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Data Modeling

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2. The Entity-Relationship Model

2. The Entity-Relationship Model
This section’s goal: After completing this chapter, you should be able to explain the three phases of database design,
Why are multiple phases useful?

evaluate the significance of the Entity-Relationship Model (ER model) for DB design, enumerate the basic constructs of the ER model, develop ER diagrams (schemas in the ER model) for a given application, translate ER models into equivalent (as far as possible) relational models.
Marc H. Scholl (DBIS, Uni KN) Information Management Winter 2007/08 48

2. The Entity-Relationship Model

Introduction

Database design (1)

Overall goal of DBMS usage: Efficiently develop programs to support given real-world tasks. These programs need to store data persistently. To develop these programs, apply proven methods of software engineering—specialized to support data-intensive programs. Definition (Database Design) Database Design is the process of developing a database schema for a given application. DB design is a subtask of the overall software engineering effort.

Marc H. Scholl (DBIS, Uni KN)

Information Management

Winter 2007/08

49

2. The Entity-Relationship Model

Introduction

Database design (2)

The specification of programs and data is intertwined: The schema should contain the data needed by the programs. Programs are often easy to develop once the structure of the data to be manipulated has been specified. Data, however, is an independent resource: Typically, additional programs will be developed later based on the collected data. Also, ad-hoc queries will be posed against the DB.

Marc H. Scholl (DBIS, Uni KN)

Information Management

Winter 2007/08

50

2. The Entity-Relationship Model

Introduction

Database design (3)

During DB design, a formal model of the relevant aspects of the real world (“mini

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