17 database design using the rea data model
TRANSCRIPT
Chapter 17Database Design Using the REA Data Model
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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.
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Database Design Process
System Analysis
Conceptual Design
Physical Design
Implementation & Conversion
Operation & Maintenance
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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
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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
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)
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Entity-Relationship Diagrams
Used to graphically represent a database schema
Depicts entities Anything an organization wants to collect information
about
Relationships between entities
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E-R Diagram Variations
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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
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REA Diagram Rules
1. Each event is linked to at least one resource that it affects.
2. Each event is linked to at least one other event. Types of links (relationships):
Get events Give events Participation events
3. Each event is linked to at least two participating agents.
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Business Cycle Give–Get Relationships
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Revenue Cycle REA Diagram
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Developing an REA Diagram
1. Identify the events about which management wants to collect information.
2. 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?
3. Determine the cardinalities of each relationship.
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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
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Three Types of Relationships
Relationship type is based on maximum cardinality: One-to-One:
One-to-Many:
Many-to-Many:
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