Systems Design, Implementation, Maintenance, and Review

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Systems Design

Systems Design
A phase in the development of an IS system that answers the question “How will the information system do what it must do to obtain a solution to a problem?”
Logical Systems Design
Describes the functional requirements of a systems.
Physical Systems Design
Specifies the characteristics of the system components necessary to put the logical design into action.

Logical Design Elements

Physical Design Elements

Procedures for Signing On (Figure 13.1) 3 steps to signing onto a secure system

Sign-on Procedure
Safeguards needed for an individual to gain access to computer resources.
Systems Sign-on
Allows user to gain access to the computer system.
Application Sign-on
Permits the user to start and use a particular application.

Interactive processing People interact directly with the processing component of the system.

Designing good interactive dialogue

Dialogue
The series of messages and prompts communicated between the system and the user.

Preventing, detecting, and correcting errors Best time to deal with potential errors is at the beginning of design rather than in the late part of design, or during implementation.

Causes of System Error

Emergency Alternative Procedures and Disaster Recovery

Software and database backup

Emergency Alternative Procedures and Disaster Recovery

Systems Controls

Importance of Vendor Support

Request For Proposal (RFP) A document that specifies in detail required resources such as hardware and software

Financial Options to Acquire Computer Systems (Table 13.2)

Evaluating and Selecting a System Design (Figure 13.4) Number of alternatives goes down as system is developed. Highest in Investigation phase, lower in Analysis Phase, few in Implementation Phase

Preliminary Evaluation
Evaluation that begins after all proposals have been submitted for the purpose of dismissing unwanted proposals.
Final Evaluation.
Detailed investigation of the proposals offered by remaining vendors.

Evaluation Techniques (Table 13.3)

Evaluation Techniques (Figure 13.5)

Freezing Design Specifications

The Contract

Design Report (Figure 13.6)

Systems Implementation (Figure 13.7)

  1. Includes hardware acquisition or development,
  2. user preparation,
  3. hiring and training of personnel,
  4. site and data preparation,
  5. installation,
  6. testing,
  7. start-up
  8. user acceptance.

The Make-or-Buy Software Decision

Building Own Software (Make)
IS Educated staff
Buying Own Software (Buy)
Review needs of requirements Acquire software Modify or customize software Acquire software interfaces Test and accept the software Maintain the software and make necessary modifications
Software Interface
Program modifications that allow proprietary software to work with other software used in the organization..

In-House Developed Software (Figure 13.8)

Picture of Programming Life Cycle Series of steps and planned activities developed to maximize the likelihood of developing good software.

Documentation

Tools and Techniques for Software Development

Usage of Tools by Systems Analysts (Table 13.4) Percentages. Most use something.

Structured Programming ConstructsThe picture shows Sequence, Selection, and Iteration, the three constructs allowed in structured programming.

Structured Programming is a way of developing code that provides structure within the program so that testing and maintenance tasks are facilitated.

Characteristics of Structured Programming and the Top-Down Approach (Table 13.5 and Figure 13.11)

Other Tools and Techniques for Software Development

Structured Walkthrough (Figure 13.12) A planned and pre-announced review of the progress of a program module, a structure chart, or a human procedure.

Other Steps in the Systems Development Effort

Types of Testing (Figure 13.13)

Unit testing
Testing of individual programs.
System Testing
Testing the entire system of programs.
Volume testing
Testing the application with a large amount of data.
Integration testing
Testing all related systems together.
Acceptance testing
Conducting any tests required by the user.

Start-Up Approaches (Figure 13.14)

Start-Up Approach Procedures that begin with the final tested information system; when start-up is finished, the system will be fully operational.

Systems Maintenance

Reasons for Maintenance

Type of Maintenance

Maintenance Cost as a Function of Age (Figure 13.15) Graph shows maintenance cost increasing with age. Actually, high cost at first, then low, then gradual increase.

The Value of Investment in Design (Figure 13.16) A really bad graph showing that spending more on design increases total development cost and decreases total maintenance cost and total overall SLC cost.

Systems Review

Factors to Consider During System Review

  • Mission
  • Organizational goals
  • Hardware and software
  • Database
  • Telecommunications
  • Information systems personnel
  • Control
  • Training Costs
  • Complexity
  • Reliability
  • Efficiency
  • Response time
  • Documentation

Systems Performance Measurement