  Use cases as textual visual modeling techniques have become a key construct
and the foundation of the most popular de facto standard technique for
performing software requirements analysis and specification. This paper
describes use cases in terms of a recently proposed model, the thinging machine
(TM) model. Such a link to TM strengthens the notion of use cases and clarifies
related concepts. For example, the concept of events is utilized in an
unconstrained way in use cases, and TM may contribute in this direction.
Several selected use cases are remodeled using TM. This study provides many
insights. For example, one result shows that use cases are an activation
apparatus of mega-triggering (high-level events) wherein a group of submachines
(processes) are actuated.
