Understanding Use Case Diagrams in Systems Analysis & Design

1. Asper School of Business University of Manitoba Systems Analysis & Design Instructor: Bob Travica Analyzing system processes:Use Case Diagram 1/2Updated 2018

2. Outline • The use case concept • Business events and systems • Elements of use case diagram • Reading use case diagrams • Creating use case diagrams 3510 Systems Analysis & Design * Bob Travica

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

4. Use case diagram in system documentation • Use Case helps to model system requirements • May be easier for users to understand than other diagrams 3510 Systems Analysis & Design * Bob Travica

5. Business Event concept • A stimulus that requires a system’s response • Delineated in time; stands on its own External events occur outside the system Temporal Events “clerk calls up customer account” Figure 5-2 Events affecting a payment system that determine what system has to do – functions, use cases

6. Event types • External Events (outside an IS) • Caused by external agent (human, system) • Temporal Events (inside an IS) • Occur at a certain point in calendar time • State Events (inside an IS) • Changes in system states, such as data Event: QuantityOnHand =< ReorderAmount (QOH goes under a min.) System’s response: Create new purchase order • Internal events - logic of automated decisions 3510 Systems Analysis & Design * Bob Travica

7. Figure 5-10 Events Table Input Output 3510 Systems Analysis & Design * Bob Travica

8. Elements of use case diagram:Actor and System • Actor is someone interacting with use case (system function). Named by a noun. • Similar to the concept of user, but • can be non-human and • a user can play different roles; (e.g.,: an employee can be worker and manager – plays 2 roles in a system1). (c) The same use case can have more actors.2 Name System • System • Shape of oval, contains small ovals that • stand for use cases (system functions) 3510 Systems Analysis & Design * Bob Travica

9. Actor-System relationship • Actor triggers (initiates, starts) use case (a system function); acts as the source of business event. • Actor has responsibility toward the system (inputs), and Actor has expectations from the system (outputs). • System has responsibility to respond properly to events – to execute an appropriate function. 3510 Systems Analysis & Design * Bob Travica

10. = Use Case Elements of use case diagram:Use Case • System function (process – automated or manual). Named by a verb. Do something • Each Actor must be linked to a UC, while some use cases may not be linked to actors (e.g., functions responding to temporal events, UC related to another UC). 3510 Systems Analysis & Design * Bob Travica

11. Connection between Actor and Use Case Boundary of a system Elements of use case diagram:Other components

12. Reading use case diagrams ONLINE BOOKSTORE INVETORY MANAGEMENT SYSTEM 3510 Systems Analysis & Design * Bob Travica

13. How to create use case diagram 1. List main system functions (use cases) in a column: • think of business events demanding system’s response • users’ goals/needs to be accomplished via the system • Create, Read, Update, Delete (CRUD) & other tasks • Naming use cases – user’s needs usually can be translated in data tasks 2. Draw ovals around the function labels (use cases) 3. Draw system boundary 4. Draw actors and connect them with use cases (if more intuitive, this can be done as step 2) • Exercise Continues with slides set #2 3510 Systems Analysis & Design * Bob Travica