Jar chapter 4, part 1

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Chapter 4
Dynamic Modeling and Analysis
(Part I)
Object-Oriented Technology
From Diagram to Code with Visual Paradigm for UML
Curtis H.K. Tsang, Clarence S.W. Lau and Y.K.
Leung
McGraw-Hill Education (Asia), 2005

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References
 Chapter 4, Object-Oriented Technology:
From diagram to code with Visual
Paradigm for UML
 Chapters 15, 18, 21, The UML User
Guide

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What You Will Learn
 Model message flows using sequence
diagrams.
 Model message flows using the collaboration
diagrams.
 Model lifetime behaviors of an object using
state chart diagrams.
 Model performance of actions of a procedure
or an activity using activity diagrams.

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Scenario Modeling
Techniques – Interaction
Diagramme
 Scenario modeling describes how the objects
in a system interact with each other in a
scenario.
 A scenario is a sequence of events that
occurs during one particular execution path
within a use case of a system.
 Each event involves the interaction of objects
passing messages between them.

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Scenario Modeling
Techniques – Interaction
Diagramme (cont’d)
 An interaction diagram can be used to model the
collaborating objects in scenarios, showing the
 objects involved in the scenario and
 the messages sent and received by them.
 These objects may be external or internal to the system.
 The messages represent the invocation of operations of
the receiving objects.
 Two kinds of interaction diagrams: sequence diagrams
and collaboration diagrams.
 Sequence diagrams focus on the time sequencing of
messages.
 Collaboration diagrams focus on the structural
organization of the links between collaborating objects.

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Common UML Interaction
Diagram Notation
 Object Symbol
Naming Format Notation
An object of an unspecified
class.
A named object of a specified
class.
An unnamed object of a
specified class.

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Object Stereotype
Object
Category
Description Graphical Notations
Actor Object An external entity that
interacts with the
system.
Entity Object An object that models
the data in the system.
It often represents an
object in the problem
domain.

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Object Stereotype (cont’d)
Object
Category
Description Graphical Notations
Boundary
Object
An object that handles
the communication
between actor objects
and the system.
Control Object An object that models
the flow of control and
functionality that do
not naturally belong to
entity objects or
boundary objects.

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Messages
Message Description Notation
Procedure call or
other nested flow
of control
The message sender waits
for the completion of the
procedure call of the
message receiver.
Asynchronous
communication
The sender dispatches a
message and immediately
continues with the next step
of execution.

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Messages (cont’d)
Message Description Notation
Return message Message returned from the
procedure call.
Message with
travel delay
The message will take a
significant amount of time to
arrive at the receiving
object. (This is only used in
sequence diagrams.)

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Sequence Diagrams
 Interaction diagram: models the behavior of a
group of objects that work together to achieve a
user goal.
 A sequence diagram helps us identify a set of
collaborating objects involved in a scenario of a use
case.
 A sequence diagram has two dimensions: the
vertical dimension and the horizontal dimension,
respectively
 Object icons are placed horizontally at the top of the
sequence diagram, and messages are passed
between them.

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Sequence Diagrams (cont’d)

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Life Line & Activation
Object with
Lifeline
Object with
Activation

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Creation & Destruction
Object
Destruction
Object
Destruction

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Branching
Conditional
Message
Transmission

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Message that Takes Time
Message Transmission that Takes Time

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Alternate Message Reception
Alternate
Message
Reception

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Example
Life line
Creation
Deletion

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Example
Life line
Activation
iteration

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Example
Life line
collective
iteration

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Collaboration Diagrams
 Collaboration diagrams provide another way to model a
scenario.
 Shows the roles of objects and associations of objects in an
instance of collaboration.
 Focus on structures of the objects rather than temporal
sequence of operations.
 In a collaboration diagram, each object is represented by an
object icon, and links are used to indicate communication paths
on which messages are transmitted.
 Collaboration diagram = object diagram + messages between
objects.
 Messages are presented in the same way as those in a
sequence diagram; in fact, sequence diagrams and
collaboration diagrams are semantically equivalent.

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Collaboration Diagrams
(cont’d)

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Example – Telephone System

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Example – Message with Duration

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Example – An Automatic
Teller Machine (ATM)
 The ATM prompts the user to insert a card.
 The user inserts an ATM card.
 The ATM prompts the user to input the PIN.
 The user enters the PIN.
 The ATM asks the bank consortium to verify the ATM card number and
PIN.
 The bank consortium verifies the ATM card number and PIN with bank.
 The bank notifies the bank consortium that the PIN is correct.
 The bank consortium notifies the ATM the PIN is correct.
 The ATM prompts the user to select a service.
 The user selects the withdraw cash service.
 The ATM prompts the user to enter the amount to withdraw.

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Example 1 – An Automatic
Teller Machine (cont’d)
 The user enters the amount to withdraw.
 The ATM asks the bank consortium to process the request. The bank
consortium forwards the request to bank.
 The bank confirms the successful execution of the request to the bank
consortium which in turn notifies the ATM that the request has been
approved.
 The ATM displays the successful transaction screen, ejects card and
then dispenses cash requested.
 The ATM shows the main menu to the user for selecting the next
service.

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Example - A Soft Drink
Vending Machine

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Example - A Soft Drink
Vending Machine (cont’d)

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Dynamic Modeling Techniques
Using Statechart Diagrams
 The behavior of an entity is not only a direct
consequence of its inputs, but it also depends on its
preceding state.
 The past history of an entity can best be modeled by
a finite statechart diagram traditionally named
“automata”.
 Statechart diagrams (or sometimes referred to as
state diagrams) show the different states of an entity.
 Statechart diagrams can also show how an entity
responds to various events by changing from one
state to another.

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What Is a State?
 According to Rumbaugh et al. “A state is an
abstraction of the attribute values and links of an
object. Sets of values are grouped together into a
state according to properties that affect the gross
behavior of the object.”
 For example, consider you have $100,000 in a
bank account. The behavior of the withdraw
function would be:
 balance := balance – withdrawAmount; provided that the
balance after the withdrawal is not less than $0;
 However, if the account balance becomes negative after
a withdrawal, the behavior of the withdraw function would
be quite different.

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What Is a State?(cont’d)
 There are several characteristics of states:
 A state occupies an interval of time.
 A state is often associated with an abstraction of
attribute values of an entity satisfying some condition(s).
 An entity changes its state not only as a direct
consequence of the current input, but it is also
dependent on some past history of its inputs.

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UML Notation (cont’d)
Action or activity Description
entry/ action 1; …; action n Upon entry to the state, the specified
actions are performed.
exit/ action 1; …; action n Upon exit from the state, the specified
actions are performed.
do/ activity The specified activity is performed
continuously while in this state.
event-name(parameters)
[guard-condition] / action
1 ; …; action n
An internal transition is fired when the
specified event occurs and the
specified guard condition is true. The
specified actions are performed when
the transition is fired.

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UML Notation (cont’d)
Initial state
Final state
State
History state
Junction state
Concurrent composite state
Transition

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Transition
 A transition from one state to another
takes place instantaneously in response
to some external events or internal
stimuli.

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Transition (cont’d)
 A transition is fired when the following
conditions are satisfied:
 The entity is in the state of the source state.
 An event specified in the label occurs.
 The guard condition specified in the label is
evaluated to be true.
 When a transition is fired, the actions
associated with it are executed.

Jar chapter 4, part 1

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