Se... 303s3e

SWEN 4432 – Assignment 3 – Name Put your answer to each of the questions below immediately after the question. Chapter 7: 1. Requirements Engineering Processes. 1. Suggest who might be stakeholders in a university student records system? Explain why it is almost inevitable that the requirements of the different stakeholders will conflict in some way. As stakeholders are everyone who will be affected in some way, it’s fairly hard to list them all, but some examples would be students, teachers, other faculty relating to the records such as the billing department, government officials in charge of the financial aid given to students who are below a certain number of hours, people of that nature.

The requirements that stakeholders have will conflict in various ways, as different people have different priorities, and some of the stakeholders who influence the design of a system more than others may not know exactly what they really want and need. In the student records system, the requirements of students may be something along the lines of they want to see at any given time what classes are remaining in their curriculum, and the government officials may want to see at any given time the hours of the courses already taken. In an extremely simple records system, these would conflict with each other, and would need each to be built upon to meet the requirements of both parties.

1

2. A software system is to be developed to manage the records of patients who enter a clinic for treatment. The records include records of the all regular patient monitoring (temperature, blood pressure, etc) treatments given, patient reactions and so on. After treatment, the records of their stay are sent to the patient’s doctor who maintains their complete medical record. Identify the principal viewpoints which might be taken into in the specification of this system and organize these using a viewpoint hierarchy diagram.

3. For three of the viewpoints identified in the library system, LIBSYS (Figure 7.4), suggest three requirements that could be suggested by the stakeholders associated with that viewpoint. 2

The doctors may require in depth medical analyses of the patients to be displayed so they can give prognoses easier, the nurses may require previous history of medicine and treatments istered, so they can know what to expect from a patient, and the medical coders may require a complete list of individual services provided to the patient, to know what to enter into the database.

3

4. The LIBSYS system has to include for cataloguing new documents where the system catalog may be distributed across several machines. What are likely to be the most important types of non-functional requirements associated with the cataloguing facilities? I would say the more important types of non-functional requirements would be those relating to the replication of data of the entire system, to the individual machines. Keeping the data consistent and congruent in the entire system would be one of the top goals of the system, as redundancies and omissions could be highly likely in a distributed environment.

5. Who should be involved in a requirement review? Draw a process model showing how a requirement review might be organized. The primary stakeholders should be involved in the requirements review, as well as those involved with the development of the system, and the project managers who are in charge of the budget and scheduling of the system.

4

6. Using your knowledge of how an ATM is used, develop a set of usecases that could serve as a basis for understanding the requirements for an ATM system. 1. The is prompted to enter a card 2. The enters their card 3. The is prompted to enter their PIN 4. The enters their PIN 5. The is prompted to withdraw or check balance 6. The balance is displayed 7. If withdraw is chosen, the is prompted to enter the amount to be withdrawn 5

8. If withdraw is chosen, the amount is compared with the balance, and if enough money is available, the money is dispensed 9. If withdraw is chosen, the is prompted to take the dispensed money 10.The is prompted to take their card 11.All transactions are complete, and display a happy message for the Chapter 8: 2. System Models. 1. Based on your experience with a bank ATM, draw a dataflow diagram modeling the data processing involved when a customer withdraws cash from the machine.

2. Model the data processing that might take place in an email system. You should model the mail sending and mail receiving processing separately.

6

7

3. Draw state machine models of control software for: i. An automatic washing machine that has different programs for different types of clothes

8

ii. The software for a DVD player.

9

iii. A telephone answering system that records incoming messages and displays the number of accepted messages on an LED. The system should allow the telephone customer to dial in from any location, type a sequence of numbers (identified as tones) and play the recorded messages.

10

4. Model the object classes that might be used in an email system. If you have tried Exercise 8.3 (Question 2.2 here) describe the differences between the data processing model and the object model.

They differ in that the data processing model shows how the system would operate; the object model shows the details of the individual components. Both of them together would allow a developer to appropriately produce a system that functions with the properties described in the object model, with the actions described in the data processing model.

11

5. Develop an object model, including a class hierarchy diagram and an aggregation diagram showing the principal components of a personal computer system and its system software.

12

Chapter 11: 3. Architectural design. 1. Explain why it may be necessary to design the system architecture before the specifications are written. It may be necessary to make some decisions on what fundamental designs of system architecture will be implemented, before any specification can be written, as the specifications may rely on the architecture itself, in whole on in part.

2. Construct a table showing the advantages and disadvantages of the structural models discussed in the chapter. Model Type

Strengths

Weaknesses

Repository

Efficient way to share large amounts of data

Subsystems must compromise between specific needs of tools

Client-Server

Distributed design, easy to add and integrate new servers to the system

Changes to clients may be necessary to fully utilize new servers

Layered

s incremental development of systems, very changeable and portable

Difficult to structure, subsystems may have to circumvent model to be effective

3. Giving reasons for your answer, suggest an appropriate structural model for the following systems: i. An automated ticket issuing system at a railway system. Repository. The remote systems would be the actual ticket issuing systems that s will use, and the servers will be central to some location. A minimum of compromises with tools would be necessary.

13

ii. A computer-controlled video conferencing system that allows video, audio and computer data to be visible to several participants at the same time. Client-Server. The video conferencing system would need to collect a large amount of information, and share it to all involved with great speed. Using a central server, with clients connected to it would suit the system well. Changing to a new server wouldn’t affect the clients, so the disadvantages are minimized.

14

4. Explain why it may be necessary to design the system architecture before the specifications are written. Same question as #1.

5. Design an architecture for the above systems based on your choice of model. Made reasonable assumptions about the system requirements.

15

6. Giving reasons for your answer, suggest an appropriate control model for the following systems? i. A batch processing system that takes information about hours worked and pay rates and prints salary slips and bank credit transfer information. The Call-Return model. Efficiency would be better than the other models, as the entire process of calculating and printing can be repeated continuously until all are done, rather than doing each step as a whole, then moving to the next one. ii. A set of software tools that are produced by different vendors, but which must work together. Broadcast model. So long as a system can handle all of the events that the individual tools transmit, the entire system as a whole will work well. iii. A television controller that responds to signals from a remote control unit. 16

Interrupt-driven model. The system does not need to do anything until an event is given as an interrupt to its current state. When an interrupt is given, the appropriate action can be taken.

7. You are given two integrated CASE toolsets and are asked to compare them. Explain how you could use a reference model for CASE (Brown, et al., 1992) to make this comparison. CASE tools don’t always have to contain the same types of tools or work in the same way. Using the reference model with its five sets of services would allow the to determine what CASE tools are missing, and what has been added as extra services to the reference, which could then be used to compare the two toolsets.

17