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Data Modeling and Database Design

Data Modeling and Database Design. 5. Chapter. UAA – ACCT 316 Accounting Information Systems Dr. Fred Barbee. Hmmm? What is data modeling?. ACCT 316 ACCT 316 ACCT 316. What is Data Modeling?. The Blind Men and the Elephant. ACCT 316 ACCT 316 ACCT 316.

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Data Modeling and Database Design

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  1. Data Modeling and Database Design 5 Chapter UAA – ACCT 316 Accounting Information Systems Dr. Fred Barbee

  2. Hmmm? What is data modeling?

  3. ACCT 316 ACCT 316 ACCT 316 What is Data Modeling? The Blind Men and the Elephant

  4. ACCT 316 ACCT 316 ACCT 316 What is Data Modeling? So what! You Say!

  5. ACCT 316 ACCT 316 ACCT 316 What is Data Modeling? Without a model of what we are building, we are like these blind men: we may be partly right, but we are probably mostly wrong.

  6. ACCT 316 ACCT 316 ACCT 316 What is Data Modeling? The elephant – a third grader’s view.

  7. ACCT 316 ACCT 316 ACCT 316 What is Data Modeling? You cannot understand (and thus represent) something unless you comprehend it completely – enterprise-wide.

  8. ACCT 316 ACCT 316 ACCT 316 What is Data Modeling? Plato’s “Myth of the Cave”

  9. Hmmm? What is data modeling?

  10. The Text Definition . . . • Data modeling is the process of defining a database • so that it faithfully represents all aspects of the organization, • including its interactions with the external environment.

  11. Other Definitions . . . • Data modeling is the task of formalizing the data requirements of the business process as a conceptual model. Hall, James A. Accounting Information Systems Southwestern Publishing, 2001

  12. Other Definitions . . . • Data modeling is the process of defining what data you want to capture in your database and the relationships between data. Database Services University of Michigan http://www.umich.edu/~dbsvcs/services/modeling.html

  13. Data Modeling and Database Design 5 Chapter Database Design Process

  14. Planning Requirements Analysis Design Coding Implementation Operation and Maintenance Data Modeling Occurs Here Figure 5-1

  15. ACCT 316 ACCT 316 ACCT 316 The Database Design Process Let’s At each of these steps individually.

  16. Planning Requirements Analysis Initial planning to determine the need for and feasibility of developing a new system. Design Coding Implementation Operation and Maintenance

  17. Planning Requirements Analysis Design Identifying User Needs Coding Implementation Operation and Maintenance

  18. Planning Requirements Analysis Design Developing the contextual-external- and internal-level schemas Coding Implementation Operation and Maintenance

  19. Planning Requirements Analysis Translating the internal-level schema into the actual database structures that will be implemented in the new system. Design Coding Implementation Operation and Maintenance

  20. Planning Requirements Analysis Design Transferring all data from the existing system to the new database. Coding Implementation Operation and Maintenance

  21. Planning Requirements Analysis Design Using and maintaining the new system. Coding Implementation Operation and Maintenance

  22. The Entity-Relationship (E-R) Diagram

  23. Relationship Entity ACCT 316 ACCT 316 ACCT 316 The Entity-Relationship (E-R) Diagram

  24. The REA Data Model

  25. The REA Data Model • The REA data model is a conceptual modeling tool specifically designed to provide structure for designing AIS data bases.

  26. The REA Data Model • The REA data model provides structure in two ways: • By identifying what entities should be included in the AIS database • By prescribing how to structure relationships among the entities in the AIS database

  27. Give-To- Get Duality ACCT 316 ACCT 316 ACCT 316 The REA Data Model Resources Events Agents

  28. ACCT 316 ACCT 316 ACCT 316 The REA Data Model Resources: Those things that have economic value to the firm. Resources Events Agents

  29. ACCT 316 ACCT 316 ACCT 316 The REA Data Model Events: Various Business Activities Resources Events Agents

  30. ACCT 316 ACCT 316 ACCT 316 The REA Data Model Agents: People and Organizations that participate in events. Resources Events Agents

  31. Developing an REA Diagram

  32. Resources Events Agents

  33. Step 1: Identify the Economic Exchange Events 1 • Identify the pair of events that reflect the basic economic exchange (give-to-get duality relationship) in that cycle.

  34. Identify the PAIR of events • One GET • One GIVE

  35. Step 2: Identify Resources and Agents 2 • Identify the Resources affected by each event and the agents who participate in those events.

  36. Identify . . . • RESOURCES affected by each event. • AGENTS who participate in the events.

  37. Step 3: Include commitment Events 3 • Analyze each economic exchange event to determine whether it should be decomposed into a combination of one or more commitment events and an economic exchange event.

  38. Include commitment events.

  39. Step 4: Determine Cardinalities of Relationships 4 • Determine the cardinalities of each relationship.

  40. Determine cardinalities of relationships.

  41. Sales Customer How many sales transactions can be linked to each individual customer? How many customers can be linked to each individual sales transaction?

  42. ACCT 316 ACCT 316 ACCT 316 Cardinalities Minimum (1,N) Maximum

  43. The first number is theminimum cardinality. It indicates whether a row in this table must be linked to at least one row in the table on the opposite side of that relationship.

  44. Minimum Cardinality • The minimum cardinality of a relationship indicates whether each row in that entity MUST be linked to a row in the entity on the other side of the relationship. • Minimum cardinalities can be either 0 or 1.

  45. Minimum Cardinalities • A minimum cardinality of zero means that a new row can be added to that table without being linked to any rows in the other table. • A minimum cardinality of one means that each row in that table MUST be linked to at least one row in the other table

  46. ACCT 316 ACCT 316 ACCT 316 Made to Cardinalities • The minimum cardinality of zero in the (0, N) cardinality pair to the left of the customer entity in the customer-sales relationship . . . Sales (0, N) Customer • . . . indicates that a new customer may be added to the database without being linked to any sales events.

  47. ACCT 316 ACCT 316 ACCT 316 Made to Cardinalities • The minimum cardinality of 1 in the (1,1) cardinality pair to the right of the sales entity in the customer-sales relationship . . . (1,1) Sales (0, N) Customer • . . . indicates that a new sales transaction CAN ONLY be added if it is linked to a customer.

  48. The second number is themaximum cardinality. It indicates whether one row in that table can be linked to more than one row in the other table.

  49. Maximum Cardinalities • The maximum cardinality of a relationship indicates whether each row in that entity CAN be linked to more than one row in the entity on the other side of the relationship. • Maximum cardinalities can be either 1 or N.

  50. Maximum Cardinalities • A maximum cardinality of 1 means that each row in that table can be linked to at most only 1 row in the other table. • A maximum cardinality of N means that each row in that table MAY be linked to more than one row in the other table.

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