Unified Modeling Language UML State diagram Activity diagrams

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Unified Modeling Language UMLState diagram
Activity diagrams
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Grouping of diagrams structure, behavior,
implementation and usage
Structure
Implementation
Class Diagram Object Diagram
Package Diagram Component Diagram
Korisniki pogled

• Sequence
• Collaboration

Use Case Diagram
Statechart Activity Diagram
Deployment Diagram
Deployment
Behavior
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Grouping of diagrams by phases
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Notation in state diagrams and activity diagrams
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State diagrams (state machine)

• Describe dynamical behavior of isolated object in
  time, that detects events and react on them
• Example Click on remote control, change of the
  state of television set from on to other channel
• Event is called everything that influence an
  object
• State is set of values of an object (instance of
  a class) with the same response on the events
  that happens to it.
• Objects in the specific state react on the same
  way on specific event and do the same action

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State diagrams (1)

• State diagrams describe state of one object that
  is in transition from one to other state and
  shows start and end state
• State diagrams (state machines) beside states of
  objects describe also dynamical behavior of use
  case, operations, collaboration and methods.
• For all this elements, state is step in their
  deployment

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State diagrams (2)

• State diagram is graph in which nodes are states
  of one isolated object and arcs are transition
  from one to other state
• Outside effects are described with events
• Reaction depends of the state in which object is.
  Possible are actions or change of the state of
  the object

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State

• State is described by rectangle with round
  corners, divided in three parts (similar to class
  description)
• Activities consist of actions and events entry
  (describe what happens when object enter in the
  state), exit (describe what happens when object
  exit the state), do (describe what happens when
  object is in some state)

name
state variable
activity
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Example fax in idle and sending state
faxing
idle
Date Current date Time Fax start time Phone
NumberOwner Owner Name
Date Current date Time Fax start time Phone
NumberOwner Owner Name
entry/key in remote number exit/complete
transmission do/add datestamp do/add
timestamp do/add phone number do/ add owner do/
pull pages through do/paginate
entry/fax complete exit/begin faxing do/show
date do/show time
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Details for transition events and actions

• Description of the events that triggers the
  transition (trigger event) and action that by
  execution enable transition from one to other
  state are added on the line of transition
  (divided by /).
• Transition from one to other state is possible
  without associated action or event (trigger less
  transition).
• example

trigger event
Shut down
Turn PC
Initializing
Working
Shutting down
do/Bootup
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Guard conditions
Shut down
Initializing
Turn PC
Shutting down
Working
do/Bootup
Key stroke or mouse movement
Is time out
Screen saving

• guard condition
• (Boolean expression)

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Event

• Happens in time and space, but without time
  spending
• Everything that has consequences is modeled as an
  Event
• Specific event occurrence is instance of the
  event (event instance) Similarly like class -
  object
• Event could have parameters, that characterize
  instance of event (as attributes that distinct
  objects from class)
• Can form hierarchical structure
• Events are of implicit and explicit types signal
  events calling events transition events time
  events.

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Signal event

• Is named entity that is explicitly intended as a
  communication tool between two objects. The
  reception of a signal is an event of receiving
  object.
• Signal is asynchronous one way communication
• To model two way communication multiple signals
  are used (at least one in each direction)
• Could be defined as classifier with stereotype
  ltltsignalgtgt in class diagrams and parameters
  defined as attributes
• As classifiers could be defined also as
  generalization

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Example Signal event defined as generalization
(similarly as classes)
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Call event

• Is reception of a call by an object that chooses
  to implement an operation as a state machine
  rather than as a fixed procedure..
• The receiver chooses whether an operation will be
  implemented as a method or a call event trigger
  in a state machine.
• The parameters of the operation are parameters of
  the event.
• Once the receiving object process the call event
  (with taking or failing transition) controls
  return to the calling object.
• Unlike ordinary calls, the receiver of a call
  event may continue its own execution in parallel
  with the caller.

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Change event

• Is satisfaction of the Boolean expression that
  depends on values of certain parameters.
• This is declarative way to wait until a condition
  is satisfied.
• It must be used by care, because it represent a
  continuous and potentially non local computation.
  
• Difference comparing with guard condition is that
  guard event is evaluated once when the trigger
  event on the transition occurs and the receiver
  handles the event. If it is false transition do
  not ocure. Change event is evaluated continuously
  until it become true at wich time transition
  ocure.

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Time event

• Represent the passage of time
• Could be specified as absolute time (time in day)
  or relative time (time elapsed since given event)

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Example
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State

• Describe a period of time during the life of an
  object of a class. It can be characterized with
  three complementary ways
• Set of object values qualitatively similar
• As a period of time during which an object waits
  for some event(s) to occur
• As a period of time during which an object
  perform some ongoing activity
• State may have name or can be anonymous. In state
  diagrams states are connected by transitions.
  Transitions are processed by states they leave.

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Transition

• Transition that leaves one state define response
  of an object in the state to the occurrence of an
  event
• In general, a transition has an event trigger, a
  guard condition, an action and a target state.
• External transition changes the active state. Is
  described with text attached to the transition
  arrow.

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Types of transition
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Notation in the state diagrams
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Trigger events

• Trigger is an event that enable transition. It
  may have parameters, available to an action on
  the transition.
• If signal has descendants any its descendant
  enables the transition.
• Example if transition has MouseButtom as trigger
  MouseButtomDown will also trigger transition
• An object handles events one in time. A
  transition must be fired at the time object
  handle event the events are not remembered until
  later (except special case of deferred events).
  Events that do not trigger transition are lost
  or ignored

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Guard condition

• Transition may have guard condition, which is
  Boolean expression. It may reference attributes
  of the object that owns the state machine, as
  well as parameters of the trigger event
• It is evaluated when a trigger event occur. If
  condition is true then transition fires, if
  it is false it will not fire.
• If condition later become true it is late to
  fire transition.
• If two conflict transitions are enabled at the
  same time, one of them fires non
  deterministically.
• A transition on a nested states takes precedence
  over transition on one of its enclosing states.

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Completion transition

• Transition that lacks an explicit trigger event
  is triggered y the completion of activity in the
  state that it leaves.
• Action
• Is executed when transition fires and normally is
  short calculation, assignment statement or
  sequence of short statements, sending signal to
  other object, calling an operation, setting
  return values, creating or destroying objects,
  executed before next event.
• In practice entering events are placed in queue
  if action is not executed until next event.

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Kind of actions
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• Change of state
• After the execution of the action the target
  state of transition become active. This may
  trigger exit or entry actions
• Nested states
• Are states nested in a given state. A transition
  leaving an outer state is applicable to all
  states nested in it. Transition is eligible to
  fire whenever any nested state is active.

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Example
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Composite states

• Composite state consist of sequential subsets of
  states or concurrent sub states.
• Decomposition into disjoint sub states is a kind
  of specialization of the state.
• An outer state is refined into several inner
  states, each of which inherits the transitions of
  the outer state.
• Only one sequential sub state can be active at
  one time. The outer state represent the condition
  of being in any one of the inner states.

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Example
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Composite state with concurrent sub states
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History states

• If it is not stated which of the sub states is
  activated in a composite state, a starting sub
  state will be activated
• If model of an object is design where we wont to
  remember a sub state from which transition was
  made outside the composite state and we want to
  return to the same sub state after activation of
  the composite state, we will use history state

H
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Example
After the first entrance in history state there
is no history and beginning is collecting
state If composite state was left in Copying
state when we return to the sub state BackingUp
continuation will be with Copying state
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Example Complex states and transitions
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Reusable components
Usage of the state fragments in other state
diagrams with defined name of sub machine
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Activity diagram

• Model of dynamical behavior of the system
• Activity diagram is special form of the state
  machine. It represent flow chart that describes
  change of the control from one to other activity
  (sequential and parallel steps in an process
• Activity diagram contains states of activities
  (being clauses - commands in procedures).
  Transition is automatic after command is executed
  
• Usage imply no interruptions by external events.
  In a case of interruptions better is to use SD

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• Activity is non atomic execution in the framework
  of state machine. Result is some action
  containing atomic actions that change state or
  return values
• Actions (similar to activities) but are atomic
  and do not allow transition during their activity
• Diagrams can contain also objects
• AD are important for construction of the
  executable parts of the system in software
  engineering and re-engineering.
• They are used for modeling flow of one object
  during its change of states in various moments
  of control

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Activity state
Simple transition
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Trrigerless transition
guard condition
fork
Flow of values of an object
join
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Activity state and actions
Text or concrete programming language
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Organization of the activities according
responsibilities