Asper School of Business University of Manitoba Systems Analysis & Design Instructor: Bob Travica Analyzing systems process: Use Case Diagram 3510 Systems Analysis & Design * Bob Travica
Outline The use case concept n Business events and systems n Elements of use case diagram n Include and Extend relationships between use cases n Reading use case diagrams n Creating use case diagrams n 3510 Systems Analysis & Design * Bob Travica 2
Use case concept • Use case is a model of system functionality. • Think of main functions a system performs for users – “cases” of using a system. Use case Use Case Diagram of Order-Entry Subsystem for RMO Figure 6 -3 3
Use case diagram in system documentation • Use Case helps to model system requirements • Easy for users to understand 3510 Systems Analysis & Design * Bob Travica 4
Business Event concept • A stimulus that requires a system’s response • Delineated in time; stands on its own Figure 5 -2 Events affecting a Charge Account Processing System that determine what system has to do – functions, use cases 5
Event types n External Events n n Temporal Events n n Caused by external agent (human, system) Occur when system reaches a point in time; time tacking in computer State Events n Asynchronous events responding to system trigger (e. g. , if inventory =< reorder amount, create purchasing order) 3510 Systems Analysis & Design * Bob Travica 6
Events Table Figure 5 -10 3510 Systems Analysis & Design * Bob Travica 7
Elements of use case diagram: Actor • Actor is someone interacting with use case. Noun. Label • Similar to the concept of user, a user can play different roles; (example: a prof. can be instructor and researcher – play 2 roles). • Actor triggers use case. • Actor has responsibility toward the system (inputs), and Actor have expectations from the system (outputs). 3510 Systems Analysis & Design * Bob Travica 8
Elements of use case diagram: Use Case Do something n n System function (process – automated or manual). Verb. Each Actor must be linked to a use case, while some use cases may not be linked to actors. = Use Case 3510 Systems Analysis & Design * Bob Travica 9
Elements of use case diagram: other Connection between Actor and Use Case Boundary of system; Automation Boundary <<include>> Include relationship between Use Cases (one UC must call another; e. g. , Login UC includes User Authentication UC) <<extend>> Extend relationship between Use Cases (one UC calls Another under certain condition; think of if-then decision points) 3510 Systems Analysis & Design * Bob Travica 10
Extend relationship • Extend relationship – linking an optional use case to a standard use case. • Example: Register Course (standard use case) may have Register for Special Class (extend use case). The optional UC extends the standard UC (use the verb to figure direction arrow). • Standard use can execute without the extend case loose coupling. 3510 Systems Analysis & Design * Bob Travica 11
Reading use case diagram with Extend relationship 3510 Systems Analysis & Design * Bob Travica 12
Include relationship • Include relationship – a standard case linked to an mandatory use case. • Example: to Authorize Car Loan (standard use case), a clerk must run Check Client’s Credit History (include use case). The standard UC includes the mandatory UC (use the verb to figure direction arrow). • Standard use can NOT execute without the include case tight coupling. 3510 Systems Analysis & Design * Bob Travica 13
Reading use case diagram with Include relationship 3510 Systems Analysis & Design * Bob Travica 14
How to create use case diagram 1. List main system functions (use cases) in a column (think of business events demanding system’s response; think of users’ goals to be accomplished via the system) 2. Draw ovals around the function labels 3. Draw system boundary 4. Draw actors and connect them with use cases (if more intuitive, this can be done as step 2) 5. Specify include and extend relationships between use cases 3510 Systems Analysis & Design * Bob Travica 15
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