Chapter 6 - General Systems Design

A) Introduction

B) What are the three categories of Systems Design?

  1. Global-based systems

    involves a complete overhaul or replacement of all the systems design components

    examples:

    need a General Systems Design Worksheet (Fig. 6.3)

  2. Group-based systems
    services a branch office or department
  3. Local-based systems
    designed for a few people
    ex. EIS for senior executives

C) Using the Four Key Elements of Rapid Application Development to Design Systems

  1. RAD combines elements that work together so that the total effect is greater than the sum of the individual effects
    Dillinson's Department Store - pg. 201-3
  2. Joint application development (JAD)

    best with global-based systems

    need to bring together

  3. Specialists with advanced tools (SWAT) teams

    3-4 highly skilled and motivated systems professionals using CASE

  4. Prototyping

    users are shown what they're going to get

D) Using the Structure-Oriented Design Approach to Design Systems

process-oriented approach

data-oriented approach

used if processes, inputs and outputs are less defined

Create the Data Dictionary for the Systems

E) Using the Object-Oriented Design Approach to Design Systems

Designing & Building Systems Using Reusable Software Objects

What are the Key Elements of Object-Oriented Design?

  1. Objects - "entity" with behaviours (methods)
  2. objects behave in response to messages
  3. classes - set of objects that share a common structure and behavior
  4. inheritance - sharing of properties with subclasses
  5. polymorphism - ability of objects to respond to the same message and implement it differently (ex. +)

What Steps are Required to Perform Object-oriented Design at the General Systems Design Level?

F) What is the Difference between Structure-oriented and Object-oriented design?

"controlling the amount and form of communication between modules is the essence of modularity, and the key objective of modularity is autonomous, stand-alone modules" (Fig. 6.17)
  • Top-down vs. bottom-up design
  • Using Existing Object Class Libraries (reusability)

    Exercises: look over 1-14 ; turn in 6.15, 6.16, 6.19

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