CpSc 472/672

Exam 2

 

Name______________________________________________

 

This is an open notes exam. It is an individual effort.

 

There are 6 questions on the exam. Answer 5 of the questions. Be certain to answer all parts of the questions that you select. Put a large X on the question you are omitting. Do not answer all 6 and expect me to pick the 5 best. If you answer 6, I will pick the WORST 5. Make a decision on which you will answer.

 

You have until 10:15am to complete the exam.

 

 

 

 

  1. The software architecture is the basic structure of a software system.
    1. Describe how an architect decides to define a specific module in the architecture.
    2. The architecture is intended to satisfy the system’s requirements. How are the requirements represented in the architecture?
    3. Assume the architect chooses to use an event-based architecture style. Compared to a style in which one module directly invokes another by making a function call, what system qualities does the event-based architecture enhance that the direct invocation architecture degrades?

 

 

 

 

  1. Process definitions have different levels of detail. A basic process definition is divided into phases, each phase is divided into activities, and each activity is divided into a set of steps. Each of these divisions can be written as a process in its own right.
    1. Every phase has an exit criterion. Describe the purpose of the exit criterion and give an example.
    2. At a high level the software development process is: analysis, design, implementation, and testing. Explain why this is a natural sequence for solving a problem.
    3. The requirements process has two main activities: elicitation and analysis. Explain why it is useful to divide “writing the requirements” into these two activities.

 

 

 

  1. The OCL is used to express constraints about actions in the system. Pre-conditions and post-conditions describe expected states of the system before an operation and immediately after. OCL is also used to describe invariants. 
    1. Describe the difference between a defensive design approach and a design by contract approach.
    2. What is the difference between a pre or post-condition and an invariant?
    3. Given the OCL expressions below, explain what each OCL constraint means.

 

context Person inv:

            self.age>0

 

context Job::increaseSalary(percentage: Integer)

            pre: 0 < percentage and percentage <= 100

            post: salary = salary@pre*(1+percentage/100)

 

 

  1. UML allows us to model concepts and the relationships among those concepts. We apply three criteria to models comprised of UML diagrams correctness, completeness, and consistency.
    1. Explain why a model should meet each of the three criteria and give an example of how each criterion can be violated in a model.
    2. Consider the situation in which a building architect wishes to describe the contents of a typical classroom. Draw the UML diagram that represents the contents and the relationships among the various pieces.
    3. Draw the state transition diagram that shows the operation of a room light where there are two switches that control the light. Each time either switch is thrown the light changes state. If I walk in one door and flip the switch and the light is off, it will come on. Then if I walk out the other door and flip the switch the light goes off. If I walk in a door and the light is on and flip the switch, the light goes off and when I flip the other switch the light comes on.

 

 

 

 

 

 

  1. A “component model” describes the underlying characteristics of families of components. We briefly discussed the J2EE, CORBA and .NET models.
    1. Describe some attributes that vary from one component model to another. Explain why each attribute is sufficiently significant to be a difference between models. Illustrate each attribute using the J2EE model.
    2. A module is considered good if there is low coupling and high cohesion. Why are these characteristics desirable?
    3. What is the role of a Broker in the interaction between two components?

 

 

  1. The most recent assignment was to design a “to do list” program.
    1. Describe how the requirement to “print all the tasks” could be designed.
    2. Describe one design pattern used in your design. Why is it helpful to use design patterns?
    3. Design an extension to your design that allows the user to copy a task that is in the list and paste it into the list at a different point.