Chapter 10 - Modeling Event-Based Behavior with State Machines

Abstract

This chapter describes how to model behavior in terms of the response of blocks to internal and external events, using state machines. State machines are used to describe behavior of a block in terms of its states and transitions. State machines can be composed hierarchically, like other SysML behavioral constructs, enabling arbitrarily complex representations of state-based behavior. A state machine describes a potentially reusable definition of the state-dependent behavior of a block. Each state machine is described using a state machine diagram. Each state machine contains at least one region, which itself can contain a number of substates, pseudostates (called collectively vertices), and transitions between those vertices. During execution of a state machine, each of its regions has a single active state that determines the transitions that are currently viable in that region. A region can have an initial pseudostate and final state that correspond to its beginning and completion, respectively.