Use cases are the UML vehicles for requirements description. Use cases have gained wide spread usage due to their ease of use, and their use of natural language to describe software behaviour from the point of view of the users.

The use case diagram, which many UML proponents seem to use is not informative enough for most requirements purposes. This is because despite the diagram showing actors and corresponding use cases, it does not outline the nature of interactions amongst those elements.

This is an application for authoring use case descriptions and their state-based information. The application animates the edited description to protototype described behaviour. The underlying motivation is that  when a description is animated rather than just read, users easily identify flaws in the behaviour represented by the description.