15 - Chapter 15 Database Design Using the REA Data Model...

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Unformatted text preview: Chapter 15 Database Design Using the REA Data Model Data Learning Objectives Learning Describe the REA model for designing a Describe database database Use the REA model to build an Access Use database database REA Data Model REA Resources, Events, Agents esources, vents, Provides guidance for database design by • • Identifying what entities should be included How to structure relationships among entities REA Data Model Definitions REA Resources are things that have economic value Examples: cash, land, equipment Events are the activities of the business Examples: sales, purchases, cash receipt, cash disbursement Agents are the people and organizations that Agents participate in the business activities participate Examples: customers, suppliers, employees REA Data Model Definitions REA Economic exchanges are the value chain activities Economic that directly affect the quantity of resources that Examples: sales, cash collection, cash disbursement Commitments represent promises to engage in future Commitments economic exchanges economic Examples: orders placed by customers, orders placed with vendors REA Data Model REA Each event is linked to a resource Events that change the quantity of a resource are Events linked to the resource by a stockflow relationship linked Events that represent future commitments are linked Events to the resource by reserve relationships to Each event is linked to two agents Each economic exchange event is linked with another Each economic exchange event in a give-to-get duality relationship relationship REA Data Modeling Steps REA Identify economic exchange events that represent give-to-get Identify duality relationships duality Identify the resources affected by each economic exchange Identify event event Identify the agents who participate in each economic exchange Identify event event Analyze each economic exchange event to determine if it Analyze should be decomposed into a combination of one or more commitment events and an economic exchange event. Replace if necessary Replace Determine the cardinalities of each event Revenue Cycle REA Diagram Revenue (Batini min max method fig. 15-6) Events InventoryOrders (0,N) Reserve Commitment InventorySales Customer Orders (1,1) (1,1) (0,1) Participant Inventory Leads to (0,N) (0,N) (0,N) Participant (1,1) (1,N) Sales (1,1) Stockflows Economic Exchange (give-to-get duality) (0,N) Sales-Cash Receipts (1,N) Cash Receipts (1,1) Participant Cardinalities (0,N) (0,N) Participant Customer Salesperson Each event linked w/ two agents Participant (0,N) Resources Agents Customer (1,N) (0,1) Cash (0,N) Stockflow (1,1) (1,1) Participant (0,N) Cashier Cardinalities Cardinalities Indicate how many instances of one entity can be Indicate linked to one specific instance of another entity linked In a relational database • Each entity is a table • Each instance is a row in that table Therefore, in relational databases cardinalities Therefore, indicate how many rows in one table can be linked to each row in another table each Cardinalities Cardinalities The first number is the minimum cardinality The minimum • Indicates whether a row in that table must be linked to at least one row in the Indicates other table other • 0 means a new row can be added to that table without being linked to any specific rows in the other table specific • 1 means that each row in that table must be linked to at least one row in the means other table other The second number is the maximum cardinality The maximum • Indicates whether a row in that table can be linked to more than one row in the Indicates other table other • 1 means each row in that table can be linked to, at most, only one row in the other table other • N means that each row in that table can (but need not) be linked to more than means one row in the other table one Three Types of Relationships Three A one-to-one (1:1) relationship • Exists when the maximum cardinality for each entity in Exists that relationship is 1 that A one-to-many (1:N) relationship • Exists when the maximum cardinality of one entity in the Exists relationship is 1 and the maximum cardinality for the other entity in that relationship is N entity A many-to-many (M:N) relationship • Exists when the maximum cardinality for both entities in Exists the relationship is N the Three Types of Relationships Three Cardinalities Relationship Cardinalities Relationship Cardinalities Relationship (0,N) (0,N) (0,1) (0,N) (0,1) (0,1) Revenue Cycle REA Diagram Revenue (Batini min max method - fig. 15-6) Events InventoryOrders (0,N) Customer Orders (1,1) (1,1) (0,1) Participant Inventory (0,N) InventorySales Leads to (0,N) (0,N) Participant (1,1) (1,N) Sales (1,1) (0,N) Sales-Cash Receipts (1,N) Cash Receipts (1,1) Participant (0,N) (0,N) Participant Customer Salesperson Participant (0,N) Resources Agents Customer (1,N) (0,1) Cash (0,N) Stockflow (1,1) (1,1) Participant (0,N) Cashier (Romney & Steinbart/Oracle graphical method - fig. 15-6) Revenue Cycle REA Diagram Revenue Implementing an REA Diagram in a Relational Database Relational Create a table for each distinct entity and for each Create many-to-many relationship many-to-many Assign attributes to appropriate tables Use foreign keys to implement one-to-one and oneto-many relationships REA Diagrams REA Useful for the Access assignment Read chapter 15 prior to beginning the Access Read assignment assignment END OF CHAPTER 15 END ...
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This note was uploaded on 10/02/2010 for the course ACCT 5457 taught by Professor Polm during the Fall '10 term at Rensselaer Polytechnic Institute.

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