State Machines

Estudies4you
UML State Machines-OOAD Lecture Notes
Introduction 
State Machines 
State machines indicate the sequences of states an object undergoes in response to events throughout its lifetime 
State machines are used to model 
  • the behavior of an individual object 
  • the dynamic aspects of a system 
State machines can visualize by,
  • highlighting the flow control from activity to activity 
  • highlighting the potential states of objects and the transition among those states
cse study zone,cse studies4you,estudies4you,State Machines in uml,uml State Machines,introduction to State Machines in uml,introduction to State Machines in ooad,define State Machine in uml,types of State Machines in uml,state chart diagram in uml,transition parts in uml,

Statechart Diagram 
  • Shows a state machine, emphasizing the flow of control from state to state 
  • Statechart diagram is used to model 
dynamic aspects of a system 
the behavior of reactive objects 
  • Important for constructing executable systems through forward and reverse engineering
cse study zone,cse studies4you,estudies4you,State Machines in uml,uml State Machines,introduction to State Machines in uml,introduction to State Machines in ooad,define State Machine in uml,types of State Machines in uml,state chart diagram in uml,transition parts in uml,

cse study zone,cse studies4you,estudies4you,State Machines in uml,uml State Machines,introduction to State Machines in uml,introduction to State Machines in ooad,define State Machine in uml,types of State Machines in uml,state chart diagram in uml,transition parts in uml,

A state machine refers to a behavior that recognizes the sequence of states an object undergoes in response to events throughout its lifetime.
A state refers to a situation of an object, where it satisfies some conditions, carries out some activity, or waits for some event. 

Name 
  • A textual string 
Entry/Exit actions 
  • Actions executed on entering and exiting the state 
cse study zone,cse studies4you,estudies4you,State Machines in uml,uml State Machines,introduction to State Machines in uml,introduction to State Machines in ooad,define State Machine in uml,types of State Machines in uml,state chart diagram in uml,transition parts in uml,

Internal transitions 
  • Transitions that are handled without causing a change in state 
Substates 
  • The nested structure of a state 
Deferred events 
  • A list of events that are not handled in that state, but are postponed and queued for handling by the object in another state 
Initial and final states 
  • Initial state shows the beginning of the state machine and final state shows the ending of the state machine
Transitions 
  • A transition is a relationship between two states 
  • An object performs certain actions in the first state. It then enters the second state when specified events happen and specified conditions are satisfied 
cse study zone,cse studies4you,estudies4you,State Machines in uml,uml State Machines,introduction to State Machines in uml,introduction to State Machines in ooad,define State Machine in uml,types of State Machines in uml,state chart diagram in uml,transition parts in uml,

The parts of transition are: 
Source state: State affected by transition 
Event trigger:  Event whose reception by the object in the source state makes the transition eligible to fire
Guard condition: A Boolean expression that is evaluated when the transition is triggered by the reception of event trigger
Effect: It is a behavior which executes when a transition fires
Action: State that is active after the completion of transition
Target state: An executable atomic computation 

Tags
To Top