Chapter 17: Database Design Using the REA Data Model

Chapter 17Database Design Using the REA Data ModelCopyright © 2012 Pearson Education17-1Learning ObjectivesDiscuss 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 Education17-2Database Design ProcessCopyright © 2012 Pearson Education17-3The System Analysis ProcessSystems AnalysisInitial planning to determine the need for and feasibility of developing a new systemJudgments about the proposal’s technological and economic feasibilityIdentify user information needsDefine the scope of the proposed new systemGather information about the expected number of users and transaction volumes to make preliminary decisions about hardware and software requirementsConceptual DesignDeveloping the different schemas for the new system at the conceptual, external, and internal levelsCopyright © 2012 Pearson Education17-4The System Analysis Process (cont’d)Physical DesignTranslating the internal-level schema into the actual database structures that will be implemented in the new systemNew applications are developedImplementation and ConversionIncludes all the activities associated with transferring data from existing systems to the new database AISTesting the new systemTraining employeesMaintaining the New SystemCopyright © 2012 Pearson EducationData ModelingProcess of defining an information system so it represents an organizations requirementsOccurs at two stages of the design process:System analysisConceptual designData models:Data flow diagrams (Chapter 3)Flow charts (Chapter 3)Entity-relationship diagrams (Chapter 17)Copyright © 2012 Pearson Education17-6Entity-Relationship DiagramsUsed to graphically represent a database schemaDepicts entitiesAnything an organization wants to collect information aboutRelationships between entitiesCopyright © 2012 Pearson Education17-7E-R Diagram VariationsCopyright © 2012 Pearson Education17-8Resources-Events-Agents DiagramDeveloped for designing AISCategorizing entities into:ResourcesThings that have economic valueEventsBusiness activitiesManagement wants to manage and controlAgentsPeople and organizations that participate in eventsCopyright © 2012 Pearson Education17-9REA Diagram RulesEach 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 eventsGive eventsParticipation eventsEach event is linked to at least two participating agents.Copyright © 2012 Pearson Education17-10Business Cycle Give–Get RelationshipsCopyright © 2012 Pearson Education17-11Revenue Cycle REA DiagramCopyright © 2012 Pearson Education17-11Developing an REA DiagramIdentify 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 Education17-13CardinalitiesDescribe the nature of relationships between entitiesHow many instances of one entity can be linked to each specific instance of another entityMinimum can be: 0 or 1Maximum can be: 1 or ManyCopyright © 2012 Pearson Education17-14Three Types of RelationshipsRelationship type is based on maximum cardinality:One-to-One:One-to-Many:Many-to-Many:Copyright © 2012 Pearson Education17-15