Artifact: Use-Case Model
This artifact captures a model of the intended functions and environment of the system and serves as a contract between the customer and the team.
Domains: Requirements

This artifact presents an overview of the intended behavior of the system. It is the basis for agreement between stakeholders and the project team in regards to the intended functionality of the system. It also guides various tasks in the software development lifecycle.

Impact of not havingWithout this artifact, it is difficult to determine all of the relationships between actors and use cases. It is also difficult to gain an understanding of how different use cases relate.
Reasons for not needing

You might not need this requirement if the overall set of use cases is small and has no complex relationships.

You also might not need a use-case model if you use an alternative approach to document functional requirements.

Representation Options

Representation options include reports and diagrams from UML modeling tools, graphical representations created by using drawing tools, and drawings on whiteboards. Most of the information in the use-case model is captured in the use-case specifications.

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