August 1999
SD206 : SYSTEMS DESIGN

QUESTION 1 (Compulsory)

Total Marks: 20 Marks

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(a) Define the term system design. [2]
Systems design is the development of a blueprint for a computer-based solution to improve an existing system; it is a bridge between analysis and implementation.

 
(b) (i) Why should output not be created if it is not functional?

(ii) Why is it often difficult to create user-specific output?

 [1]

[1]
(i) Because there are costs associated with all outputs.

(ii) Because large information systems typically serve many different users for many different purposes.
(c) Give two reasons why an effective design should control the quantity of data for input. [2]
  • The costs of data preparation and data entry are high: reducing data requirements can reduce labour costs.
  • Input can be time-consuming: reducing input requirements can lead to speed-up in the entire processes from data capture to output.
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(d) Give two reasons why the development of natural language interfaces has been limited. [2]
  • Problems with implementation
  • Natural language interfaces place an extraordinary demand on computing resources.

 
(e) List three basic rules which should be followed when determining which data should be captured and which data should be left to the system to enter. [3]
  • If the data can be retrieved by the computer, do not let the users enter it.
  • If the information can be computed by the computer, let the machine perform it.
  • If the data is fairly constant, store it in a separate file so that future retrieval can be performed, rather than have it entered every time.
  • If there is a tendency for a certain value to be entered a lot, create a default field with the expected data.

 
(f) Describe the term integrity control. [2]
Integrity control ensure that the data being processed represents the actual, current status . In addition, they are applied to ensure that, if any files are inadvertently destroyed, the materials and mechanisms exist to reconstruct the files and to recover processing capabilities.

 
(g) List two forms of error tolerance. [2]
  • Redundant hardware.
  • Degraded processing.

 
(h) List three drawbacks of fourth generation tools. [3]
  • Many fourth generation tools have limited portability.
  • Many fourth generation tools do not support concurrent updates.
  • Many fourth generation tools are only suitable for small to medium sized applications.
  • Many fourth generation tools only support the implementation phase.

 
(i) Define the term post-implementation evaluation. [2]
A post-implementation evaluation verifies that the new system meets specified requirements and achieves anticipated benefits.