ISMT221 Information Systems Analysis and Design Use case diagram Lab 4 Tony Tam

Role of Software Engineering Focusing on the result to achieve (deliverables) Realization of the need and the desire to learn the business (analysis and design) Gratification of solving a worth-while problem (successful SDLC) To success, we need precise conceptualization and specification

Use Case Modeling Use cases Drive activities performed within the process (features), and the activities that happen next (successors) As common language (narrative text) for all people Use case model A collection of use cases and actors, describing the composite behavior of a system Use case diagram Provide high-level visual representation of actors, use cases and their relationships

Balancing Use Case Model Risks Use cases are too functional instead of object- oriented Too many use cases may result in deviation of understanding Inconsistent or undefined system boundary Balancing activities for analysis Use Case Modeling (what features?) Domain Analysis (who involved?) Interface Specification (interaction?) Architecture definition (how to support?)

Elements of use case diagram

Actor External entities representing users, systems, and other elements interacting with the system An actor is a role, not a specific person Not Peter, Paul and Mary Actor could be: person, external system, device, outside organization Personality Type Behavior InitiatorInitiates the use case External serverProvides a service to the system in the use case ReceiverReceives information from the use case FacilitatorSupports another actor's interaction with the system

Use Case A description of a set of sequences of actions performed in a system yielding an observable result to actor Collection of Use Cases are grouped into package; a package can be used to refer to a set of use cases (to avoid overcrowding)

System Boundary Limits of the system and contains the use cases Actors are outside system boundary (external) Use cases are inside system boundary (internal) e.g. employee payroll system (system boundary) HSBC Hexagon (external payment) – actor Employee (customer) – actor Pay monthly compensation – use case

Relationships Association – communicates between actor and use case (Visio only provides unidirectional association) e.g. account clerk communicates generate report Include – one use case uses the behavior of another use case e.g. pay over time uses calculate workhour Extend – one use case extends behavior of another use case to add behavior e.g. pay over time extends pay regular time