1. Chapter 10 Object States and The Statechart Diagram

2. Chapter 10: Object States and the Statechart Diagram
Lifetimes and Lifecycles.
Events and States.
Transitions and Actions.
The Statechart Diagram.
Object Lifecycles on the Statechart Diagram.
The State Transition Table (STT).

3. Chapter 10: Object States and the Statechart Diagram
Lifetimes and Lifecycles.
Events and States.
Transitions and Actions.
The Statechart Diagram.
Object Lifecycles on the Statechart Diagram.
The State Transition Table (STT).

4. In the real world (See Chapter 5):
Chapter 10: Object States and the Statechart Diagram Lifetimes and Lifecycles.
In the real world (See Chapter 5):
A Purchase Order
begins life as a request document,
gets authorized at various levels,
goes out to a vendor,
is fulfilled by receiving the goods,
and finally is archived for future reference.

5. States in the real world:
Chapter 10: Object States and the Statechart Diagram Lifetimes and Lifecycles.
States in the real world:
Many objects in the real world go through a predictable cycle
From their creation,
Through their useful life,
From stage to stage
Until they die or are somehow disposed of
(Archived or deleted or whatever.)

6. Object Behaviors State Changes Business Events cause which cause
Chapter 10: Object States and the Statechart Diagram Lifetimes and Lifecycles.
Business Events
cause
State Changes
which cause
Object Behaviors
to be executed.

7. As the act or experience of changing from one state to another.
Chapter 10: Object States and the Statechart Diagram Lifetimes and Lifecycles.
We define a
State Transition
As the act or experience
of changing from one state to another.

8. Lifecycle. As we follow an object from state to state,
Chapter 10: Object States and the Statechart Diagram Lifetimes and Lifecycles.
As we follow an object from state to state,
it traces what we can call its
Lifecycle.

9. is to discover Operations for the classes we found in the
Chapter 10: Object States and the Statechart Diagram Lifetimes and Lifecycles.
So our goal in studying
Object Lifecycles
is to discover Operations
(i.e., Behaviors)
for the classes we found in the
earlier steps.

10. Here’s an example using a
Chapter 10: Object States and the Statechart Diagram Lifetimes and Lifecycles.
Here’s an example using a
library book . . .

11. Our typical library book Begins its day on the shelf. . .
Chapter 10: Object States and the Statechart Diagram Lifetimes and Lifecycles.
Our typical library book
Begins its day on the shelf. . .
1. Shelved
1. Shelved

12. And when a Subscriber comes along This is a Business Event . . .
Chapter 10: Object States and the Statechart Diagram Lifetimes and Lifecycles.
1. Shelved
1. Shelved
And when a Subscriber comes along
and borrows the Book
This is a Business Event . . .

13. “Signed Out.” The state of the Book changes to
Chapter 10: Object States and the Statechart Diagram Lifetimes and Lifecycles.
The state of the Book changes to
“Signed Out.”
1. Shelved
1. Shelved
2. Signed Out

14. When the Subscriber brings it back. . .
Chapter 10: Object States and the Statechart Diagram Lifetimes and Lifecycles.
When the Subscriber brings it back. . .
The state of the Book changes to
“Checked In.”
1. Shelved
1. Shelved
3. Checked In
2. Signed Out

15. And when the Librarian puts it back on the shelf,
Chapter 10: Object States and the Statechart Diagram Lifetimes and Lifecycles.
And when the Librarian puts it back on the shelf,
The state of the Book changes back to“Shelved.”
1. Shelved
1. Shelved
3. Checked In
2. Signed Out

16. does not repeat, A loop like this is an Operational Lifecycle,
Chapter 10: Object States and the Statechart Diagram Lifetimes and Lifecycles.
A loop like this is an
Operational Lifecycle,
concerned with the regular operation of the users’ business.
Many objects have a life that
does not repeat,
But goes stage to stage
from “birth” to “death”
(i.e., delete, archive, or whatever.)
That kind is called a Lifetime

17. State. Definition: State: At any moment, an object exists
Chapter 10: Object States and the Statechart Diagram Lifetimes and Lifecycles.
Definition:
State: At any moment, an object exists
in a certain condition or manner of being,
and this we say is its
State.

18. Chapter 10: Object States and the Statechart Diagram
Lifetimes and Lifecycles.
Transitions and Actions.
The Statechart Diagram.
Object Lifecycles on the Statechart Diagram.
The State Transition Table (STT).
Events and States.

19. A noteworthy happening.
Chapter 10: Object States and the Statechart Diagram Events and States.
Event:
A noteworthy happening.
(Webster)
We say that:
An Event is received by an object,
Which really means the event
happens to that object.

20. And once the event has happened to it, The object is in a new state.
Chapter 10: Object States and the Statechart Diagram Events and States.
And once the event has happened to it,
The object is in a new state.

21. we must change the value of at least
Chapter 10: Object States and the Statechart Diagram Events and States.
Generally,
To record a business event,
we must change the value of at least
one attribute.
Since the attribute values can be said to represent the object’s state,
this causes a
State Transition.

22. “Status” attribute, and
Chapter 10: Object States and the Statechart Diagram Events and States.
In fact, many classes have a
“Status” attribute, and
the domain of its permissible values
Gives the set of possible states
for that class.

23. Chapter 10: Object States and the Statechart Diagram
Lifetimes and Lifecycles.
Events and States.
The Statechart Diagram.
Object Lifecycles on the Statechart Diagram.
The State Transition Table (STT).
Transitions and Actions.

24. of changing from one state to another.
Chapter 10: Object States and the Statechart Diagram Transitions and Actions.
Definition:
State Transition:
The act or experience
of changing from one state to another.

25. Chapter 10: Object States and the Statechart Diagram 10. 3
Chapter 10: Object States and the Statechart Diagram Transitions and Actions.
We define an
Object Lifecycle
As consisting of the various states that an object may transition through,
The set of permissible transitions,
And the sequencing of those states and transitions,
as it progresses from its initial creation to its eventual disposal.

26. Action: An Action is a behavior associated with a state or transition,
Chapter 10: Object States and the Statechart Diagram Transitions and Actions.
Action:
An Action is a behavior associated with a state or transition,
Executed each time the object enters or leaves that state (or executes that transition)

27. “Signed Out.” When the state of the Book changes to
Chapter 10: Object States and the Statechart Diagram Lifetimes and Lifecycles.
When the state of the Book changes to
“Signed Out.”
1. Shelved
1. Shelved
There are some things
that must happen,
to keep track of
all the loans
2. Signed Out

28. entry / Loan.L1: Request Link to Subscriber
Chapter 10: Object States and the Statechart Diagram Lifetimes and Lifecycles.
When the state of the Book changes to
“Signed Out.”
1. Shelved
1. Shelved
When it is loaned out, the Book must in some way be attached to the borrower
2. Signed Out
entry / Loan.L1: Request Link to Subscriber
exit / UpdateTimeIn()
2. Signed Out
entry / Loan.L1: Request Link to Subscriber

29. entry / Loan.L1: Request Link to Subscriber
Chapter 10: Object States and the Statechart Diagram Lifetimes and Lifecycles.
When the state of the Book changes to
“Signed Out.”
1. Shelved
And when it leaves the state of “Signed Out,” it must update the Date and Time In.
1. Shelved
2. Signed Out
entry / Loan.L1: Request Link to Subscriber
exit / UpdateTimeIn()
2. Signed Out
exit / UpdateTimeIn()

30. Action: stays within this state.
Chapter 10: Object States and the Statechart Diagram Transitions and Actions.
Action:
Each Action is attached to either the entry into the state, or the exit from the state.
Sometimes an Action is attached to a transition
and executes during the transition.
Sometimes an Action is attached to an event,
and executes while the object
stays within this state.
We’ll look at these ones later . . .

31. within the box for the class
Chapter 10: Object States and the Statechart Diagram Transitions and Actions.
On the Statechart Diagram, Actions may be spelled out
within the box for the class
(Or documented separately if too many)
At Analysis time, we just want to find Names for the actions,
to be expanded and spelled out in the Design phase.

32. Actions can do anything:
Chapter 10: Object States and the Statechart Diagram Transitions and Actions.
Actions can do anything:
Update attributes,
Create instances,
Send messages to other classes,
i.e., generate an event
to be received by another class
and cause a transition in that other class
(or even create an instance there.)

33. Object Behaviors State Changes Remember: Business Events cause
Chapter 10: Object States and the Statechart Diagram Lifetimes and Lifecycles.
Remember: Business Events
cause
State Changes
which cause
Object Behaviors
(i.e., Actions)
to be executed.

34. Object Behaviors The goal of the Statechart Diagram
Chapter 10: Object States and the Statechart Diagram Transitions and Actions.
The goal of the Statechart Diagram
Is to find the Actions
So from them we may identify
And later spec out in detail, the
Object Behaviors
and Methods.

35. And the tool for studying and documenting object lifecycles is the
Chapter 10: Object States and the Statechart Diagram Transitions and Actions.
And the tool for studying and
documenting object lifecycles is the
Statechart Diagram . . .

36. Chapter 10: Object States and the Statechart Diagram
Lifetimes and Lifecycles.
Events and States.
Transitions and Actions.
Object Lifecycles on the Statechart Diagram.
The State Transition Table (STT).
The Statechart Diagram.

37. Chapter 10: Object States and the Statechart Diagram 10. 4
Chapter 10: Object States and the Statechart Diagram The Statechart Diagram For a Library Book.
1. Shelved
entry / Update Date & time Shelved
Event B4: «create»
Book is Purchased
Event B1: Subscriber
Requests Loan
/ Update Date & Time Out
Event B3: Librarian
Shelves Book
3. Checked In
entry / Loan.L2: Archive Loan
2. Signed Out
entry / Loan.L1: Request Link to Subscriber
exit / UpdateDateAndTimeIn()
Event B2: Subscriber
Returns Book

38. a large black dot Events are shown with arrows.
Chapter 10: Object States and the Statechart Diagram The Statechart Diagram Notation
Events are shown with arrows.
The event that causes the instance to be created
is shown as coming from
a large black dot
and is “stereotyped” «create»
(e.g., Event B4)
Event B2: Subscriber
Returns Book
1. Shelved
2. Signed Out
3. Checked In
Update Date/time Shelved
Event B1: Subscriber
Requests Loan
Update Date/time Out
Generate Event SO1:
Request Link to Subscriber
Update Date/Time In
Generate Event SO2:
Archive Sign-Out
Event B3: Librarian
Shelves Book
Event B4:
Book is Purchased
Event B1: Subscriber
Requests Loan
/ Update Date/Time Out
Event B2: Subscriber
Returns Book
Event B3: Librarian
Shelves Book
Event B4: «create»
Book is Purchased
2. Signed Out
entry / Loan.L1: Request Link to Subscriber
exit / UpdateDateAndTimeIn()
1. Shelved
entry / Update Date & time Shelved
3. Checked In
entry / Loan.L2: Archive Loan

39. State numbers are unique within that Statechart Diagram
Chapter 10: Object States and the Statechart Diagram The Statechart Diagram Notation
State numbers are unique within that Statechart Diagram
e.g., “2: Signed Out”
Event numbers are unique within the project
Event numbers have a prefix telling what class they belong with, e.g.:
“B3: Librarian Shelves Book” belongs in the Book class.
“L1: Create Loan Instance” is in the Loan class.
Event B1: Subscriber
Requests Loan
/ Update Date/Time Out
Event B2: Subscriber
Returns Book
Event B3: Librarian
Shelves Book
Event B4: «create»
Book is Purchased
2. Signed Out
entry / Loan.L1: Request Link to Subscriber
exit / UpdateDateAndTimeIn()
1. Shelved
entry / Update Date & time Shelved
3. Checked In
entry / Loan.L2: Archive Loan

40. Now let’s follow the Book through its daily routine. . .
Chapter 10: Object States and the Statechart Diagram The Statechart Diagram Notation
Now let’s follow the
Book through
its daily routine. . .
Event B1: Subscriber
Requests Loan
/ Update Date/Time Out
Event B2: Subscriber
Returns Book
Event B3: Librarian
Shelves Book
Event B4: «create»
Book is Purchased
2. Signed Out
entry / Loan.L1: Request Link to Subscriber
exit / UpdateDateAndTimeIn()
1. Shelved
entry / Update Date & time Shelved
3. Checked In
entry / Loan.L2: Archive Loan

41. Update Date & Time Shelved
Chapter 10: Object States and the Statechart Diagram The Statechart Diagram
The Book is purchased (Event B4) and enters
its initial state (State 1: Shelved)
As it enters State 1, it executes the Entry Action for that state,
Update Date & Time Shelved 
Event B1: Subscriber
Requests Loan
/ Update Date/Time Out
Event B2: Subscriber
Returns Book
Event B3: Librarian
Shelves Book
Event B4: «create»
Book is Purchased
2. Signed Out
entry / Loan.L1: Request Link to Subscriber
exit / UpdateDateAndTimeIn()
1. Shelved
entry / Update Date & time Shelved
3. Checked In
entry / Loan.L2: Archive Loan

42. (Event B1) A subscriber (customer) borrows the Book
Chapter 10: Object States and the Statechart Diagram The Statechart Diagram
A subscriber (customer) borrows the Book
(Event B1)
This causes it to transition to State 2: Signed Out
As the Book is in transition it executes the Action for that transition:
Update Date & Time Out
Then, as it enters State 2, it
executes the Entry Action
for that state,
Request Link to Subscriber
Event B1: Subscriber
Requests Loan
/ Update Date/Time Out
Event B2: Subscriber
Returns Book
Event B3: Librarian
Shelves Book
Event B4: «create»
Book is Purchased
2. Signed Out
entry / Loan.L1: Request Link to Subscriber
exit / UpdateDateAndTimeIn()
1. Shelved
entry / Update Date & time Shelved
3. Checked In
entry / Loan.L2: Archive Loan

43. Action: An Action is a behavior Associated with a state or transition,
Chapter 10: Object States and the Statechart Diagram The Statechart Diagram.
Action:
An Action is a behavior
Associated with a state or transition,
Executed each time
The object enters or leaves that state
or executes that
transition.
Event B1: Subscriber
Requests Loan
/ Update Date/Time Out
Event B2: Subscriber
Returns Book
Event B3: Librarian
Shelves Book
Event B4: «create»
Book is Purchased
2. Signed Out
entry / Loan.L1: Request Link to Subscriber
exit / UpdateDateAndTimeIn()
1. Shelved
entry / Update Date & time Shelved
3. Checked In
entry / Loan.L2: Archive Loan

44. In other words, An Action is a set of things that the object must do
Chapter 10: Object States and the Statechart Diagram The Statechart Diagram
In other words,
An Action is
a set of things that the object must do
when it transitions into or out of a state
or during a transition.
Event B1: Subscriber
Requests Loan
/ Update Date/Time Out
Event B2: Subscriber
Returns Book
Event B3: Librarian
Shelves Book
Event B4: «create»
Book is Purchased
2. Signed Out
entry / Loan.L1: Request Link to Subscriber
exit / UpdateDateAndTimeIn()
1. Shelved
entry / Update Date & time Shelved
3. Checked In
entry / Loan.L2: Archive Loan

45.  Request Link to Subscriber Note that in this case, the Book object
Chapter 10: Object States and the Statechart Diagram The Statechart Diagram
Note that in this case, the Book object
updates the Date and Time Out 
Request Link to Subscriber
as it transitions
from State 1 to State 2,
And as it enters State 2, generates an
Event L1:
Event B1: Subscriber
Requests Loan
/ Update Date/Time Out
Event B2: Subscriber
Returns Book
Event B3: Librarian
Shelves Book
Event B4: «create»
Book is Purchased
2. Signed Out
entry / Loan.L1: Request Link to Subscriber
exit / UpdateDateAndTimeIn()
1. Shelved
entry / Update Date & time Shelved
3. Checked In
entry / Loan.L2: Archive Loan

46. The Event SO1 is then received by the Statechart
Chapter 10: Object States and the Statechart Diagram The Statechart Diagram
The Event SO1 is then received by the Statechart
Diagram for the Loan class.
This causes a Loan instance to be created
in its initial state, State 1: Current.
1. Current
Event L1: Request Link to Subscriber
«create»
Update Date/time Out
Generate Event SO1:
Request Link to subscriber
Event B1: Subscriber
Requests Loan
/ Update Date/Time Out
Event B2: Subscriber
Returns Book
Event B3: Librarian
Shelves Book
Event B4: «create»
Book is Purchased
2. Signed Out
entry / Loan.L1: Request Link to Subscriber
exit / UpdateDateAndTimeIn()
1. Shelved
entry / Update Date & time Shelved
3. Checked In
entry / Loan.L2: Archive Loan

47.  Next, Event B2 happens, The Subscriber returns the Book
Chapter 10: Object States and the Statechart Diagram The Statechart Diagram
Next, Event B2 happens,
The Subscriber returns the Book
And the Book transitions to State 3.
Event B1: Subscriber
Requests Loan
/ Update Date/Time Out
Event B2: Subscriber
Returns Book
Event B3: Librarian
Shelves Book
Event B4: «create»
Book is Purchased
2. Signed Out
entry / Loan.L1: Request Link to Subscriber
exit / UpdateDateAndTimeIn()
1. Shelved
entry / Update Date & time Shelved
3. Checked In
entry / Loan.L2: Archive Loan 
3. Checked In
entry / Loan.L2: Archive Loan

48. it executes the Exit Action, UpdateDateAndTimeIn()
Chapter 10: Object States and the Statechart Diagram The Statechart Diagram
As the Book leaves State 2: Signed out
it executes the Exit Action,
UpdateDateAndTimeIn()
Event B1: Subscriber
Requests Loan
/ Update Date/Time Out
Event B2: Subscriber
Returns Book
Event B3: Librarian
Shelves Book
Event B4: «create»
Book is Purchased
2. Signed Out
entry / Loan.L1: Request Link to Subscriber
exit / UpdateDateAndTimeIn()
1. Shelved
entry / Update Date & time Shelved
3. Checked In
entry / Loan.L2: Archive Loan
exit / UpdateDateAndTimeIn() 

49. Generate Event L2: Archive Loan
Chapter 10: Object States and the Statechart Diagram The Statechart Diagram
As the Book enters State 3: Checked In
It executes the Entry Action,
Generate Event L2: Archive Loan.
Event B1: Subscriber
Requests Loan
/ Update Date/Time Out
Event B2: Subscriber
Returns Book
Event B3: Librarian
Shelves Book
Event B4: «create»
Book is Purchased
2. Signed Out
entry / Loan.L1: Request Link to Subscriber
exit / UpdateDateAndTimeIn()
1. Shelved
entry / Update Date & time Shelved
3. Checked In
entry / Loan.L2: Archive Loan
Generate Event L2:
Archive Loan

50. The Loan instance Transitions to State 2: Archived, and
Chapter 10: Object States and the Statechart Diagram The Statechart Diagram
When Event L2 is received by the Statechart Diagram for the Loan class,
The Loan instance Transitions to State 2: Archived, and
executes the Action for that transition:
UpdateAverageDurationOfLoansAllBooks()
Event L1: Request Link to Subscriber
«create»
Event L2: Loan is Archived
/ UpdateAverageDurationOfLoan sAllBooks()
1. Current
Event B1: Subscriber
Requests Loan
/ Update Date/Time Out
Event B2: Subscriber
Returns Book
Event B3: Librarian
Shelves Book
Event B4: «create»
Book is Purchased
2. Signed Out
entry / Loan.L1: Request Link to Subscriber
exit / UpdateDateAndTimeIn()
1. Shelved
entry / Update Date & time Shelved
3. Checked In
entry / Loan.L2: Archive Loan
2. Archived
entry / Update Archive Status

51. Chapter 10: Object States and the Statechart Diagram 10. 4
Chapter 10: Object States and the Statechart Diagram The Statechart Diagram
Then, as the Loan object enters State 2: Archived,
It executes the Entry Action
Update Archive Status
entry / Update Archive Status
Event L1: Request Link to Subscriber
«create»
1. Current
Event L2: Loan is Archived
/ UpdateAverageDurationOfLoansAllBooks()
Event B1: Subscriber
Requests Loan
/ Update Date/Time Out
Event B2: Subscriber
Returns Book
Event B3: Librarian
Shelves Book
Event B4: «create»
Book is Purchased
2. Signed Out
entry / Loan.L1: Request Link to Subscriber
exit / UpdateDateAndTimeIn()
1. Shelved
entry / Update Date & time Shelved
3. Checked In
entry / Loan.L2: Archive Loan
2. Archived

52. The last two events in the cycle are unrelated:
Chapter 10: Object States and the Statechart Diagram The Statechart Diagram
The last two events in the cycle are unrelated:
Event B3 puts the Book back in State 1: Shelved.
Event B1: Subscriber
Requests Loan
/ Update Date/Time Out
Event B2: Subscriber
Returns Book
Event B3: Librarian
Shelves Book
Event B4: «create»
Book is Purchased
2. Signed Out
entry / Loan.L1: Request Link to Subscriber
exit / UpdateDateAndTimeIn()
1. Shelved
entry / Update Date & time Shelved
3. Checked In
entry / Loan.L2: Archive Loan

53. and deletes all the archived Sign-Outs, after a suitable period.
Chapter 10: Object States and the Statechart Diagram The Statechart Diagram
Finally, Timer Event L3 happens 
After(90 Days)
and deletes all the archived Sign-Outs, after a suitable period.
Event L1: Request Link to Subscriber
«create»
1. Current
Event L2: Loan is Archived
/ UpdateAverageDurationOfLoansAllBooks()
Event B1: Subscriber
Requests Loan
/ Update Date/Time Out
Event B2: Subscriber
Returns Book
Event B3: Librarian
Shelves Book
Event B4: «create»
Book is Purchased
2. Signed Out
entry / Loan.L1: Request Link to Subscriber
exit / UpdateDateAndTimeIn()
1. Shelved
entry / Update Date & time Shelved
3. Checked In
entry / Loan.L2: Archive Loan
2. Archived
entry / Update Archive Status
Event L3: After(90 days)
/ Delete Archived Loan

54. Note that in this example,
Chapter 10: Object States and the Statechart Diagram The Statechart Diagram
Note that in this example,
The Loan has a Lifetime,
And the Book has a repeating Lifecycle . . .
Event L1: Request Link to Subscriber
«create»
1. Current
Event L2: Loan is Archived
/ UpdateAverageDurationOfLoansAllBooks()
Event B1: Subscriber
Requests Loan
/ Update Date/Time Out
Event B2: Subscriber
Returns Book
Event B3: Librarian
Shelves Book
Event B4: «create»
Book is Purchased
2. Signed Out
entry / Loan.L1: Request Link to Subscriber
exit / UpdateDateAndTimeIn()
1. Shelved
entry / Update Date & time Shelved
3. Checked In
entry / Loan.L2: Archive Loan
2. Archived
entry / Update Archive Status
Event L3: After(90 days)
/ Delete Archived Loan

55. Chapter 10: Object States and the Statechart Diagram
Lifetimes and Lifecycles.
Events and States.
Transitions and Actions.
The Statechart Diagram.
The State Transition Table (STT).
Object Lifecycles on the
Statechart Diagram.

56. An Object Lifecycle consists of the various states
Chapter 10: Object States and the Statechart Diagram Object Lifecycles on the Statechart Diagram.
Definition:
An Object Lifecycle consists of
the various states
that an object may transition through,
The set of permissible transitions,
and the sequencing
of those states and transitions.

57. Actions for each state, event and transition,
Chapter 10: Object States and the Statechart Diagram Object Lifecycles on the Statechart Diagram.
The Lifecycle also includes
Actions
for each state, event and transition,
Actions that are executed each time the object
enters or leaves that state
or executes the transition

58. “Interesting Lifecycle,”
Chapter 10: Object States and the Statechart Diagram Object Lifecycles on the Statechart Diagram
But which classes need a
Statechart Diagram?
Pick the classes we figure will have an
“Interesting Lifecycle,”
Also include those with a lifetime linked with the “interesting” ones.

59. By “Interesting” it means those with:
Chapter 10: Object States and the Statechart Diagram Object Lifecycles on the Statechart Diagram
By “Interesting” it means those with:
A repeating operational lifecycle (e.g., Library Book),
A complex lifetime with branches and backtracks (e.g., Purchase Order),
A long lifetime with many states,
Anything we judge may be a fruitful source of Actions and operations.

60. Chapter 10: Object States and the Statechart Diagram 10. 5
Chapter 10: Object States and the Statechart Diagram Object Lifecycles on the Statechart Diagram
Since all instances in a class have the same lifecycle,
It follows that they all have the same Statechart Diagram.
However, for executing its Statechart Diagram,
Each separate instance proceeds at its own pace,
As events arrive to step it through its lifecycle.
We have a name for this. . .

61. A State Machine is the set of actual historical events
Chapter 10: Object States and the Statechart Diagram Object Lifecycles on the Statechart Diagram
Definition:
A State Machine is the set of
actual historical events
that took place during the execution of a Statechart Diagram
by a particular specified
object instance.

62. that will make up the rest of the path that this instance will take
Chapter 10: Object States and the Statechart Diagram Object Lifecycles on the Statechart Diagram
Definition: State Machine
It may also include
the future events
that will make up the rest of the path
that this instance will take
through the Statechart Diagram.

63. This is different from the Statechart Diagram itself
Chapter 10: Object States and the Statechart Diagram Object Lifecycles on the Statechart Diagram
Definition: State Machine
This is different from the Statechart Diagram itself
which may be viewed as
an abstraction
of the State Machines of all the instances.

64. And now a Completeness Check
Chapter 10: Object States and the Statechart Diagram Object Lifecycles on the Statechart Diagram
And now a Completeness Check
That we must use on every Statechart Diagram. . .

65. Chapter 10: Object States and the Statechart Diagram
Lifetimes and Lifecycles.
Events and States.
Transitions and Actions.
The Statechart Diagram.
Object Lifecycles on the Statechart Diagram.
The State Transition Table (STT).

66. Let’s take another quick look at the
Chapter 10: Object States and the Statechart Diagram The State Transition Table (STT)
Let’s take another quick look at the
Library Book
Event B1: Subscriber
Requests Loan
/ Update Date/Time Out
Event B2: Subscriber
Returns Book
Event B3: Librarian
Shelves Book
Event B4: «create»
Book is Purchased
2. Signed Out
entry / Loan.L1: Request Link to Subscriber
exit / UpdateDateAndTimeIn()
1. Shelved
entry / Update Date & time Shelved
3. Checked In
entry / Loan.L2: Archive Loan

67. every possible transition has been:
Chapter 10: Object States and the Statechart Diagram The State Transition Table (STT)
We need to check that
every possible transition has been:
Assigned a destination state, or
Ruled as physically or legally impossible, or
Designated as one that should be ignored.
Event B1: Subscriber
Requests Loan
/ Update Date/Time Out
Event B2: Subscriber
Returns Book
Event B3: Librarian
Shelves Book
Event B4: «create»
Book is Purchased
2. Signed Out
entry / Loan.L1: Request Link to Subscriber
exit / UpdateDateAndTimeIn()
1. Shelved
entry / Update Date & time Shelved
3. Checked In
entry / Loan.L2: Archive Loan

68. Here is a matrix tool that will
Chapter 10: Object States and the Statechart Diagram The State Transition Table (STT)
Here is a matrix tool that will
help you do that,
It’s called a
State Transition Table . . .
Event B1: Subscriber
Requests Loan
/ Update Date/Time Out
Event B2: Subscriber
Returns Book
Event B3: Librarian
Shelves Book
Event B4: «create»
Book is Purchased
2. Signed Out
entry / Loan.L1: Request Link to Subscriber
exit / UpdateDateAndTimeIn()
1. Shelved
entry / Update Date & time Shelved
3. Checked In
entry / Loan.L2: Archive Loan

69. ? State Transition Table 1 2 3 1 Events States Ignore
Chapter 10: Object States and the Statechart Diagram The State Transition Table (STT)
State Transition Table
Events
B1: Subscriber
Requests Loan
B2: Subscriber
Returns Book
B3: Librarian
Shelves Book
is Purchased
B4: Book
States 1
0. Null
Impossible
Impossible
Impossible
1. Shelved 2
Impossible
Impossible
Impossible
2. Signed Out
Ignore 3
Impossible
Impossible ? 1
3. Checked In
Impossible
Impossible
Event B1: Subscriber
Requests Loan
/ Update Date/Time Out
Event B2: Subscriber
Returns Book
Event B3: Librarian
Shelves Book
Event B4: «create»
Book is Purchased
2. Signed Out
entry / Loan.L1: Request Link to Subscriber
exit / UpdateDateAndTimeIn()
1. Shelved
entry / Update Date & time Shelved
3. Checked In
entry / Loan.L2: Archive Loan
But what about the blank
in the bottom leftmost box?
What happens if a loan is requested
while the Book is in the Checked-In bin, waiting to go back on the shelf?

70. It would not make sense, our users tell us,
Chapter 10: Object States and the Statechart Diagram The State Transition Table (STT)
It would not make sense, our users tell us,
to refuse to lend a book when it is available from the Checked-In bin!
So our State Transition Table has highlighted a deficiency in the Statechart Diagram.
Event B1: Subscriber
Requests Loan
/ Update Date/Time Out
Event B2: Subscriber
Returns Book
Event B3: Librarian
Shelves Book
Event B4: «create»
Book is Purchased
2. Signed Out
entry / Loan.L1: Request Link to Subscriber
exit / UpdateDateAndTimeIn()
1. Shelved
entry / Update Date & time Shelved
3. Checked In
entry / Loan.L2: Archive Loan

71. So we add an arrow from State 3 to State 2
Chapter 10: Object States and the Statechart Diagram The State Transition Table (STT)
So we add an arrow from State 3 to State 2
Triggered by an Event B1: Loan Requested
Event B1: Subscriber
Requests Loan
/ Update Date/Time Out
Event B2: Subscriber
Returns Book
Event B3: Librarian
Shelves Book
Event B4: «create»
Book is Purchased
2. Signed Out
entry / Loan.L1: Request Link to Subscriber
exit / UpdateDateAndTimeIn()
1. Shelved
entry / Update Date & time Shelved
3. Checked In
entry / Loan.L2: Archive Loan
Event B1: Subscriber
Requests Loan
/ Update Date/Time Out
Event B2: Subscriber
Returns Book
Event B3: Librarian
Shelves Book
Event B4: «create»
Book is Purchased
2. Signed Out
entry / Loan.L1: Request Link to Subscriber
exit / UpdateDateAndTimeIn()
1. Shelved
entry / Update Date & time Shelved
3. Checked In
entry / Loan.L2: Archive Loan
Event B1: Subscriber
Requests Loan
/ Update Date/Time Out

72.  State Transition Table 1 2 3 2 1 And we put a ‘2’ as
Chapter 10: Object States and the Statechart Diagram The State Transition Table (STT)
State Transition Table
Events
B1: Subscriber
Requests Loan
B2: Subscriber
Returns Book
B3: Librarian
Shelves Book
is Purchased
B4: Book
States 1
0. Null
Impossible
Impossible
Impossible 
1. Shelved 2
Impossible
Impossible
Impossible
2. Signed Out
Ignore 3
Impossible
Impossible 2 1
3. Checked In
Impossible
Impossible
And we put a ‘2’ as
the destination state
in the bottom left box.
Event B1: Subscriber
Requests Loan
/ Update Date/Time Out
Event B2: Subscriber
Returns Book
Event B3: Librarian
Shelves Book
Event B4: «create»
Book is Purchased
2. Signed Out
entry / Loan.L1: Request Link to Subscriber
exit / UpdateDateAndTimeIn()
1. Shelved
entry / Update Date & time Shelved
3. Checked In
entry / Loan.L2: Archive Loan

73. End of Chapter 10