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10 Chapter 10: The Traditional Approach to Design Systems Analysis and Design in a Changing World, 3 rd Edition.

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Presentation on theme: "10 Chapter 10: The Traditional Approach to Design Systems Analysis and Design in a Changing World, 3 rd Edition."— Presentation transcript:

1 10 Chapter 10: The Traditional Approach to Design Systems Analysis and Design in a Changing World, 3 rd Edition

2 10 Systems Analysis and Design in a Changing World, 3rd Edition 2 Learning Objectives u Develop a system flowchart u Develop a structure chart using transaction analysis and transform analysis u Write pseudocode for structured modules

3 10 Systems Analysis and Design in a Changing World, 3rd Edition 3 Overview u Traditional approach to designing software l Overview of structured models, model development process, related terminology l How data flow diagrams are annotated with automation boundary information l How analysis phase models are transformed into design models using system flowcharts, structure charts, and module pseudocode l Integration into other design phase activities l Applying approach to a three-layer architecture

4 10 Systems Analysis and Design in a Changing World, 3rd Edition 4 The Structured Approach to Designing the Application Architecture u Application software programs l Designed in conjunction with database and user interface l Hierarchy of modules u Design internal logic of individual modules u Top-down approach l DFDs with automation boundaries l System flowcharts, structure charts, pseudocode

5 10 Systems Analysis and Design in a Changing World, 3rd Edition 5 Structured Design Models

6 10 Systems Analysis and Design in a Changing World, 3rd Edition 6 The Automation System Boundary u Partitions data flow diagram processes into manual processes and automated systems u Processes can be inside or outside boundary u Data flows can be inside and outside of boundary l Data flows that cross system boundary represent inputs and outputs of system l Data flows that cross boundaries between programs represent program-to-program communication

7 10 Systems Analysis and Design in a Changing World, 3rd Edition 7 DFD with Automation System Boundary

8 10 Systems Analysis and Design in a Changing World, 3rd Edition 8 The System Flowchart u Representation of various computer programs, files, databases, and associated manual processes that make up complete system u Frequently constructed during analysis activities u Graphically describes organization of subsystems into automated and manual components u Can show type of transaction processing system l Batch l Real time

9 10 Systems Analysis and Design in a Changing World, 3rd Edition 9 Common System Flowchart Symbols

10 10 Systems Analysis and Design in a Changing World, 3rd Edition 10 Sample System Flowchart for Payroll System

11 10 Systems Analysis and Design in a Changing World, 3rd Edition 11 System Flowchart for RMO

12 10 Systems Analysis and Design in a Changing World, 3rd Edition 12 The Structure Chart u Describes functions and subfunctions of each part of system u Shows relationships between modules of a computer program u Simple and direct organization l Each module performs a specific function l Each layer in a program performs specific activities u Chart is tree-like with root module and branches

13 10 Systems Analysis and Design in a Changing World, 3rd Edition 13 A Simple Structure Chart for the Calculate Pay Amounts Module

14 10 Systems Analysis and Design in a Changing World, 3rd Edition 14 Structure Chart Symbols

15 10 Systems Analysis and Design in a Changing World, 3rd Edition 15 Structure Chart for Entire Payroll Program

16 10 Systems Analysis and Design in a Changing World, 3rd Edition 16 Developing a Structure Chart u Transaction Analysis l Uses system flow chart and event table inputs l Upper-level modules developed first l Identifies each transaction supported by program u Transform Analysis l Uses DFD fragments for inputs l Computer program ‘transforms’ inputs into outputs l Charts have input, calculate, and output subtrees

17 10 Systems Analysis and Design in a Changing World, 3rd Edition 17 Event-partitioned DFD for the Order-Entry Subsystem

18 10 Systems Analysis and Design in a Changing World, 3rd Edition 18 High-level Structure Chart for the Customer Order Program

19 10 Systems Analysis and Design in a Changing World, 3rd Edition 19 Steps to Create a Structure Chart from a DFD Fragment u Determine primary information flow l Main stream of data transformed from some input form to output form u Find process that represents most fundamental change from input to output u Redraw DFD with inputs to left and outputs to right – central transform process goes in middle u Generate first draft structure chart based on redrawn data flow

20 10 Systems Analysis and Design in a Changing World, 3rd Edition 20 The Create New Order DFD Fragment

21 10 Systems Analysis and Design in a Changing World, 3rd Edition 21 Exploded View of Create New Order DFD

22 10 Systems Analysis and Design in a Changing World, 3rd Edition 22 Rearranged Create New Order DFD

23 10 Systems Analysis and Design in a Changing World, 3rd Edition 23 First Draft of the Structure Chart

24 10 Systems Analysis and Design in a Changing World, 3rd Edition 24 Steps to Create a Structure Chart from a DFD Fragment ( continued ) u Add other modules l Get input data via user-interface screens l Read from and write to data storage l Write output data or reports u Add logic from structured English or decision tables u Make final refinements to structure chart based on quality control concepts

25 10 Systems Analysis and Design in a Changing World, 3rd Edition 25 The Structure Chart for the Create New Order Program

26 10 Systems Analysis and Design in a Changing World, 3rd Edition 26 Combination of Structure Charts

27 10 Systems Analysis and Design in a Changing World, 3rd Edition 27 Evaluating the Quality of a Structure Chart u Module coupling l Measure of how module is connected to other modules in program l Goal is to be loosely coupled u Module cohesion l Measure of internal strength of module l Module performs one defined task l Goal is to be highly cohesive

28 10 Systems Analysis and Design in a Changing World, 3rd Edition 28 Examples of Module Cohesion

29 10 Systems Analysis and Design in a Changing World, 3rd Edition 29 Module Algorithm Design: Pseudocode u Describes internal logic of software modules u Variation of structured English that is closer to programming code u Syntax should mirror development language u Three types of control statements used in structured programming: l Sequence: sequence of executable statements l Decision: if-then-else logic l Iteration: do-until or do-while

30 10 Systems Analysis and Design in a Changing World, 3rd Edition 30 Integrating Structured Application Design with Other Design Tasks u Structure chart must be modified or enhanced to integrate design of user interface and database l Are additional modules needed? l Does pseudocode in modules need modification? l Are additional data couples needed to pass data? u Structure charts and system flowcharts must correspond to planned network architecture l Required protocols, capacity, and security

31 10 Systems Analysis and Design in a Changing World, 3rd Edition 31 Three-Layer Design u Three-layer architecture: l View layer, business logic layer, and data layer u Structure charts and system flowcharts describe design decisions and software structuring u Employs multiple programs for user interface, business logic, and data access modules u Modules in different layers communicate over real-time links using well-defined protocols

32 10 Systems Analysis and Design in a Changing World, 3rd Edition 32 System Flowchart Showing Three-Layer Architecture for Customer Order

33 10 Systems Analysis and Design in a Changing World, 3rd Edition 33 Structure Chart Showing Three-Layer Architecture for Create New Order

34 10 Systems Analysis and Design in a Changing World, 3rd Edition 34 Summary u For traditional structured approach to systems design, primary input is data flow diagram l DFD is enhanced by adding system boundary l Designer describes processes within each DFD boundary using one or more structure charts u Structure charts developed using: l Transaction analysis – multiple transaction types l Transform analysis – single transaction from input to output

35 10 Systems Analysis and Design in a Changing World, 3rd Edition 35 Summary ( continued ) u Structure charts may be based on three-layer architecture l Modules will be clearly identified by layer l Structure chart may be decomposed if layers execute on multiple systems u Structured design may also include: l System flowcharts to show data movement l Module pseudocode to describe internal logic of structure chart module


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