1. 10 ITK261 The traditional approach to design Reading: Chapter 10 Oct 9, 11

2. 10 Systems Analysis and Design in a Changing World, 4th Edition 2 Announcements u Change of office hours l Tues: 10:30AM – 12:00PM l Thurs: 10:30AM – 12:00PM l Wed: 1:30 – 2:30PM u Visit from State Farm Insurance company (Kentrica Coleman) l Want to submit your resume? l This Thursday (Oct 11) u Assignment #2 l Will be given on Thursday l Focus: Chapter 5 and 6 (e.g., data flow diagram, ER diagram etc)

3. 10 Systems Analysis and Design in a Changing World, 4th Edition 3 Learning Objectives u Describe the steps involved in the traditional approach to designing the application architecture u Develop a system flowchart u Develop a structure chart using transaction analysis and transform analysis u Write pseudocode for structured modules u Explain how to use three-layer design with the traditional approach

4. 10 Systems Analysis and Design in a Changing World, 4th 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, 4th Edition 5 Structured Design Models

6. 10 Systems Analysis and Design in a Changing World, 4th 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, 4th Edition 7 DFD with Automation System Boundary (Figure 10-2)

8. 10 Systems Analysis and Design in a Changing World, 4th 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, 4th Edition 9 Common System Flowchart Symbols

10. 10 Systems Analysis and Design in a Changing World, 4th Edition 10 Sample System Flowchart for Payroll System (Figure 10-4)

11. 10 Systems Analysis and Design in a Changing World, 4th Edition 11 System Flowchart for RMO (Figure 10-5)

12. 10 Systems Analysis and Design in a Changing World, 4th 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, 4th Edition 13 A Simple Structure Chart for the Calculate Pay Amounts Module

14. 10 Systems Analysis and Design in a Changing World, 4th Edition 14 Structure Chart Symbols

15. 10 Systems Analysis and Design in a Changing World, 4th Edition 15 Structure Chart for Entire Payroll Program

16. 10 Systems Analysis and Design in a Changing World, 4th Edition 16 Developing a Structure Chart u Transaction analysis l Uses system flow chart and event table as inputs l Upper-level modules developed first l Identifies each transaction supported by program u Transform analysis l Uses DFD fragments as 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, 4th Edition 17 Event-partitioned DFD for the Order-Entry Subsystem (Figure 10-9)

18. 10 Systems Analysis and Design in a Changing World, 4th Edition 18 High-Level Structure Chart for the Order-Entry Subsystem After Transaction Analysis

19. 10 Systems Analysis and Design in a Changing World, 4th 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 of structure chart based on redrawn data flow

20. 10 Systems Analysis and Design in a Changing World, 4th Edition 20 The Create New Order DFD Fragment

21. 10 Systems Analysis and Design in a Changing World, 4th Edition 21 Decomposed DFD for Create New Order

22. 10 Systems Analysis and Design in a Changing World, 4th Edition 22 Rearranged Create New Order DFD

23. 10 Systems Analysis and Design in a Changing World, 4th Edition 23 First Draft of the Structure Chart for Create New Order (Figure 10-14)

24. 10 Systems Analysis and Design in a Changing World, 4th 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, 4th Edition 25 The Structure Chart for the Create New Order Program (Figure 10-15)

26. 10 Systems Analysis and Design in a Changing World, 4th Edition 26 Combination of Structure Charts: Transaction and Transform Analysis (Figure 10-16)

27. 10 Systems Analysis and Design in a Changing World, 4th 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, 4th Edition 28 Examples of Module Cohesion

29. 10 Systems Analysis and Design in a Changing World, 4th 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, 4th 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, 4th 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, 4th Edition 32 System Flowchart Showing Three-Layer Architecture for Customer Order

33. 10 Systems Analysis and Design in a Changing World, 4th Edition 33 Structure Chart Showing Three-Layer Architecture for Create New Order (Figure 10-20)

34. 10 Systems Analysis and Design in a Changing World, 4th 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, 4th 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

36. 10 Systems Analysis and Design in a Changing World, 4th Edition 36 Case study: u We will use handout and blackboard