OOSAD Resit Exam 2009

The following parts to this question look at differences between related terms and should all be illustrated with supporting examples:

• Explain the difference between an object and a class
• Explain the difference between an Include Relationship and an Extends Relationship in a use case diagram
• Explain the difference between aggregation and generalization
• Explain the difference between an architecture and a framework

In the lectures for this module you were introduced to a four phase model for a traditional Software Development Life Cycle (SDLC), namely Systems Planning and Selection, Systems Analysis, Systems Design and System Implementation and Operation. You were also introduced to an Object Oriented model for the SDLC which also had four phases.

• What are the processes and goals of the four traditional components?
• What are the names, processes and goals of the four Object Oriented components?
• Draw a diagram mapping the workflow/effort between these two approaches

Explain the purpose and use of the following UML diagrams, giving supporting examples as part of your answer:

• The Communication diagram
• The State diagram/State charts
• The Class diagram

Having analysed the requirements for a project, the next stage is to generate the alternative design strategies/ways of getting the required software for the project. Outline the process by which this is done.

Five ways in which you can get software for a project are:

• IT Service Firms
• Packaged Software Providers
• Custom Software Producers
• Open Source Software
• In-house Development

Provide a brief description of each of these approaches and state one advantage and one disadvantage of each.

This is a question on sequence diagrams. The use case diagram for part of an electronic point-of-sale (ePOS) system is shown in Figure 1. See image.

The sequence of events of the Check and Get Pin use case is triggered when the sales person enters the item details and total cost into an order form. The card reader prompts for the card, reads the card then prompts the user to press the OK (or Cancel) button to confirm the purchase. It then expects a four digit PIN (personal identification number) to be entered. Failure to enter a four digit number will result in the user being re-prompted for the PIN up to an extra two attempts (the card reader handles this automatically, failure is the same as pressing cancel button in the previous step). On successful completion, it will request that the credit card company verifies the card is valid for that amount and request the payment. The police may be called if the card is identified as stolen.

From the diagram and the description above, draw a sequence diagram which illustrates the Check and Get Pin use case when a transaction is successful. Obviously you will have to make assumptions about what objects are in the system and what messages will be required in order to complete the diagram.