Karolina Muszyńska
Based on: S. Wrycza, B. Marcinkowski, K. Wyrzykowski „Język UML 2.0 w modelowaniu SI”
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Dynamic view – statechart diagrams
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role
basic concepts
advanced concepts
examples
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Statechart diagram, also called state machine, is
one of the five UML diagrams used to model
dynamic nature of a system. It defines different
states of an object during its lifetime and these
states are changed by events.
Statechart diagram describes the flow of control
from one state to another state. States are
defined as a condition in which an object exists
and it changes when some event is triggered
Statechart diagrams are useful to model reactive
systems. Reactive system can be defined as a
system that responds to external or internal
events.
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State - is a circumstance in which an object is
situated in its life cycle, when it meets a certain
condition, performs an operation or waits for an
event to occur.
Transition is a relationship between two states,
indicating that the object being in the first state
will perform certain actions and move to the
other state, whenever a specific event occurs and
certain conditions are met.
Initial state is the initiation of the statechart
diagram
Final state is the termination of the statechart
diagram
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Initial state
Transition
State
Final state
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Sections of graphical symbol of state:
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name section – place for the state name
internal operations section - lists the internal
operations performed when an object achieves a
certain state. Type of the internal operation is
identified by one of the keywords:
◦ entry - an operation automatically performed on the object the
moment it achieves the state (there may be only one within a
state),
◦ exit - operation performed when an object leaves the state
(there may be only one within a state),
◦ do - operation performed continuously on the object being in a
given state (there can be many such operation within a state)
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Sections of graphical symbol of state:
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internal transitions section - indicates specific
cases of transitions, execution of which does not
lead to a change of state. Internal transitions do
not have their own graphical symbol but are
specified in the state area
decomposition section – informs about
decomposition of the state into sub-states
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Name section
Internal
operations
section
Decomposition
section
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Classification of states:
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Simple state - a state that does not contain any
sub-states or orthogonal regions
Composite state - a state, which contains either
sub-states or is divided into orthogonal regions
Sub-state – a state machine into which a
composite state is decomposed (a sub-state can
be either direct or indirect depending on the level
of decomposition)
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Substate of the decomposed
composite state ‘Received’
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Orthogonal region – concept used for showing
states and transitions within in a composite
state, which are activated concurrently.
Transitions can cross composite states
boundaries. All orthogonal regions must be
realized in order for the state to be completed.
Pseudo-state is an abstract category of
statechart diagram modeling, which allows for
organizing complex transitions by the use of fork
node, join node, junction, decision node,
termination, etc.
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Pseudo-state
(junction point)
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Orthogonal region
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Transition types:
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simple - occurring between the source and target state,
return - where the source and target states are the same
state,
internal – constituting one of the elements of a state,
local - indicating transitions between any sub-states of a
composite state,
external - leaving a composite state and directed to
another state or pseudo-state,
high level or group - leaving composite states and
indicating the necessity of leaving all sub-states of this
composite state before transition,
complex – chain of transitions joined or forked, linked by a
junction or decision node,
automatic – without any associated event or condition.
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Types of state machines:
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Protocol state machines- concentrate on a
specific object and present available and
permitted transitions between the states of this
object
Behavioral state machines- present transitions
between states of many objects in a wider
context of system, subsystem or use case
behavior
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Events - stimuli sent by objects, which initiate
transitions from one state to another
There are five types of events:
◦ signal – asynchronous stimulus transmitted between two
objects (e.g. signal from a sensor),
◦ call event – calling operations of one object by another
object (e.g. login, register),
◦ time event – event, which occurs after a certain period of
time (e.g. after (3 hrs.)),
◦ status change event – event, which occurs at a certain
point of time (e.g. when (date = 1 July)
◦ deferred event – event, which is not supported within a
given state but added to the deferred events queue (e.g.
summary of Receivables /defer)
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Determination of the type of created state
machine and identification of objects
Identification of possible states of a state
machine
Determination of the hierarchy of states, substates and orthogonal regions
Linking the states and their sub-states with
transitions
Application of adequate pseudo-states
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