Use case diagram

A use case diagram at its simplest is a representation of a user's interaction with the system that shows the relationship between the user and the different use cases in which the user is involved.

In the Unified Modeling Language, the relationships between use cases and actors are represented in use case diagrams originally based upon Ivar Jacobson's Objectory notation.

Consider modeling an automotive system: with SysML one can use Requirement diagrams to efficiently capture functional, performance, and interface requirements, whereas with UML one is subject to the limitations of use case diagrams to define high-level functional requirements.

Due to their simplistic nature, use case diagrams can be a good communication tool for stakeholders.

Common processes undertaken in this phase include the creation of use case diagrams, conceptual diagrams (class diagrams with only basic notation) and package diagrams (architectural diagrams).

CaseComplete provides the ability to edit the textual portion of use cases and requirements in a guided environment and the ability to create various types of diagrams including use case diagrams, wireframes of graphical user interfaces, and flowcharts.

Use case analysis is a technique used to identify the requirements of a system (normally associated with software/process design) and the information used to both define processes used and classes (which are a collection of actors and processes) which will be used both in the use case diagram and the overall use case in the development or redesign of a software system or program.

Communication diagrams represent a combination of information taken from Class, Sequence, and Use Case Diagrams describing both the static structure and dynamic behavior of a system.

UML's use case diagram provides a simple goal modeling notation.

These include use case diagrams, activity diagrams and sequence diagrams.

The level of abstraction of a use case model makes it an appropriate starting point for design activities, thanks to the use of UML use case diagrams and the end user's or domain expert's language.

Generalization can only be shown on class diagrams and on use case diagrams.

(In a UML use case diagram, they would be drawn as extended or included use cases, which are related to one or more primary use cases.)