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Tutorial Exercises

Questions from Week 1

Questions from Week 2

Questions from Week 3

Questions from Week 4

Questions from Week 5

Questions from Week 6

Questions from Week 1

bulletFrom your own practical experience, describe the disadvantages of the conventional approach to systems development.
bulletFrom the point of view of management, what are the major drawbacks of the conventional approach?
bulletWhat major benefits can be attributed to the N.C.C. standards approach to systems development?
bulletIn your opinion, are the criticisms given above fair? Explain.
bulletTo what extent are the criticisms of this method dependent upon its being a manual documentation approach and, hence, would be ameliorated in a machine implementation?

To help you answer these questions you should look over the notes you took in the first lecture (25/01/1999). Also, you might light to look over my own potted history of system design.

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Questions from Week 2

bulletWhat do you understand by the term top-down design?
bulletWhy does Jackson think the practice of top-down design is 'psychologically unrealistic'?
bulletIn systems design problems traditional top-down methods impose a hierarchical structure on the environment in question. What is the major drawback of this approach?
bulletHow does top-down enforce the 'riskiest ordering of decisions'?

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Questions from Week 3

bulletWhy might we consider the software development process to be a feedback process?
bulletShould we use the functional requirements as the focus for system design?
bulletWhat role do assumptions play in system design?

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Questions from Week 4

bulletWhy is it claimed that JSD facilitates system maintenance? If the claim is true, what is its significance?
bulletHow would you explain the statement 'a JSD model is a realisation of an abstract description of the real world'?
bulletUse simple (???) payroll system to show how the validity of the system's outputs is crucially affected by the quality of the model or simulation of the real world.
bulletIf the system developer and the user have different understandings of the computer system's behaviour, any information produced by the system is suspect. Is this statement correct? Does JSD do anything to help overcome this problem?

Using information from the Stitch in Time case study:

bulletDraw up a candidate list of events
bulletDraw up a candidate list of entities

What entities will you reject from your model, and why?

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Questions from Week 5

Exercise 1 - Actions & Entities

From the following brief description, separate out phrases which indicate the major nouns (to identify entities) and the verbs (to identify actions). From these:

  1. Produce an action list to the entities you have discovered;
  2. Allocate the actions to the entities you have discovered;
  3. Produce entity (process) structure diagrams for the entities;
  4. Produce the equivalent structure text.

A certain machine is used to either make or finish components. The machine is set up at the start of each day by an operator. When the machine is used for making new components it is loaded with raw materials; when used for finished components that have already been made it must obviously be loaded with the unfinished components. A product must be ordered before it is made and it is put into a warehouse after it has been finished and inspected before being delivered. If it is found faulty at inspection, it may be re-finished or rejected. If re-finished, it is assumed to be fit for delivery.

Exercise 2 - Backtracking

The life history of the entity HND-student contains the following possible events:

  1. applies for a course;
  2. enrols for the course;
  3. progresses to the 2nd year;
  4. turns down an offer of a place;
  5. withdraws during the 1st year;
  6. withdraws during the 2nd year;
  7. passes exams into 2nd year;
  8. fails exams in 2nd year;
  9. accepted for course;
  10. rejected for course.
bulletDraw a process structure diagram for the student entity without using backtracking.
bulletProduce the equivalent structure text for the student entity.
bulletRedraw the diagram using backtracking.
bulletProduce the equivalent structure text for the backtracking version.

Exercise 3 - Network model

Competitors for a motoring speed trial start from a single grid position at different times and complete four laps which vary in length as different parts of the circuit are brought into use. As each car passes the checkpoint/finish a radio signal relays car identification and time of day. Marshals signal the starting time as each competitor sets off. Points are scored as a function of time taken. On the assumption that each record is sent to a single queue and that all competitors who start also finish, produce an initial network model for a system which will calculate each competitors final score for public display.

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Questions from Week 6

Read through the Poly Fleet Hire case study (Acrobat 3.01 format), then:

bulletAmend the specification so that a report can be generated which provides a list of all those completed car hirings that lasted for more than eight days in the last nine months. The report process is to be run at the manager's discretion (i.e., it is not a scheduled process).
bulletMake sure you draw/amend any structure diagrams & structure texts as necessary.

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