SE_Lec 09_ UML Behaviour Diagrams

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Structure Diagrams (Class diagrams) are used to describe

the static composition of components/Objects (i.e.,

constraints on what instances may exist at run-time).

Deployment Diagrams are used to describe the mapping

between software artifacts and deployment targets.

Why do objects exist?

To perform an activity to help fulfill a system’s purpose

What about modeling dynamic behavior?

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Interaction diagrams model how groups of object

collaborate to perform some behavior

Typically captures the behavior of a single use case

Behaviour Diagrams are used to describe the behaviour

Of the whole application.

Of a particular process in an application.

Of a specific object in an application.

The behavioral diagrams are categorized as follows:

use case diagrams,

interaction diagrams (Sequence & Communication),

state–chart diagrams, and

activity diagrams.

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Use Case: Manage Course Information (UC_ID1)

Participating Actors: Course Administrator

Entry Conditions: Course Administrator is logged into

Courseware

Exit Conditions: Course Administrator has received an

acknowledgement from the system that the selected

transaction is complete, or if not complete, a message

explaining the failure

Quality Requirements: (Performance) Course

Administrator receives a response from the system in less

than 3 seconds

Related Requirements: Create, Modify, and Delete Course

…

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Use Case: Order Entry

1) An Order Entry window sends a “prepare” message to an

Order.

2) The Order sends “prepare” to each Order Line on the

Order.

3) Each Order Line checks the given Stock Item.

4) Remove appropriate quantity of Stock Item from stock.

5) Create a deliver item.

Alternative: Insufficient Stock

3a) if Stock Item falls below reorder level then Stock Item

requests reorder

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UML Specifies a number of interaction diagrams to

model dynamic aspects of the system

Dynamic aspects of the system

Messages moving among objects/classes

Flow of control among objects

Sequences of events

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Interaction Diagrams: Set of objects or roles and the

messages that can be passed among them.

Sequence Diagrams:

• Illustrate object interactions arranged in time sequence

(Emphasize time ordering)

Communication Diagrams (Collaboration Diagram):

• Illustrate object interactions organized around the objects

and their links to each other (Emphasize structural ordering).

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Describe the flow of messages, events, actions between

objects

Show concurrent processes and activations

Show time sequences that are not easily depicted in

other diagrams

Typically used during analysis and design to document

and understand the logical flow of your system

Emphasis on time ordering!

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Objects: aStudent is a specific

instance of the Student class

Specific instance

of an Object

Generic (unnamed)

objects

Generic (unnamed) objects of

class type Seminar and Course

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Tim

e Increasin

g

All lines should be horizontal to indicate instantaneous actions.

Additionally if ActivityA happens before ActivityB, ActivityA must be

above activityB

Lower = Later!

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Execution

or

Activation Box

Life Line

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Return value

Method call

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c : Client

: Transaction

o : ODBCProxy

create()

setActions(a, b, c)setValues(a, 3, 4)

setValues(b, c, 7)

(committed)

destroy()

Synchronous message

Asynchronous message

create()

destroy()

Return message

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Synchronous message

Asynchronous message

Return messageThere are problems

here… what are they?

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Rarely use options, loops, alt/else

These constructs complicate a diagram and make them

hard to read/interpret.

Frequently it is better to create multiple simple diagrams

Create sequence diagrams for use cases when it helps

clarify and visualize a complex flow

Remember: the goal of UML is communication and

understanding

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How to construct an SSD from a use case:

1. Draw black box and a life line, for every System object

(Sub-system) include as on right side

2. For each actor that directly operates on

the System, draw a stick figure and a lifeline.

3. For each System events that each actor generates in use

case, draw a message.

4. Optionally, include use case text to left of diagram.

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Sequence diagrams model object interactions with an

emphasis on time ordering

Method call lines

Must be horizontal!

Vertical height matters! “Lower equals Later”

Label the lines

Lifeline – dotted vertical line

Execution bar – bar around lifeline when code is running

Arrows

Synchronous call (you’re waiting for a return value) – triangle

arrow-head

Asynchronous call (not waiting for a return) – open arrow-

head

Return call – dashed line

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To give an exam, an instructor first notifies the students

of the exam date and the material to be covered. She

then prepares the exam paper (with sample solutions),

gets it copied to produce enough copies for the class,

and hands it out to students on the designated time and

location. The students write their answers to exam

questions and hand in their papers to the instructor. The

instructor then gives the exam papers to the TAs, along

with sample solutions to each question, and gets them

to mark it. She then records all marks and returns the

papers to the students.

Draw a sequence diagram that represents this process.

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Objects are rectangular icons

e.g., Order Entry Window, Order, etc.

Messages are arrows between icons

e.g., prepare()

Numbers on messages indicate sequence

Also spatial layout helps show flow

Which do you prefer: sequence or collaboration diagrams?

Fowler now admits he doesn’t use collaboration diagrams

Interaction diagrams show flow clearly, but are awkward

when modeling alternatives

UML notation for control logic has changed in UML 2 but

Fowler isn’t impressed

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A statechart diagram - shows the behavior of classes in

response to external stimuli. This diagram models the

dynamic flow of control from state to state within a

system.

State machine diagram - event-ordered behavior that

specifies the sequences of states an object/instance (of

class/interface/collaboration/…/system) goes through

during its lifetime; events trigger transitions and cause

responses.

UML statecharts show states, transitions, events.

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A state diagram is a graph consisting of

States (a mode of the entity).

simple states

composite states (nested state diagrams)

State transitions connecting the states.

including events and actions.

State – Constraint or condition or situation during which an

object/instance may perform some activity; The state of

an object is characterized by the value of one or more of

its attributes.

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Start state: State transition is executed immediately

during the creation of the object.

Only possible event: create(parameter)

Java: constructor (new)

Final State: destruction of the object

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A transition connects two states and shows the flow of

control.

A transition can include a triggering event, a guard and

actions to be executed.

Transitions without event and guard are executed

immediately when an activity is finished respectively all sub

states were passed through.

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An event is a phenomenon in space and time significant

for the modeled system.

An event can appear synchronously or asynchronously.

Synchronous events:

• Call event: triggered by call

• Exception event: triggered by called object at return

Asynchronous events:

• Signal event: signal sent by other object

• Change event: triggered by side effects on object

attributes

• Time event: spontaneously triggered by Boolean guard

over time

An event can trigger state changes.

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Signals are asynchronous, i.e., the sender does not wait until

the receiver received the signal or reacted on it.

A call event is triggered by a (synchronous) operation call.

Call events are synchronous, i.e., the sender waits until the

receiver reacted on the event.

In the state automaton signals and call events are

indistinguishable from each other.

The receiver can:

ignore the event (the event is lost),

execute its trigger event or

execute an operation.

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Represents the dispatch of an operation

Name and parameter of the event must be compatible

to methods of the class.

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A time event appears after the expiration of a time

period.

A change event occurs if a specific constraint is fulfilled.

The constraint is a Boolean

Expression on the attributes of the actual object.

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Signals can be sent to other objects during a transition.

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Possible actions:

send signal

perform call

perform access

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A state can be refined hierarchically by composite

states.

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In a state several sequences of sub states described by

own state machines can be performed concurrently.

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Activity Diagram – a special kind of Statechart diagram,

but showing the flow from activity to activity (not from

state to state).

Can be attached to classes, interfaces, component nodes,

use cases, collaborations, and operations

Is similar to a Data Flow Diagram (DFD)

Activity state –non-atomic execution, ultimately result in

some action; a composite made up of other activity/action

states; can be represented by other activity diagrams

Action state –atomic execution, results in a change in state

of the system or the return of a value (i.e., calling another

operation, sending a signal, creating or destroying an

object, or some computation); non-decomposable

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action state

: CertificateOfOccupancy

[completed]

object flow

Select site

Commission architect

Develop plan

Bid plan

Do site work( ) Do trade work( )

Finish construction

initial state

sequential branch/decision

[not accepted]

[else]

final state

concurrent fork

activity state with submachine

concurrent join

triggerless transition

guard expression

optional

0..*

AND

one incoming, several outgoing

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A swimlane is a kind of package.

Every activity belongs to exactly one swimlane, but transitions may

cross lanes.

Object flow – objects connected using a dependency to the activity

or transition that creates, destroys, or modifies them

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A shorthand notation: use input pins and output pins (parameters).

Invoice inv;

inv = new Invoice;

FillOrder(inv);

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<<precondition>> Order complete

<<postcondition>> Order closed

activity

parameter

node =

object node

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Is this the same as the previous one?

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An interruptible activity region surrounds a group of actions that can

be interrupted.

The Process Order action will execute until completion, then pass

control to the Close Order action, unless a Cancel Request interrupt

is received which will pass control to the Cancel Order action.

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<<signal>>

redundant constraint

object

pin parameter

hour-glass symbol represents time

send receive

send receive

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