Task: Structure the Use-Case Model |
Structure the use-case model to make the requirements easier to understand and to maintain. This includes leveraging commonality amongst use cases and actors, and identifying optional and exceptional behavior.
Disciplines: Requirements
Purpose
The purpose of this task is to: Extract behavior in use cases that need to be considered as abstract use cases. Examples of such behavior includes common behavior, optional behavior, exceptional behavior, and behavior that is to be developed in later iterations. Find new abstract actors that define roles that are shared by several actors.
Relationships
Roles | Primary Performer: Analyst | Additional Performers:
Inputs | Mandatory: Use-Case Model | Optional: None
Outputs | Use-Case Model
Steps
Identify Common Requirements
Understand the requirements that are common to more than one Use Case, or that describe optional or exceptional behavior. Review each completed use case and note any commonality or exceptiona behavior that's not tightly coupled with the rest of the use case.
Organize requirements in use cases
Move the identified requirements to more appropriate use cases to make understanding and managing the use cases easier. See Include Relationship and Extend Relationship to understand what kinds of relationships support structuring the use case model. See Defining Include Relationships and Defining Extend Relationships to understand how to organize and reference requirements within abstract use cases.
Establish Generalizations Between Actors
Model common characteristics between actors. Write a brief description of the actor-generalizations, and include them in use-case diagrams for further clarification. For more information, see Guideline: Using Actor Generalization.
Organize the Use-Case Model Content into Packages
If the use-case model has a large number of elements, you might want to consider organizing the use cases into use-case packages. See Guideline: Packaging Use Cases for more information on when to consider this option.
Evaluate Your Results
Discuss the incorporation of include-, and extend-relationships with the customer and the users, and assure they have a clear understanding of the system based on the updated use case model.
Alternatives
If it's difficult or awkward to represent common requirements by structuring the use case mode, consider moving common content into other requirements work products instead of refactoring the model.
More Information
Checklists | Use-Case Model
Concepts | Communicate Association Extend Relationship Include Relationship
Guidelines | Defining Extend Relationships Defining Include Relationships Using Actor Generalization
© Copyright IBM Corp. 1987, 2009. All Rights Reserved.