Asper School of Business University of Manitoba Systems Analysis & Design Instructor: Bob Travica Analyzing systems process: Use Case Diagram

3510 Systems Analysis & Design * Bob Travica2 Outline The use case concept Business events and systems Elements of use case diagram Include and Extend relationships between use cases Reading use case diagrams Creating use case diagrams

3 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. Figure 6-3 Use Case Diagram of Order-Entry Subsystem for RMO Use case

3510 Systems Analysis & Design * Bob Travica4 Use case diagram in system documentation Use Case helps to model system requirements Easy for users to understand

5 Business Event concept Figure 5-2 Events affecting a Charge Account Processing System that determine what system has to do – functions, use cases A stimulus that requires a system’s response Delineated in time; stands on its own

3510 Systems Analysis & Design * Bob Travica6 Event types External Events Caused by external agent (human, system) Temporal Events Occur when system reaches a point in time; time tacking in computer State Events Asynchronous events responding to system trigger (e.g., if inventory =< reorder amount, create purchasing order)

3510 Systems Analysis & Design * Bob Travica7 Events Table Figure 5-10

3510 Systems Analysis & Design * Bob Travica8 Elements of use case diagram: Actor Actor is someone interacting with use case. Noun. 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). Label

3510 Systems Analysis & Design * Bob Travica9 Elements of use case diagram: Use Case System function (process – automated or manual). Verb. Do something 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 Travica10 Elements of use case diagram: other Boundary of system; Automation Boundary > Include relationship between Use Cases (one UC must call another; e.g., Login UC includes User Authentication UC) > Extend relationship between Use Cases (one UC calls Another under certain condition; think of if-then decision points) Connection between Actor and Use Case

3510 Systems Analysis & Design * Bob Travica11 Extend relationship – linking an optional use case to a standard use case. Extend relationship 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 case can execute without the extend case  loose coupling.

3510 Systems Analysis & Design * Bob Travica12 Reading use case diagram with Extend relationship

3510 Systems Analysis & Design * Bob Travica13 Include relationship Include relationship – a standard case linked to an mandatory use case. Standard use case can NOT execute without the include case  tight coupling. 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).

3510 Systems Analysis & Design * Bob Travica14 Reading use case diagram with Include relationship

3510 Systems Analysis & Design * Bob Travica15 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