Use Case Diagram

The Use Case diagram is used to define and view Use Cases and the Actors that derive value from the system. The Use Case diagram describes the relationship between the Actors and the Use Cases, enclosing the Use Case within a Boundary that defines the border of the system; the Actors, by definition, lie outside the Boundary. While the Use Case diagram can appear simplistic, it is a powerful communication device that describes the value or goals that external roles obtain from interacting with the system. Each Use Case can be detailed with descriptions, constraints and any number of scenarios that contain sets of steps performed alternately by Actor and system to achieve the desired goal.

Elements

The main elements that can appear in Use Case diagrams are:

• Boundary
• Actor
• Use Case
• Scenario

The main connectors that can appear in Use Case diagrams are:

• Communication Path
• Generalization
• Includes
• Extends

Tools

There are a variety of tools available for working with Use Cases in addition to the Use Case diagram itself. These include:

• Scenario window - which provides a way of detailing the descriptions, constraints and the step of each scenario
• Documentation Generator - which allows corporate, reports or ad-hoc documentation to be created in a variety of formats, including docx, pdf and rtf
• Traceability - which provides a hierarchical view of an elements relationships to other model elements

• Responsibilities window - which provides a composite view of the important responsibilities of an element including Constraints, Requirements and Scenarios
• Relationship Matrix - which allows the connections between Requirement (or other elements) and other elements such as stakeholder needs to be visualized in a matrix

The main tool used for working with Use Cases is the Scenario window, which is a comprehensive and purpose built facility for working with Use Cases and Scenarios. The tool can be used to define the details of a Use Case and its scenarios and constraints, which provides a productive alternative to the traditional text-document based approach to defining Use Cases. This ensures that the Use Case diagram and the textual details of the Use Cases and its Scenarios and Constraints are all contained in the same model and can be traced.

If the Use Cases are required in a document format for contractual or process reasons, a Use Case Report can be generated automatically from the models using the in-built documentation engine.

Scenario Builder

Usage

The Use Case diagram can be used to define the details of a Use Case and its Scenarios and Constraints. This is a welcomed alternative to the traditional text-document based approach commonly used to define Use Cases. This ensures that the Use Case diagram and the textual details of the Use Cases and its Scenarios and Constraints are all contained in the same model and can be traced. If the Use Cases are required to be presented in a document format for contractual or process reasons, a Use Case Report can be generated automatically from the models using the in-built documentation engine.