Chapter 3 : Use Cases

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Use cases
Jo Hart
Flashcards by Jo Hart, updated more than 1 year ago
Jo Hart
Created by Jo Hart over 9 years ago
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Question Answer
use case – an activity that the system performs, usually in response to a request by a user
user goal technique – a technique to identify use cases by determining what specific goals or objectives must be completed by a user
event decomposition technique – a technique to identify use cases by determining the external business events to which the system must respond
elementary business processes (EBPs) – the most fundamental tasks in a business process, which leaves the system and data in a quiescent state; usually performed by one person in response to a business event
event – something that occurs at a specific time and place, can be precisely identified, and must be remembered by the system
external event – an event that occurs outside the system, usually initiated by an external agent
actor – an external agent; a person or group that interacts with the system by supplying or receiving data
temporal event – an event that occurs as a result of reaching a point in time
CRUD technique – an acronym for Create, Read/Report, Update, and Delete; a technique to validate or refine use cases
brief use case description – an often one-sentence description that provides a quick overview of a use case
use case diagram – the UML model used to graphically show use cases and their relationships to actors
automation boundary – the boundary between the computerized portion of the application and the users who operate the application but are part of the total system
«includes» relationship – a relationship between use cases in which one use case is stereotypically included within the other use case
What is the best or most useful way to use the CRUD technique? CRUD is best used as a check or validation of existing use cases. When CRUD is used to identify use cases, often the use cases are too low level and do not reflect the business processes nor the user goals.
What does a CRUD matrix or table show? A CRUD table shows the data entities or domain classes across the top, with a list of the use cases along the right side. Those use cases that either create, report, update, or delete the particular data entity are noted in the cells of the table.
What is the most common way to organize use cases? By user or if a larger grouping is desire, by department.
What are the three component part of a use case diagram and what do they represent? An oval represents the use case. A stick figure represents an actor. A straight line represents a relationship between an actor and an use case. A rectangle represents the automation boundary.
What does an “includes” relationship mean? And how is it represented? The “includes” relationship means that one use case will use the services of another use case, hence the second use case is “included within” the first use case. It is represented by a dashed lined with an arrow. The arrow points to the “included” use case, i. e. “use case A includes use case B.”
What is the primary source of use cases in the user goal technique? An interview with the user.
What is the difference between a state event and a temporal event? Both are internal events, but a state event is triggered by a change in the “state” of the system (or data in the system, and a temporal event is trigger purely by the passage of time.
How do you identify the scope of an event, i. e. what is part of the event and what is not? The primary identifier is if the system can go into a quiescent state after the end of the event. When a transaction (an event) is completed, all the data has been updated and the system can wait for another transaction to occur.
Why don't we include technology dependent events such as logging onto a system? What is the assumption that we make? The assumption is the perfect technology assumption. We don't include technology dependent events during analysis because they tend to confuse user requirements, e.g. problem domain issues, with technology issues, which are system design issues.
What are the five activities of systems analysis? The five activities of systems analysis are: 1. Gather detailed information 2. Define requirements 3. Prioritize requirements 4. Develop user-interface dialogs 5. Evaluate requirements with users
What is a use case? A use case is an activity that the system performs as a result of some event or action by a user.
What are the two techniques used to identify use cases? User goal technique and the event decomposition technique
Describe the user goal technique for identifying use cases. The user goal technique is done by interviewing a user (or user role) to see what their work “goals” or objectives are. These are low level objectives to accomplish a piece of work or to complete a work procedure. The system then must have use cases to support each user goal.
What are some examples of users with different functional roles and at different operational levels? Functional roles may be like department organization such as shipping, or sales, or accounting. Different operational level may be like clerks, or middle management like supervisors, and then executives.
What are some examples of use case names that correspond to your goals as a student going through the college registration process? Be sure to use the verb-noun naming convention.  Find a course and section  Register for a section of a course  Cancel a registration
What is the overarching objective of asking users about their specific goals? To discover and document every user case that the system must support.
How many types of users can have the same user goals for using the system? No real limit. Users from different departments can access the same use cases, e.g. can have the same user goal for using the system.
Describe the event decomposition technique for identifying use cases. Look at all of the business processes that result in some type of business event. The business events are triggers that require system processing, e.g. that require use cases.
Why is the event decomposition technique considered more comprehensive than the user goal technique? Event decomposition not only looks at user initiated events (the same as the user goal technique), but it also considers temporal events and state events. Hence it is more comprehensive.
What is an elementary business process (EBP)? An EBP is a fundamental business process that may input data and receive information, but upon completion of the EBP the system has finished processing and can enter a quiescent state ready for a new event.
Explain how the event decomposition technique helps identify use cases at the right level of analysis. Since event decomposition depends on EBP, then it automatically arrives at the right level of analysis. EBP, where the system has finished a complete transaction, is the same level that is required for a use case definition.
What is an event? Something that occurs at a specific time and place. It can be identified, and for purposes of systems analysis, the system must recognize it and capture some information from it or about it.
What are the three types of events? External event – usually from a user Temporal event – occurs at a point in time, or due to a time interval State event – a change of state or condition of some data within the system
Define an external event and then give an example that applies to a checking account system. An external event is something that occurs external to the system, and is trigger by a user action. An example might be that a user makes a direct deposit to his/her account.
Define a temporal event and then give an example that applies to a checking account system. A temporal event is one that occurs at a point in time. An example might be that at the end of the month interest (or monthly checking account fee) is calculated and credited to the account.
What are system controls, and why are they not considered part of the users’ functional requirements? System controls are safety procedures or mechanisms that protect the system and the data. They are not part of the users' functional requirements because the users normally do not initiate nor activate these controls. They must exist above and overriding the external events. These controls are not normally part of the users' work processes.
What is the perfect technology assumption? It assumes that technology will work perfectly and that in the early stages of systems analysis we do not worry about such things as security, logging in, database backup, etc. Those issues are addressed after the initial functional requirements are determined.
What are three examples of events that are system controls in a typical information system that should not be included as a use case because of the perfect technology assumption? Backing up a database User logging onto the system Restoring the database
What are the four operations that make up the CRUD acronym? C = Create R = Read or Report (output) U = Update D = Delete
What is the main purpose of using the CRUD technique? The CRUD technique is a good way to validate the use cases that have been identified using the user goal and event decomposition techniques. It is a double check to make sure the list of use cases covers all of the processes against the database. When it is used as the primary method to find use cases, the use cases often do not track the business procedures very well.
What is UML? UML stands for Unified Modeling Language, and it is the graphical modeling technique used to model object-oriented models. It is the industry standard for OO modeling.
What is the purpose of UML use case diagrams? Use case diagrams provide a graphical view of use cases and the actors that invoke those use cases. They provide a nice overview of use cases. They can organize use cases together in meaningful ways.
What is another name for “actor” in UML, and how is it represented on a use case diagram? An actor is also an external agent. In a use case diagram it is represented as a stick figure.
What is the automation boundary on a use case diagram, and how is it represented? The automation boundary is the boundary between the automated system, i.e. the application, and the external world, including the actors. It is represented by a rectangular boundary box.
How many actors can be related to a use case on a use case diagram? As many as necessary. All those that use that particular use case.
Why might a systems analyst draw many different use case diagrams when reviewing use cases with end users? An analyst will draw different use case diagrams to organize the use cases in different ways to illustrate different subsystems, or departments, or work associations.
What is the «includes» relationship between two use cases? The «includes» relationship is where one use case effectively uses the services of another use case. It is as though one use case were embedded within another use case.
Think about a university course registration system. What is an example of an event of each type? Name each event by using the guidelines for naming an external event. 1. External agent wants something – Student registers for a section of a course 2. External agent wants some information – Student searches for a course 3. Data changed and needs to be updated – Instructor assigned to teach a course section 4. Management wants some information – Show enrollments for all courses in a department
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