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Chapter 9 & 10 con’t

Chapter 9 & 10 con’t. Moving to Design & The Traditional Approach to Design. Objectives. Discuss the issues related to the design phase of the SDLC Develop a system flowchart Develop a structure chart using transaction analysis and transform analysis

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Chapter 9 & 10 con’t

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  1. Chapter 9 & 10 con’t Moving to Design & The Traditional Approach to Design

  2. Objectives • Discuss the issues related to the design phase of the SDLC • Develop a system flowchart • Develop a structure chart using transaction analysis and transform analysis • Write pseudo code for structured modules

  3. Analysis Objectives to Design ObjectivesFigure 9-2

  4. Moving from Analysis to Design • Design: • Converts functional models from analysis into models that represent the solution • Focused on technical issues • Requires less user involvement than analysis • Questions • What components require systems design? • How is the system going to be integrated?

  5. SDLC Phases with Design Phase Activities Design and Integrate Network Design the Application Architecture Design the User Interfaces Design the System Interfaces Design and Integrate the Database Prototype for Design Details Design and Integrate System Controls

  6. Components Requiring Systems DesignFigure 9-1

  7. Middleware “Software that implements communication protocols and helps different systems communicate.”

  8. Class Exercise • Draw on the board a ecommerce website that includes main web server, access to a product database, software / driver downloads (ftp), online ordering. • Which portions of the 3 layer client server diagram (next slide) correspond to each?

  9. Three-Layer Client Server Architecture

  10. Structured Design Models

  11. Automation System Boundary • Partitions data flow processes into manual and automated systems • Processes can be inside or outside boundary • Data flows can be inside and outside of boundary representing interfaces to users and other systems

  12. DFD with Automation System Boundary Automation Boundary: Partitions data flow processes into manual and automated systems

  13. Common System Flow Chart Symbols Figure 9-9 Systems Flow Chart Components “A diagram that describes overall flow of control between computer programs / subprograms/ files/databases.” Processing within the system is divided up into discrete steps.

  14. System Flow Chart Where is the automation boundary?

  15. Structure Chart • Describes functions and sub-functions of each part of system • Shows relationships between modules of a computer program • Simple and direct method • Each module performs a specific function • Each layer in a program performs specific activities

  16. Structure Chart Symbols E.g., print routine for several forms Data Flow (program call) Embedded (e.g., check printer status portion of a print module) Decision Iterative Leaf modules Principles: each module has a distinct function, higher modules call lower modules

  17. Creating a Structure Chart • Transaction Analysis: What transactions must occur. For example to purchase a book online: 1) get book to be ordered information 2) get credit card information, 3) get shipping information, 4) validate credit card, 5) print receipt. • Transform Analysis: How data is transformed by the system. For example to purchase a book online: 1) afferent data flow ->get ordering information (book information, shipping etc.), central transformation -> process order (credit card, inventory check etc.), efferent data flow -> create order receipt.

  18. Rat System Structure Chart Output Input Fundamental Flow High Module Cohesion? Loosely coupled? On left?

  19. Pseudo code • Near English text that closely resembles programming. ! Determine if switch press is correct () Get switch input() If correct activate feeder() Else activate shock() Endif • Develop the pseudo code required to calculate the median of a group of numbers

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