![A transition is drawn as an arrow between states annotated with a
transition string
• The transition string denotes the event and consequent action
• Only one form of arrowhead is used on statecharts
• The distinction between call events and signal events must be deducted
from elsewhere e.g. an interaction diagram
A transition string is described as
• Event-signature [guard-condition]/action-expression^object.message
• If the guard condition is met the transition occurs immediately
Transitions](https://image.slidesharecdn.com/5-statediagramsppt-171003201352/85/State-Diagrams-12-320.jpg)
![State Diagram Example
Checking
do / check
Item
Dispatching
do / initiate
delivery
Ordering Delivering
*[all items checked]
get next item
[all items checked
&& some items not
in stock]
Order Item
[all items checked &&
all items available]
Dispatch items
[all items available]
Item
received
delivery
get first item
Canceling
cancelled
Exit/ Item received
do / order Item
entry / deliver
Items
do / Remove
Item
some items
not in stock
all items
in stock](https://image.slidesharecdn.com/5-statediagramsppt-171003201352/85/State-Diagrams-16-320.jpg)
State Diagrams
- 1. SARDAR PATELSARDAR PATEL COLLEGE OF ENGINEERING,COLLEGE OF ENGINEERING, BAKROLBAKROL INFORMATION TECHNOLOGYINFORMATION TECHNOLOGY DEPARTMENTDEPARTMENT
- 2. TOPIC NAME : State Diagram SUBJECT NAME : OBJECT ORIENTED PROGRAMMING Using Java(2140705) STUDENT’S NAME ENROLLMENT NUMBER Suken Vaghela 151240116061 Sunil Jethvani 151240116062 Vaidik Trivedi 151240116064 INFORMATION TECHNOLOGY FACULTY NAME: PROF. RONAK PATEL
- 4. What is State Diagram? • Specifically a state diagram describes the behavior of a single object in response to a series of events in a system. Sometimes it's also known as a Harel state chart or a state machine diagram. This UML diagram models the dynamic flow of control from state to state of a particular object within a system.
- 5. State Diagrams • State diagrams describe the life of an object using three main elements: • States of an object • Transitions between states • Events that trigger the transitions • A state diagram or statechart specifies a state machine • A state machine is described for a class • Each object has it’s own state machine
- 6. States • Show what the dependencies are between the state of an object and its reactions to messages or other events • State • is a condition or situation during the life of an object within which it performs some activity, or waits for some events • Has a name • Has actions -- execute the state • Has internal transitions -- transitions cause no change in a state • substates -- the nested structure of a state involving disjoint or concurrent substates
- 7. States • For example: entry/unlock door do/prepare materials telephone rings/answer telephone include/lecture state exit/lock door At Work state name action performed on entry to state activity performed while in state action performed on arrival of named event name of a sub-state machine action performed on leaving state
- 8. Actions and Activities • Action • is an executable atomic computation • includes operation calls, the creation or destruction of another object, or the sending of a signal to an object • associated with transitions and during which an action is not interruptible -- e.g., entry, exit • Activity is associated with states • Non-atomic or ongoing computation • May run to completion or continue indefinitely • Will be terminated by an event that causes a transition from the state in which the activity is defined
- 9. Events • An event signature is described as Event-name (comma-separated-parameter-list) • Events appear in the internal transition compartment of a state or on a transition between states • An event may be one of four types • Signal event • Corresponding to the arrival of an asynchronous message or signal • Call event • Corresponding to the arrival of a procedural call to an operation • Time event • Change event
- 10. Time Event • A time event occurs after a specified time has elapsed • Event name is specified as keyword after • Parameter list is an expression evaluating to a time interval • after(10 seconds after state “At Work” is entered) • No specified start time implies “since entry to the current state” • after(2 seconds)
- 11. Change Event • A change event occurs whenever a specified condition is met • Event name is specified as keyword when • Parameter list is a boolean expression • The event occurs when both of the following conditions are met, irrespective of the order when they happen • The expression evaluates to true • The object is in the required state • For example • when (state = At Work) • when (date = January 1 2007)
- 12. A transition is drawn as an arrow between states annotated with a transition string • The transition string denotes the event and consequent action • Only one form of arrowhead is used on statecharts • The distinction between call events and signal events must be deducted from elsewhere e.g. an interaction diagram A transition string is described as • Event-signature [guard-condition]/action-expression^object.message • If the guard condition is met the transition occurs immediately Transitions
- 13. Transitions • A transition whose string contains neither an event signature nor a guard condition is said to be unlabeled • Occurs immediately • May still carry an action expression
- 14. Transitions • A transition is triggered when its event occurs • If the guard condition is met, the transition is fired • If the condition is not met the event is discarded • The guard condition is checked only once • If there is no guard condition, triggering will always cause firing • Note the distinction between a guard condition and a change event • A guard condition is evaluated once, when the associated event occurs • A change event occurs whenever its associated condition is met • Behaviour is as if the condition were being continually evaluated
- 15. State Diagrams notation PaidUnpaid paying Invoice created Invoice destroyed name state final stateInitial state transition event
- 16. State Diagram Example Checking do / check Item Dispatching do / initiate delivery Ordering Delivering *[all items checked] get next item [all items checked && some items not in stock] Order Item [all items checked && all items available] Dispatch items [all items available] Item received delivery get first item Canceling cancelled Exit/ Item received do / order Item entry / deliver Items do / Remove Item some items not in stock all items in stock
- 17. Summary In this chapter we have: • Introduced the terms used with respect to state diagrams • Discussed the context in which state diagrams are used