265 - Text - Chapter 3

265 - Text - Chapter 3 - Chapter 3: Logical Design for...

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Chapter 3: Logical Design for Database Systems 1 of 43 ADVANCED SYSTEMS ANALYSIS & DESIGN by: Uday S. Murthy , Ph.D., ACA Logical Design for Database Systems Learning Objectives After studying this chapter you should be able to: distinguish between logical and physical database models describe the entity-relationship and extended entity-relationship logical modeling approaches describe the elements of data-flow diagrams distinguish between different levels of data-flow diagrams , such as context diagrams, Level 0, and Level 1 data flow diagrams identify entities and relationships in a business environment using an event- oriented focus construct an extended entity relationship diagram based on a narrative description of a business scenario construct context diagrams and data-flow diagram s based on a description of a business process In the previous chapter, you learned about the systems development life-cycle with specific reference to database systems. To reiterate, systems analysis involves understanding the existing system. The systems design stage involves logical and physical design -- developing data and process models for the proposed system, from which physical models suitable for implementation are created. Systems development involves actually creating the data structures and programming, systems implementation involves converting from the old to the new system, and finally systems operation and maintenance involves actually using the new system and fine tuning it. As was indicated in the previous chapter, an in-depth discussion of systems analysis, implementation, and operation and maintenance would be beyond the scope of this book, and would also be very situation-specific. This chapter focuses on logical design for the development of database systems and has two main objectives: (1) describe two commonly used logical modeling tools for systems design -- Entity-Relationship (ER) modeling and data-flow diagrams (DFD), and (2) provide specific guidelines using an "event-oriented" approach to facilitate the construction of ER models and DFDs for business/accounting scenarios.
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Chapter 3: Logical Design for Database Systems 2 of 43 In the systems analysis stage, analysts examine the current system and interview users to determine their information needs. The result of this analysis is usually a narrative description of a business scenario, sometimes accompanied by a flowchart. The question, then, is how exactly does one go from narrative descriptions of business scenarios to a functioning database system. Moving from systems analysis to logical systems design, the focus turns to the creation of logical models that are pictorial representations of users' information needs. The two aspects of logical design are logical data modeling and logical process modeling. We will explain logical data modeling using the entity-relationship (ER) approach. You might recall that we briefly introduced ER modeling in the previous chapter. Logical process modeling will be explained using
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This note was uploaded on 08/12/2008 for the course MBA 265 taught by Professor James during the Spring '08 term at CSU Sacramento.

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265 - Text - Chapter 3 - Chapter 3: Logical Design for...

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