UML-State-Diagrams

Introduction

In the Unified Modeling Language (UML), a state machine diagram models the behaviour of a single object, specifying the sequence of events that an object goes through during its lifetime in response to events. The primary focus of the state machine diagram is to depict the states of a system. These states are essential while drawing a state transition diagram.

State Machine Elements:

• States: States represent the conditions or situations that a system can be in at any given time. It is denoted by a round-cornered rectangle.
• Transitions: Transitions represent the changes from one state to another in response to an input. It are denoted by lines with arrowheads.
• Inputs: Inputs represent the events or conditions that trigger a transition from one state to another.
• Decision box: Outputs represent the actions or results that occur when a transition is made.
• Initial State: the system starts before any inputs are received, it is denoted by a filled black circle.
• Final State: the system transitions to when it has completed its task. It is denoted by a circle with a dot inside.

UML State machine diagram is used for:

• modelling the object states of a system
• pinpointing the events responsible for state transitions
• Specifying the context and requirements of a system
• Modeling the basic flow of events in a use case

Guidelines be considered while drawing a state chart diagram:

• The name of a state transition must be unique.
• The name of a state must be easily understandable and describe the behaviour of a state.
• If there are multiple objects, then only essential objects should be implemented.
• Proper names for each transition and event must be given.