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6 Chapter 6: The Traditional Approach to Requirements Systems Analysis and Design in a Changing World, 3rd Edition www.goupee.com
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6 Learning Objectives Explain how the traditional approach and the object-oriented approach differ when an event occurs List the components of a traditional system and the symbols representing them on a data flow diagram Describe how data flow diagrams can show the system at various levels of abstraction Systems Analysis and Design in a Changing World, 3rd Edition 2
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6 Learning Objectives (continued) Develop data flow diagrams, data element definitions, data store definitions, and process descriptions Develop tables to show the distribution of processing and data access across system locations Read and interpret Information Engineering models that can be incorporated within traditional structured analysis Systems Analysis and Design in a Changing World, 3rd Edition 3
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6 Overview What the system does what an event occurs: activities and interactions Traditional structured approach to representing activities and interactions Diagrams and other models of the traditional approach RMO customer support system example shows how each model is related How traditional and IE approaches and models can be used together to describe system Systems Analysis and Design in a Changing World, 3rd Edition 4
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6 Traditional and Object-Oriented Views of Activities Systems Analysis and Design in a Changing World, 3rd Edition 5
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6 Requirements Models for the Traditional and OO Approaches Systems Analysis and Design in a Changing World, 3rd Edition 6
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6 Data Flow Diagrams Graphical system model that shows all main requirements for an IS in one diagram Inputs / outputs Processes Data storage Easy to read and understand with minimal training Systems Analysis and Design in a Changing World, 3rd Edition 7
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6 DFD Integrates Event Table and ERD Systems Analysis and Design in a Changing World, 3rd Edition 10
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6 DFD and Levels of Abstraction Data flow diagrams (DFDs) are decomposed into additional diagrams to provide multiple levels of detail Higher level diagrams provide general views of system Lower level diagrams provide detailed views of system Differing views are called levels of abstraction Systems Analysis and Design in a Changing World, 3rd Edition 11
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6 Context Diagrams DFD that summarizes all processing activity Highest level (most abstract) view of system Shows system boundaries System scope is represented by a single process, external agents, and all data flows into and out of the system Systems Analysis and Design in a Changing World, 3rd Edition 13
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6 DFD Fragments Created for each event in the event table Represents system response to one event within a single process symbol Self contained model Focuses attention on single part of system Shows only data stores required to respond to events Systems Analysis and Design in a Changing World, 3rd Edition 14
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6 DFD Fragments for Course Registration System Systems Analysis and Design in a Changing World, 3rd Edition 15
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6 Event-Partitioned System Model DFD to model system requirements using single process for each event in system or subsystem Decomposition of the context level diagram Sometimes called diagram 0 Used primarily as a presentation tool Decomposed into more detailed DFD fragments Systems Analysis and Design in a Changing World, 3rd Edition 16
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6 Context Diagram for RMO Customer Support System Systems Analysis and Design in a Changing World, 3rd Edition 18
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6 Context Diagram for RMO Order-Entry Subsystem Systems Analysis and Design in a Changing World, 3rd Edition 20
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