Database Design Using the REA Data Model Chapter 17 = chapter 15 in 10e Database Design Using the REA Data Model Copyright © 2012 Pearson Education

Learning Objectives Discuss the steps for designing and implementing a database system. Use the REA data model to design an AIS database. Draw an REA diagram of an AIS database. Read an REA diagram and explain what it reveals about the business activities and policies of the organization being modeled. Copyright © 2012 Pearson Education

Database Design Process System Analysis Conceptual Design Physical Design Implementation & Conversion Operation & Maintenance Copyright © 2012 Pearson Education

The System Analysis Process Systems Analysis Initial planning to determine the need for and feasibility of developing a new system Judgments about the proposal’s technological and economic feasibility Identify user information needs Define the scope of the proposed new system Gather information about the expected number of users and transaction volumes to make preliminary decisions about hardware and software requirements Conceptual Design Developing the different schemas for the new system at the conceptual, external, and internal levels Copyright © 2012 Pearson Education

The System Analysis Process (cont’d) Physical Design Translating the internal-level schema into the actual database structures that will be implemented in the new system New applications are developed Implementation and Conversion Includes all the activities associated with transferring data from existing systems to the new database AIS Testing the new system Training employees Maintaining the New System Copyright © 2012 Pearson Education

Data Modeling Process of defining an information system so it represents an organizations requirements Occurs at two stages of the design process: System analysis Conceptual design Data models: Data flow diagrams (Chapter 3) Flow charts (Chapter 3) Entity-relationship diagrams (Chapter 17) Copyright © 2012 Pearson Education

Entity-Relationship Diagrams Used to graphically represent a database schema Depicts entities Anything an organization wants to collect information about Relationships between entities Copyright © 2012 Pearson Education

E-R Diagram Variations Copyright © 2012 Pearson Education

Resources-Events-Agents Diagram Developed for designing AIS Categorizing entities into: Resources Things that have economic value Events Business activities Management wants to manage and control Agents People and organizations that participate in events Copyright © 2012 Pearson Education

REA Diagram Rules Each event is linked to at least one resource that it affects. Each event is linked to at least one other event. Types of links (relationships): Get events Give events Participation events Each event is linked to at least two participating agents. Copyright © 2012 Pearson Education

Business Cycle Give–Get Relationships Copyright © 2012 Pearson Education

Revenue Cycle REA Diagram Copyright © 2012 Pearson Education

Developing an REA Diagram Identify the events about which management wants to collect information. Identify the resources affected by each event and the agents who participate in those events. What economic resource is reduced by the “Give” event? What economic resource is acquired by the “Get” event? What economic resource is affected by a commitment event? Determine the cardinalities of each relationship. Copyright © 2012 Pearson Education

Cardinalities Describe the nature of relationships between entities How many instances of one entity can be linked to each specific instance of another entity Minimum can be: 0 or 1 Maximum can be: 1 or Many Copyright © 2012 Pearson Education

Three Types of Relationships Relationship type is based on maximum cardinality: One-to-One: One-to-Many: Many-to-Many: Copyright © 2012 Pearson Education