Introduce the concept of supertype/subtype relationships, and prepare the student to recognize when to use these relationships in data modeling.
2. Describe the use of specialization (top-down perspective) and generalization (bottom-up perspective) as complementary techniques for defining supertype/subtype relationships.
3. Introduce notation for specifying both completeness constraints and disjointness constraints when modeling supertype/subtype relationships.
4. Help students gain sufficient perspective so that they recognize when to use (and when not to use) supertype/subtype relationships in realistic business situations.
5. Describe the basic premises of a business rules paradigm.
6. Describe a simple framework for categorizing business rules.
7. Introduce notation for modeling typical operational constraints that can be incorporated in your EER diagram.
Classroom Ideas
1. Introduce the concept of supertypes and subtypes with a familiar example, such as VEHICLE (subtypes are CAR, TRUCK, SUV, etc.).
2. Introduce the basic notation for supertype/subtype relationships (Figure 4-1). Use this notation to represent the example you introduced in (1).
3. Discuss the EMPLOYEE example with subtypes (Figure 4-2). Use
Chapter Objectives
The purpose of this chapter is to present some important extensions to the E-R model (described in Chapter 3) that are useful in capturing additional business meaning. In particular we describe two types of extensions to the E-R model. The enhanced entity-relationship (EER) model includes constructs for supertype/subtype relationships. The inclusion of new notation for business rules allows the designer to capture a broader range of constraints on the data model than were previously available. Specific student objectives are included in the beginning of the chapter. From an instructor’s point of view, the objectives of this chapter are to:
1. Introduce the concept of supertype/subtype relationships, and prepare the student to recognize when to use these relationships in data modeling.
2. Describe the use of specialization (top-down perspective) and generalization (bottom-up perspective) as complementary techniques for defining supertype/subtype relationships.
3. Introduce notation for specifying both completeness constraints and disjointness constraints when modeling supertype/subtype relationships.
4. Help students gain sufficient perspective so that they recognize when to use (and when not to use) supertype/subtype relationships in realistic business situations.
5. Describe the basic premises of a business rules paradigm.
6. Describe a simple framework for categorizing business rules.
7. Introduce notation for modeling typical operational constraints that can be incorporated in your EER diagram.
Classroom Ideas
1. Introduce the concept of supertypes and subtypes with a familiar example, such as VEHICLE (subtypes are CAR, TRUCK, SUV, etc.).
2. Introduce the basic notation for supertype/subtype relationships (Figure 4-1). Use this notation to represent the example you introduced in (1).
3. Discuss the EMPLOYEE example with subtypes (Figure 4-2). Use