Statechart Diagrams

A statechart diagram shows a state machine, focusing on the flow of control from state to state. A state machine is a behavior that specifies the sequences of states an object goes through during its lifetime in response to events, together with its responses to those events.

Common Properties

A statechart diagram is a special kind of diagram and shares the same common properties as do all other diagrams like a name and graphical contents that are a projection into a model. What distinguishes a state chart diagram from other diagrams is its content.

Content

Statechart diagrams commonly contain:

• Simple states and composite states
• Transitions including events and actions

Common Uses

When we model the dynamic aspects of a system, a class or a use case, we will use statechart diagrams in one way:

• To model reactive (event-driven) objects.

Common Modeling Techniques

Modeling Reactive Objects

To model a reactive object:

• Choose the context for the state machine, whether it is a class, a use case or the system as a whole.
• Choose the initial and final states for the object.
• Decide on the stable states of the object. Start with the high-level states of the object and only then consider its possible substates.
• Decide on the meaningful partial ordering of stable states over the lifetime of the object.
• Decide on the events that may trigger a transition from state to state.
• Attach actions to these transitions and/or to these states.
• Consider ways to simplify your machine by using substates, branches, forks, joins and history states.
• Check that all states are reachable under some combination of events.
• Check that no state is a dead end.
• Trace through the state machine, either manually or by using tools, to check it against expected sequences of events and their responses.

Consider the following example:

Suryateja Pericherla

Suryateja Pericherla, at present is a Research Scholar (full-time Ph.D.) in the Dept. of Computer Science & Systems Engineering at Andhra University, Visakhapatnam. Previously worked as an Associate Professor in the Dept. of CSE at Vishnu Institute of Technology, India.

He has 11+ years of teaching experience and is an individual researcher whose research interests are Cloud Computing, Internet of Things, Computer Security, Network Security and Blockchain.

He is a member of professional societies like IEEE, ACM, CSI and ISCA. He published several research papers which are indexed by SCIE, WoS, Scopus, Springer and others.