The State Diagrams

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The State Diagrams

• Presentation prepared by
• Daniel Sadowski
• Jarek Socha
• Tutor Mariusz Trzaska, PhD
• PJWSTK 2006

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The State Diagram

• Addition to the Class Diagram
• Represents all states an object can have and the
  transitions between them
• Relates to the finite automat
• Created for classes, which have well defined
  states that influence their behaviour

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The State Diagram II

• Complete diagram is a set of subdiagrams, which
  communicate with each other using events
• One classs state diagram can refer to another
  classs state
• Useful for showing the life cycle of a class

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State Diagram in UML

• UML State representation

entry/ action/ action/ ... do/ activity/
activity/... exit/ action/ action/ ...
State Name
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State Diagrams in UML

• Action an operation which cannot be stopped
• List of actions treated as a single action
• Activity an operation which can be stopped
• List of activities treated as a single activity
• Entry keyword defining operations taking place
  after entering the state
• Do operations happening when the state is
  active
• Exit keyword defining operations taking place
  when exiting the state

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State types

• Simple a state without a substructure
• Sequential composite state consists of one or
  more substates. Only one of them is active when
  the compisite state is active

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State types II

• Concurent composite state divided into at least
  two concurent substates, which are active at the
  same time when the composite state is active!

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State types III

• Initial state pseudostate used to indicate the
  starting point of an objects life cycle!
• Final state pseudostate used to indicate the
  final point of an objects life cycle!

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State types IV

• Junction state pseudostate connecting chain of
  transitions into one.
• History state pseudostate, which activates a
  previously active state.

H
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State types V

• Submachine reference state pseudostate to which
  there is a reference on the diagram, switched by
  a state specified in the reference

include S
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State types VI

• Stub state (PNIOK) pseudostate to which theres
  a reference on a diagram, which is a part of
  another composite state.

S
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Events 0001

• Happen in one point in time
• Worth analysing from the project designs
  perspective
• Can be sorted in time

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Events 0010

• Calling object receives a synchronized
  operation execution order. Most basic kind of
  event.
• op(a T)
• Change satisfies a boolean condition. Such an
  event is useful for modelling situations when an
  object changes its state after receiving an
  answer to a message it sent.
• when(expression)

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Events 0011

• Signal an asynchronic operation execution
  order. Useful in modelling events coming from
  outside of the system
• name_sig(a T)
• Time ammount of time elapsed
• after (time)

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Actions 0xf6660001

• Assigment assigns a value to a variable
• variable expression
• Call calls an operation on an object. Can
  return a value.
• name (argh1, argh2, ...)
• Create creates a new object (surprise!)
• new name_of_class (argh1, ...)

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Actions 0xf6660002

• Destroy deletion of an object
• destroy()
• Send creates a signal and sends it to the
  object(s)
• name_signal(argh1, argh2, ...)
• Terminate objects so-called suicide
• terminate

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Actions 0xf6660003

• Return specifies a return value
• return value

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Transitions

• Can be defined by an event that called it,
  condition and action, which is called before the
  state change.
• Therere four types of transitions.

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Types of transitions

• External transition
• Internal transition
• Selftransition
• Completion transition

event condition /action
condition /action
State 1
state 2
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Examples class GUARD
Getting bored
RUNNING TOWARDS MOVEMENT
Friend detection
Movement detection
CHATTING
Detecting enemy / attacking
Finishing looting nothing to loot cant hold
anything more / setting the body on fire
Killing enemy
LOOTING BODY
FIGHTING
WALKING AROUND
Feeling safe again
Losing battle healthlt10
RUNNING AWAY
DYING PAINFULLY
Failing to run away health0
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EXAMPLE concurent composite state
replacment of oil filter
Oil change
Changing the tires
Checking the tires