SYSTEM AND DESIGN CHAPTER 5
14. An actor in a use case always represents a specific user.
Ans: False Response: See page 173
8. An alternate or exceptional flow in a use case documents the decomposition of the normal flow of events.
Ans: False Response: See pages 170-171
2. How does a project team go about obtaining the information they need to create use case descriptions?
Ans: The project team must work closely with the users as they develop the use cases. Often the project team will use interviews, JAD sessions, and observation to gain this information. In reality, the techniques are similar to those discussed in Chapter 4 of the text. The key will be keeping in mind that a use case is associated with a role that a person plays in the system, not with a specific person. Response: See pages 167
5. The primary actor is the person or thing that starts the execution of a use case.
Ans: True Response: See page 168
7. Inheritance is supported in use cases through the generalization relationship.
Ans: True Response: See page 170
27. An asterisk on a relationship in a use case diagram represents multiplicity of the association.
Ans: True Response: See page 175-176
15. As you work through the SDLC, it is likely that the system boundaries will change.
Ans: True Response: See pages 179
13. Which of the following relationships describe the communication between the use case and the actors? a. association relationship b. extend relationship c. include relationship d. generalization relationship e. none of the above
Ans: a Response: See page 170
13. An actor in a use case must be a person.
Ans: False Response: See page 173
25. A solid line without arrows between an actor and a use case in a use case diagram represents a one-way flow of communication from the actor to the use case.
Ans: False Response: See page 175
28. When drawing use case diagrams, higher level use cases are drawn below lower level use cases.
Ans: False Response: See page 176
32. Control flows in an activity diagram are shown using solid-lines with arrows while object flows are shown using dashed lines with arrows.
Ans: True Response: See page 160 &162
22. A complex use case is one that has more than _____ unique transactions. a. 5 b. 7 c. 9 d. 10 e. 12
Ans: b Response: See pages 183-184
16. It is a good idea to have the users role play the use cases as a way of confirming them during the analysis phase.
Ans: True Response: See page 193
39. A use case with seven unique transactions contributes ten unadjusted use-case points.
Ans: True Response: See pagen 184
7. Each use case describes _____ function(s) in which users interact with the system. a. one b. one or more c. many d. zero, one, or more e. all
Ans: a Response: See page 167
9. A(n) _____ use case is typically created early in the process of understanding the system requirements as a way of documenting basic information about the use case. a. overview b. detail c. essential d. real e. imaginary
Ans: a Response: See page 167
6. A scenario is the same as a(n) _____. a. use case b. relationship c. path through a use case d. collection of use cases e. role
Ans: c Response: See page 167
37. Setting the scope of the activity being modeled is a task that can be accomplished after completing the activity diagram.
Ans: False Response: See page 165
20. A use case that represents an important business process and involves the use of new technology would likely be given an importance level of medium.
Ans: False Response: See page 168
16. Erica has completed the use-case point analysis for the system she is building and found that it has 12 unadjusted actor weight points (UAW), 70 unadjusted use-case weight total (UUCW), a technical factor (Tfactor) of 15 and an environmental factor (Efactor) of 21. In computing this Efactor value Erica accounted for the fact that although she is very experienced, has top-notch technical skills, knows how to motivate her teams, her team for this project is partially staffed with part-timers who are not familiar with the system development process being used and who lack object-oriented experience. In other words, she has three environmental factors that count towards the person-hours multiplier (PHM). (a) How many person-hours will it take Erica to complete the project? (b) Next suppose that in addition to these three environmental difficulties, that she has two more strikes against her: the programming language being used is very difficult and the requirements are not stable. Should Erica rethink taking on this project? Explain.
Ans: Before anything else Erica first needs to compute the unadjusted use-case points (UUCP). UUCP is simply the sum of the UAW and the UUCW. In other words the UUCP equation is UUCP = UAW + UUCW. The values for UAW and UUCW are provided above. Plugging these values into the UUCP equation and computing, we find that the system has 82 unadjusted use-case points (UUCP). Next Erica needs to compute the adjusted use-case points (UCP). UCP is the product of UUCP, the technical complexity factor (TCF), and the environmental factor (EF). In other words the UCP equation is UCP = UUCP*TCF*EF. Erica has just computed the UUCP value. Unfortunately, she does not yet know the TCF and EF values. There are formulas for each: TCF = 0.6 + (0.01*Tfactor) EF = 1.4 + (-0.03*Efactor) Since the Tfactor and Efactor values are provided, Erica can plug these into these formulas and find that TCF = 0.75 EF = 0.635 Then plugging these values into the UCP equation and computing we find that the system has a value of 33.3375 adjusted use-case points (UCP) Now that Erica knows the UCP, she can compute the number of person-hours. The equation states that this is simply the product of the UCP and person-hours multiplier (PHM). In other words the conversion formula is Effort = PHM*UCP. We can now answer parts (a) and (b) a. Normally, when there are two or less environmental factors working against the timely delivery of the project, the PHM is taken to be 20 person-hours per adjusted use-case point. However, Erica has three strikes against her and must use a PHM value of 28: Effort = 33.3375*28 = 666.75 person-hours (since this is only an estimate, it makes sense to round this number to 670) b. Yes. Rethink it Erica. The rule of thumb is that if you have five or more environmental factors working against you, you need to rethink whether to take on the project. Here you have five. Maybe hire the part-timers to work full time, or get part-timers with more experience, or limit the scope of the project so the requirements are more stable. Without some adjustments, this project is too risky. You might never complete it. Response: See pages 182-187
10. Draw a sketch of the diagramming symbol for each of the following components of a use-case diagram. • Actor • Use case • Subject boundary • Association relationship • Include relationship • Extend relationship • Generalization relationship
Actor Use case Subject boundary Association relationship * * Include relationship <<include>> Extend relationship <<extend>> Generalization relationship Response: See page 174
22. The use case Take Order has a temporal trigger if it begins when a customer calls to place an order.
Ans: False Response: See page 170
6. The include relationship represents the optional inclusion of another use case.
Ans: False Response: See page 170
18. Rectangles are used to represent association relationships in use case diagrams.
Ans: False Response: See page 174
29. The first step in creating use case diagrams is to identify the primary actors and their goals.
Ans: False Response: See page 178
26. Use cases are typically written to document the normal flow of events. Exceptions that occur in the normal flow need not be documented as part of the use case description.
Ans: False Response: See pages 193
7. Explain the difference between normal flows and sub-flows that would be documented in a use case.
Ans: The normal flow of events describes the steps that are normally executed in a use case. The steps in a normal flow are listed in the order in which they are performed. In some cases it is recommended that the steps in a normal flow be decomposed to simplify the normal flow. Thus, subflows are used to help keep the normal flow of events as simple as possible. Subflows represent the decomposition of normal flow steps. At times, subflows could be replaced with a separate use case, if it makes sense. Response: See pages 170-171
42. To compute the adjusted use-case points (UCP), the unadjusted use-case points weight total (UUCW) is multiplied by the technical complexity factor (TCF) and the environmental complexity factor (ECF).
Ans: True
21. A use case that begins at the end of the month has a temporal trigger.
Ans: True Response: See page 170
12. An include relationship is modeled in a use case diagram by an arrow with the word <<include>> above it.
Ans: True Response: See page 174
40. A use case with eight unique transactions contributes fifteen unadjusted use-case points.
Ans: True Response: See pagen 184
18. The correct sequence of the major steps in creating use case diagrams is _____. a. identify the major use cases, expand the major use cases, confirm the major use cases, create the use-case diagram b. identify the major use cases, expand the major use cases, create the use-case diagram, confirm the major use cases c. create the use-case diagram, identify the major use cases, expand the major use cases, confirm the major use cases d. create the use-case diagram, identify the major use cases, confirm the major use cases, expand the major use cases e. identify the major use cases, confirm the major use cases, expand the major use cases, create the use-case diagram
Ans: a Response: See page 178
12. The event that causes a use case to begin is called a(n) _____. a. action b. trigger c. hammer d. anvil e. stakeholder
Ans: b Response: See page 170
14. Which of the following relationships represent the extension of the functionality of the use case to cover optional behavior? a. association relationship b. extend relationship c. include relationship d. generalization relationship e. optional relationship
Ans: b Response: See page 170
17. If a use case becomes too complex, it should be _____. a. rewritten to simplify it b. decomposed into a set of use cases c. written with a series of repeating steps to simplify it d. written from the perspective of an independent observe to simplify it e. dropped from the system, as it will be too complex to implement in the final system
Ans: b Response: See pages 172-173
10. The importance level of a use case increases for all of the following characteristics of the use case EXCEPT _____. a. the use case represents an important business process b. the use case supports revenue generation c. the technology is proven d. the functionality is complex e. the functionality is time-critical
Ans: c Response: See page 168
15. Which of the relationship types in use cases enables functional decomposition? a. association relationship b. extend relationship c. include relationship d. generalization relationship e. decompose relationship
Ans: c Response: See page 170
14. Describe the terms action, activity and object nodes that are found in an activity diagram.
Ans: Action is a simple non-decomposable piece of the overall behavior that is being modeled. On the other hand, an activity is used to represent a set of actions. An activity can further be decomposed into other activities or actions. Actions and activities can represent both computerized or manual behavior. They are depicted using rounded rectangles. Object nodes model objects in the activity diagram. They are represented using rectangles. Object nodes represent the flow of information from one activity to another activity. Response: See pages 160-162
34. Paths coming out of a decision node are always mutually-exclusive, while the paths coming out of a fork node are sometimes concurrent and sometimes mutually-exclusive.
Ans: False Response: See pages 162-163
24. A use case should be written from the perspective of at least one of the actors associated with the use case.
Ans: False Response: See pages 171-172
1. Use cases can be used to document both the current (As-Is) system and the future (To-Be) system.
Ans: True Response: See page 158
17. A formal way of representing how a business system interacts with its environment is termed a use case.
Ans: True Response: See page 158
35. Join nodes in an activity diagram are used to bring concurrent or parallel flows together back into a single flow.
Ans: True Response: See page 163
20. In estimating size and effort using use-case points, once the use-cases and use case diagram have been created, the actors and use cases must be classified as _____, _____, or ______. a. incremental, average, or radical b. small, average, or large c. simple, average, or complex d. discretionary, average, or urgent e. open, average, or closed
Ans: c Response: See page 182-183
8. Jim has documented a use case that describes the functionality of a system as "To compute gross pay, multiply the hours worked that are recorded on the time card from the time clock by the hourly rate that is recorded in the employee master file from the MS SQL server database." This is an example of a(n) _____ use case. a. overview b. detail c. essential d. real e. imaginary
Ans: d Response: See page 168
10. A very complex use case should be broken down into a set of use cases.
Ans: True Response: See page 172-173
11. An actor is represented in a use case diagram by a stick figure of a man.
Ans: True Response: See page 174
30. Object nodes in an activity diagram are depicted using rectangles.
Ans: True Response: See pages 160
19. When drawing the use-case diagram, an analyst should do the steps in this order: _____. a. draw the use cases on the diagram, identify the system boundary, place the actors on the diagram, and draw the lines connecting the actors to the use cases b. identify the system boundary, draw the use cases on the diagram, place the actors on the diagram, and draw the lines connecting the actors to the use cases c. place the actors on the diagram, draw the use cases on the diagram, identify the system boundary, and draw the lines connecting the actors to the use cases d. identify the system boundary, place the actors on the diagram, draw the use cases on the diagram, and draw the lines connecting the actors to the use cases e. none of the above gives the correct order of steps
Ans: b Response: See pages 181-182
12. What is an actor? What is their role in a system? Ans: An actor is a role played by an individual while they are interacting with the system, or it may be another system that interacts with the current system. An actor is not a specific person. Actors can provide input to the system, receive output from the system, or both. A primary actor is an actor who triggers the use case. Response: See page 173
13. Distinguish between logical models and physical models.
19. Each use case can be associated with one or more role(s) that users have in the system.
Ans: False Response: See pages 167
11. List and briefly describe the four major steps in writing effective use-case descriptions and use-case diagrams.
Ans: Identify the major use cases In this step you find the boundary of the system, identify the primary actors, list the goals for those actors, identify and write the overviews for the major use cases, and review any current use cases. Expand the major use cases In this step choose one of the use cases to expand, fill in the details, write the normal flow for the events in that use case, decompose the flow into subflows if needed, list the possible alternate or exceptional flows, and describe how the actor or system should react when an alternate or exceptional flow occurs. Confirm the major use cases Review the set of use cases, and revise as needed, and then start at the top again. Create the use-case diagram Draw the system boundary, place the use cases on the diagram, place the actors on the diagram, and then draw the associations. Revise as needed. Response: See page 178
8. Explain the usefulness of alternate flows and when they are used.
Ans: Alternate or exceptional flows are those that can happen, but they are not the normal flow. They are documented separately to keep the normal flow of events as simple as possible. For example, in a student registration system, you may have alternate flows for students with financial or academic holds on registration, or those who have to deal with a closed class situation before they can complete their registration. Response: See page 171
6. Distinguish between the association and generalization relationships in use case diagrams. When would you use each of these relationships?
Ans: An association relationship documents the communication between the use case and the actors that use the use case. All actors involved in the use case will be documented with the association relationship. The generalization relationship allows use cases to support the concept of inheritance, since use cases can inherit the behaviors of other use cases. For example, Athlete Registration and New Student Registration can both have generalization relationships with Register for Classes, which would be used by the typical student. Response: See page 170
5. Distinguish between the extend and include relationships in use case diagrams. When would you use each of these relationships?
Ans: An extend relationship documents the extension of the functionality of the use case to incorporate optional behavior. For example, if the use case Register for Classes describes the registration process at your university, the use case Clear Financial Hold would only be executed for students who have financial holds on their registration, and the relationship between these two use cases would be an extend relationship. An include relationship represents the mandatory inclusion of another use case, which would happen if you had decomposed a particularly complex use case into several simpler ones. The text points out that this type of relationship allows for functional decomposition. Response: See page 170
15. Distinguish between control flows and object flows in an activity diagram.
Ans: Control flows model the paths of execution through a business process. Control flows can only be attached to actions or activities, and are depicted using a solid line with an arrowhead depicting the direction of flow. Object flows model the flow of objects through the business process. Since activities or actions modify or transform objects, object flows are necessary to show the actual objects that are used by and modified by these actions and activities. Object flows are depicted using dashed lines with arrows, and must have an activity at one end and an object at the other end. Response: See page 162
31. Control flows in an activity diagram show the flow of objects into and out of activities.
Ans: False Response: See page 162
3. An essential use case describes the specific set of steps to be followed.
Ans: False Response: See page 168
41. To compute the adjusted use-case points (UCP), the unadjusted use-case points weight total (UUCW) is multiplied by the technical complexity factor (TCF), the environmental complexity factor (ECF), and the business-impact factor (BIF).
Ans: False Response: See page 183-184
38. The value of the unadjusted use-case points weight total (UUCW) is the sum of the number of unique transactions in each of the use cases.
Ans: False Response: See page 184
9. What is the SVDPI form for steps in a use case, and why is it important to use this format when writing use cases? Provide an example of a sentence written in this format.
Ans: SVDPI represents Subject-Verb-Direct Object and optionally Preposition-Indirect Object. This form of the sentence is useful for identifying classes and operations from the use case description. An example may be something like "The Student contacts the academic department to obtain a closed-class waiver." Response: See page 172
4. What are the five characteristics of a use case that impacts its importance level? Describe each, and indicate what conditions would result in a higher importance level.
Ans: The use case may represent an important business process, which results in a higher importance level. The use case may support the generation of revenue or cost reduction. If so, this would result in a higher importance level. If the technology needed to support the use case is new or risky, that will result in a higher importance level. If the functionality in the use case is complex, risky, and/or time-critical, then the importance level will be higher. If the use case could help increase the level of understanding of the evolving design of the system, and this increase in understanding comes with little relative effort, then the importance level will be higher. Response: See pages 168-169
1. Write a complete use case description for the interaction that a student would have with your college or university's class registration system.
Ans: There is no single correct answer to this question, as it will depend on the particular details of your school's system. Also, it may vary based on the student's perspective on the system. For example, at most schools athletes go through a different registration process than the rest of the students. This use case description, though, should document the following to be correct: • Use case name • Primary actor • Use case type • Stakeholders and interests • Brief description • Trigger • Relationships • Normal flow of events • Alternate/exceptional flows (this should include closed classes or others where special permits may be needed, holds on registration because of uncleared financial situations, etc.) Response: See pages 166-173
36. A guard condition represents the value of the decision-test, based on which a particular path from the decision node will be traversed.
Ans: True Response: See page 162
2. Use cases are the primary drivers for all of the UML diagramming techniques.
Ans: True Response: See page 167
4. A use case that describes functionality that is complex and risky would be given a high importance level.
Ans: True Response: See page 168
23. As Felix is documenting an order entry system, he discovers that someone can call up to place an order that is not a customer. In this case, the Take Order use case will use the Create Customer use case to capture the customer information, and then the order will be taken. This is an example of the extend relationship between use cases.
Ans: True Response: See page 170
9. The SVDPI form of sentences in use cases aids in the identification of classes.
Ans: True Response: See page 172
33. A decision node in an activity diagram is used to represent the actual test condition that is used to determine which of the paths exiting the node is to be traversed.
Ans: True Response: See pages 162-
3. What are the four types of use cases? When are each used?
Ans: Use cases will vary based on the purpose of the use case and the level of detail they contain. Thus, there will be overview versus detail use cases, and essential versus real ones. Overview use cases allow the analyst and the user to agree on a high-level overview of the requirements. This use case will only document information such as the name, ID number, primary actor, type, and a brief description. Detail use cases will document all of the information for the use case. These will be developed after all of the overview use cases have been agreed to by the users and the analysts. An essential use case describes only the minimum information necessary to understand the required functionality of the system. A real use case goes beyond the essential use case and describes the specific set of steps required to understand the functionality of the system. Essential use cases are implementation independent whereas real use cases are detailed descriptions of how to use the system once it is implemented. Response: See pages 167-168
A(n) _____ is a formal way of representing how a business system interacts with its environment. a. use case b. physical model c. relationship d. system boundary e. trigger
Ans: a Response: See page 158
11. The _____ relationship in use cases allows use cases to support the concept of inheritance. a. association b. extend c. include d. generalization e. none of the above
Ans: d Response: See page 170
21. A(n) ___________ actor is a separate system that interacts with the current system using standard communication protocols, such as TCP/IP, FTP, or HTTP, or an external database that can be accessed using standard SQL. a. incremental b. simple c. open d. average e. complex
Ans: d Response: See page 182
16. Individual steps in a use case should be written in the form _____. a. Direct Object, Verb, Subject, Preposition, Indirect Object b. Direct Object, Subject, Verb, Preposition, Indirect Object c. Subject, Verb, Preposition, Indirect Object, Direct Object d. Subject, Verb, Indirect Object, Preposition, Direct Object e. Subject, Verb, Direct Object, Preposition, Indirect Object
Ans: e Response: See page 172
Ans: Logical models are models that describe the business domain's activities witho
ut suggesting how they are conducted. Logical models are also referred to as problem domain models. Examples of logical models include activity diagrams and use case diagrams. Logical models are constructed in the analysis phase while physical models are constructed in the design phase. In the design phase, logical models are refined into physical models, which provide information that is ultimately used to build the system. Logical models allow the analyst to focus on the business operations without getting distracted by the implementation details. Response: See pages 158-159