1. CompSci 280 S2 2107 Introduction to Software Development
UML

2. Today’s Agenda Topics: Reading: Introduction Activity Diagram
Object interaction diagrams
Sequence Diagram
Reading:
Booch G.,The Unified Modeling Language User Guide, ch 19.
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3. UML Unified Modeling Language (UML)
When creating complex OO systems, where do we start?
When building complex systems, it might be worthwhile to plan things out before you start coding!
When building a house, we usually have a set of plans.
The UML is a standard notation for writing software blueprints
UML is a language which allows us to graphically model an OO system in a standardised format.
This helps us (and others!) understand the system.
There are many different UML diagrams, allowing us to model designs from many different viewpoints. Roughly, there are
Structure diagrams (documenting the architecture), e.g. class diagrams
Behaviour diagrams (documenting the functionality), e.g. use-case diagrams
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4. 1.Introduction UML Diagrams
State
Diagrams
diagrams
The UML is used to construct a model of a software system
A model is a simplification of reality
A model is thus an abstraction that exposes interesting properties while suppressing unnecessary detail
A UML model comprises different diagrams, each focusing on a particular aspect of a system
State
Diagrams
Class
diagrams
State
Diagrams
Use case
diagrams
State
Diagrams
Activity
diagrams
Model
Component
Diagrams
Deployment
diagrams
State
Diagrams
Interaction
diagrams
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5. 1.Introduction UML diagram types
Activity diagrams, which show the activities involved in a process or in data processing .
Use case diagrams, which show the interactions between a system and its environment.
Sequence diagrams, which show interactions between actors and the system and between system components.
Class diagrams, which show the object classes in the system and the associations between these classes.
State diagrams, which show how the system reacts to internal and external events.
perspective
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6. 6 Lecture09 Borrower Reserve book Borrow copy of book
Return copy of book
Update catalogue
Librarian
A Use Case diagram is user-centered and identifies system users (actors) and tasks.
A Class diagram shows the static structure of a system in terms of classes, interfaces and their relationships.
: LibraryMember
theCopy : Copy
borrow( theCopy )
: Book
okToBorrow
borrow
borrowed
An Interaction (sequence) diagram is concerned with dynamic behaviour and shows how objects exchange messages to fulfil a task.
Not borrowable
Borrowable
returned( )
borrowed( ) [not last copy]
borrowed( ) [last copy]
A State diagram shows the states and transitions for an instance of particular class (Book in this case).
: PC
: Server
servlet
browser
dbms
<<http>>
Internet
LAN
A Deployment diagram shows the deployment of software to hardware entities. 6
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7. 1.Introduction Tool Support: ArgoUML?
You will draw some class diagrams and use-case diagrams. Options:
ArgoUML
Supports forward- and reverse-engineering.
Class diagrams  Java skeletons. Java classes  class diagrams.
Not on lab image – you’ll have to download and unzip the binary distribution in your echome directory (or on your USB pendrive) then double-click on argouml.jar (this is an “executable jarfile”).
Any general-purpose drawing package (e.g. Visio)
By hand:
This is your only option during exams and tests
You’ll have to scan your drawings into your assignments (which are submitted online)
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8. 2.Activity Diagram
Activity diagrams describe the workflow behavior of a system. 
The diagrams describe the state of activities by showing the sequence of activities performed. 
they can show activities that are conditional or parallel.
Activity diagrams do not give detail about how objects behave or how objects collaborate.
An activity is an ongoing, though interruptible, execution of a step in a workflow (such as an operation or transaction)
Represented with a rounded rectangle.
Text in the activity box should represent an activity (verb phrase in present tense).
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9. 2. Activity Diagram How to Draw an Activity Diagram
Diagrams are read from top to bottom and have branches and forks to describe conditions and parallel activities. 
A fork is used when multiple activities are occurring at the same time. 
A branch describes what activities will take place based on a set of conditions. 
All branches at some point are followed by a merge to indicate the end of the conditional behavior started by that branch. 
After the merge all of the parallel activities must be combined by a join before transitioning into the final activity state.   
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10. 2.Activity Diagram Activity Diagram Example
Fork
Branch
Start State
Merge
Join
Activity
End State
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11. 3.Object Interaction Diagrams
Object interaction diagrams show how class instances behave in terms of sending messages to one another
This interactive behavior is represented in UML by two diagrams known as Sequence diagram and Collaboration diagram. The basic purpose of both the diagrams are similar.
In UML, a sequence diagram is a popular form of interaction diagram where messages are time-ordered
Interaction diagrams give a dynamic view of objects and show how they interact at run-time to fulfil a task
Often used to model the way a use case is realized through a sequence of messages between objects.
The purpose of Interaction diagrams is to:
Model interactions between objects
Assist in understanding how a system (a use case) actually works
Verify that a use case description can be supported by the existing classes
Identify responsibilities/operations and assign them to classes
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12. 3.Object Interaction Diagrams Interaction diagram notation
Key elements of interaction diagrams are objects and messages (method calls)
Active Objects
“Life line” appears below active objects to indicate their lifespan
Messages
Arrowed lines that indicated communication between objects
Notations:
An instance, named “object”, of an unspecified class
An instance, named “object”, of a class named “Class”
An unnamed instance of class “Class”
Message m
Message reply r (optional)
Object lifeline Focus of control (optional)
object
object : Class
: Class m r
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13. 4.Sequence Diagram Objects & Messages
an Order Line
Objects:
An object in a sequence diagram is rendered as a box with a dashed line descending from it. The line is called the object lifeline, and it represents the existence of an object over a period of time.
Messages
Messages are rendered as horizontal arrows being passed from object to object as time advances down the object lifelines. Conditions ( such as [check = “true”] ) indicate when a message gets passed
Return:
This arrow indicates a return from a previous message, not a new message.
an Order Line
a Stock Item
[check = “true”] remove()
check()
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14. 4.Sequence Diagram Example:
Time Increasing -->
All lines should be horizontal to indicate instantaneous actions. Additionally if ActivityA happens before ActivityB, ActivityA must be above activity A
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15. 4.Sequence Diagram Iterations
an Order
a Order Line
Iteration:
An iteration marker, such as * (as shown), or *[i = 1..n] , indicates that a message will be repeated as indicated.
* prepare()
Iteration
marker
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16. Condition Object Message Iteration Self-Delegation Return Creation
an Order Entry window
an Order
an Order Line
a Stock Item
A Reorder Item
A Delivery Item
new
[check = “true”] new
[needsToReorder = “true”]
needsToReorder()
[check = “true”] remove()
check()
* prepare()
prepare()
Object
Message
Iteration
Return
Creation
Condition
Self-Delegation
[Fowler,97]
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17. 5. Examples: Part of a Vending Machine
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18. Banking task: applying interest to a savings account
Points to note:
Sequence diagrams are time- ordered
Actual arguments can include literals or references to participating objects
driver
: Customer
: SavingsAccount
balance :
Money
accounts( )
applyInterest( )
multiply( 0.08 )
create( )
interest :
Money
interest
add( interest )
create( )
newBalance :
Money
newBalance
create( Transaction.INTEREST, interest, this )
: Transaction
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19. Sequence Diagram Exercise: ATM Machine
Draw a sequence diagram on cash withdrawal from ATM
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