IT7001_Week4_03-Modelling System Requirement with Use Cases (3).pdf

Introduction to Use-Case Modeling ▪ Challenges in a system development process ▪ How to gather system requirements ▪ How to specify system requirements in a way the ▪ ▪ user can understand How to verify and validate system requirements. Some models e.g. data and process models, are understood by de...

Introduction to Use-Case Modeling ▪ Challenges in a system development process ▪ How to gather system requirements ▪ How to specify system requirements in a way the ▪ ▪ user can understand How to verify and validate system requirements. Some models e.g. data and process models, are understood by developers but not by users. Use-Case Modeling ▪ Models business processes in terms of: ▪ Business events ▪ Triggers of business events ▪ System responses to business events ▪ Origins in object-oriented modeling ▪ Well accepted by non-object methodologies as a good communication tool with end users Benefits of Use-Case Modeling • • • • • • • • • • A tool for capturing functional requirements Helps to decompose a system scope into more manageable pieces A good communication tool with users and other stakeholders Helps to estimate a project scope, tasks and schedule A good starting point for defining test plans and test cases Provides a baseline for user help system, training manuals and system development documentation. Provides a tool for requirements traceability A good starting point to identify data objects Provides functional specifications for designing user and system interfaces Provides a means of defining database access requirements Use-Case Diagrams Use-Case Diagram ▪ Graphically depicts the interactions between the system and its actors ▪ Depicts the functionality of the system ▪ Defines the boundaries of the system Actor A person, an object, time, an organisation or another system which interact with the system to exchange information. Use case ▪ A behavior of the system that describes a single business task from an actor’s point of view. ▪ A function provided by the system as a set of events that yields a visible result to the actor. ▪ Initiated by an actor that access the functionality of the system or another use case Use Case Association Relationship A relationship that shows an interaction between an actor and a use case ▪ Modeled as a solid line ▪ An arrow-headed line touching the use case indicates that the use case was initiated by the actor. ▪ A line without arrows indicates a receiver actor. ▪ Associations may be bidirectional or unidirectional Objectives and Steps of Requirements Use-Case Modeling ▪ Objectives: ▪ ▪ Collect and analyse requirements free of implementation details Use the Use Case model as a communication tool ▪ Steps 1. Identify business actors (produce Actor Glossary) 2. Identify business use cases (produce Use Case Glossary) 3. Construct Use-Case Model diagram 4. Produce Use-Case narratives (high-level and fullydocumented) Step 1: Identify Business Actors Ask questions like: ▪ Who provides inputs to the system? ▪ Who receives outputs from the system? ▪ Is there a need for interfaces to other systems? ▪ Are there use cases triggered by time ? ▪ Who will maintain information in the system? Step 2: Identify Business Requirements Use Cases Ask questions like: ▪ What are the tasks performed by an actor? ▪ What information does the actor provide to the system? ▪ What information does the actor need from the system? ▪ Are there documents that can be used to discover use cases?