UML_Lecture

About myself
Yi Luo
TA for EEL5881
3rd Year Phd student in CpE
Email: [e-mail]
Office hour:
Wednesday 3:00PM-5:00PM in HEC-365

Acknowledgements
Slides material are taken from different sources including:
the slides of Mr. Shiyuan Jin’s UML class, EEL 4884, Fall 2003.
Object-Oriented and Classical Software Engineering, Sixth Edition, WCB/McGraw-Hill, 2005 Stephen R. Schach
UML resource page http://www.uml.org/

Outline
What is UML and why we use UML?
How to use UML diagrams to design software system?
What UML Modeling tools we use today?

What is UML and Why we use UML?
UML → “Unified Modeling Language”
Language: express idea, not a methodology
Modeling: Describing a software system at a high level of abstraction
Unified: UML has become a world standard
Object Management Group (OMG): www.omg.org

What is UML and Why we use UML?
More description about UML:
It is a industry-standard graphical language for specifying, visualizing, constructing, and documenting the artifacts of software systems
The UML uses mostly graphical notations to express the OO analysis and design of software projects.
Simplifies the complex process of software design

What is UML and Why we use UML?
Why we use UML?
Use graphical notation: more clearly than natural language (imprecise) and code (too detailed).
Help acquire an overall view of a system.
UML is not dependent on any one language or technology.
UML moves us from fragmentation to standardization.

What is UML and Why we use UML?

How to use UML diagrams to design software system?
Types of UML Diagrams:
Use Case Diagram
Class Diagram
Sequence Diagram
Collaboration Diagram
State Diagram
This is only a subset of diagrams … but are most widely used

Use-Case Diagrams
A use-case diagram is a set of use cases
A use case is a model of the interaction between
External users of a software product (actors) and
The software product itself
More precisely, an actor is a user playing a specific role
describing a set of user scenarios
capturing user requirements
contract between end user and software developers

Use-Case Diagrams
Library System
Borrow
Order Title
Fine Remittance
Client
Employee
Supervisor
Boundary
Actor
Use Case

Use-Case Diagrams
Actors: A role that a user plays with respect to the system, including human users and other systems. e.g., inanimate physical objects (e.g. robot); an external system that needs some information from the current system.
Use case: A set of scenarios that describing an interaction between a user and a system, including alternatives.
System boundary: rectangle diagram representing the boundary between the actors and the system.

Use-Case Diagrams
Association:
communication between an actor and a use case; Represented by a solid line.
Generalization: relationship between one general use case and a special use case (used for defining special alternatives) Represented by a line with a triangular arrow head toward the parent use case.

Use-Case Diagrams
Extend: a dotted line labeled <
> with an arrow toward the base case. The extending use case may add behavior to the base use case. The base class declares “extension points”.
<
>
Include: a dotted line labeled <
> beginning at base use case and ending with an arrows pointing to the include use case. The include relationship occurs when a chunk of behavior is similar across more than one use case. Use “include” in stead of copying the description of that behavior.
<
>

Use-Case Diagrams
Figure 16.12
The McGraw-Hill Companies, 2005

Use-Case Diagrams
Both Make Appointment and Request Medication include Check Patient Record as a subtask (include)
The extension point is written inside the base case Pay bill; the extending class Defer payment adds the behavior of this extension point. (extend)
Pay Bill is a parent use case and Bill Insurance is the child use case. (generalization)
(TogetherSoft, Inc)

Class diagram
A class diagram depicts classes and their interrelationships
Used for describing structure and behavior in the use cases
Provide a conceptual model of the system in terms of entities and their relationships
Used for requirement capture, end-user interaction
Detailed class diagrams are used for developers

Class diagram
Each class is represented by a rectangle subdivided into three compartments
Name
Attributes
Operations
Modifiers are used to indicate visibility of attributes and operations.
‘+’ is used to denote Public visibility (everyone)
‘#’ is used to denote Protected visibility (friends and derived)
‘-’ is used to denote Private visibility (no one)
By default, attributes are hidden and operations are visible.

Class diagram

OO Relationships
There are two kinds of Relationships
Generalization (parent-child relationship)
Association (student enrolls in course)
Associations can be further classified as
Aggregation
Composition

Subtype2
Supertype
Subtype1
OO Relationships: Generalization
-Inheritance is a required feature of object orientation
-Generalization expresses a parent/child relationship among related classes.
Used for abstracting details in several layers
Regular
Customer
Loyalty
Customer
Customer
Example:

Represent relationship between instances of classes
Student enrolls in a course
Courses have students
Courses have exams
Etc.
Association has two ends
Role names (e.g. enrolls)
Multiplicity (e.g. One course can have many students)
Navigability (unidirectional, bidirectional)
OO Relationships: Association

Association: Multiplicity and Roles
University
Person
1
0..1
*
*
Multiplicity
Symbol Meaning
1 One and only one
0..1 Zero or one
M..N From M to N (natural language)
* From zero to any positive integer
0..* From zero to any positive integer
1..* From one to any positive integer
teacher
employer
Role
Role
“A given university groups many people; some act as students, others as teachers. A given student belongs to a single university; a given teacher may or may not be working for the university at a particular time.”
student

Class diagram
[from UML Distilled Third Edition]

Association: Model to Implementation
Class Student {
Course enrolls[4];
}
Class Course {
Student have[];
}
Student
Course
enrolls
has
*
4

OO Relationships: Composition
Class W
Class P1
Class P2
Association
Models the part–whole relationship
Composition
Also models the part–whole relationship but, in addition, Every part may belong to only one whole, and If the whole is deleted, so are the parts
Example:
A number of different chess boards: Each square belongs to only one board. If a chess board is thrown away, all 64 squares on that board go as well.
Whole Class
Part Classes
Example
Figure 16.7
The McGraw-Hill Companies, 2005
[From Dr.David A. Workman]

OO Relationships: Aggregation
Class C
Class E1
Class E2
AGGREGATION
Container Class
Containee Classes
Bag
Apples
Milk
Example
Aggregation:
expresses a relationship among instances of related classes. It is a specific kind of Container-Containee relationship.
express a more informal relationship than composition expresses.
Aggregation is appropriate when Container and Containees have no special access privileges to each other.
[From Dr.David A. Workman]

Aggregation vs. Composition
Composition is really a strong form of association
components have only one owner
components cannot exist independent of their owner
components live or die with their owner
e.g. Each car has an engine that can not be shared with other cars.
Aggregations
may form "part of" the association, but may not be essential to it. They may also exist independent of the aggregate. e.g. Apples may exist independent of the bag.

Good Practice: CRC Card
Class Responsibility Collaborator
easy to describe how classes work by moving cards around; allows to quickly consider alternatives.

Interaction Diagrams
show how objects interact with one another
UML supports two types of interaction diagrams
Sequence diagrams
Collaboration diagrams

Sequence Diagram(make a phone call)
Caller
Phone
Recipient
Picks up
Dial tone
Dial
Ring notification
Ring
Picks up
Hello

Sequence Diagram:Object interaction
Self-Call: A message that an
Object sends to itself.
Condition: indicates when a message is sent. The message is sent only if the condition is true.
Iteration
Condition

Sequence Diagrams – Object Life Spans
Creation
Create message
Object life starts at that point
Activation
Symbolized by rectangular stripes
Place on the lifeline where object is activated.
Rectangle also denotes when object is deactivated.
Deletion
Placing an ‘X’ on lifeline
Object’s life ends at that point
Activation bar

Sequence Diagram
Sequence diagrams demonstrate the behavior of objects in a use case by describing the objects and the messages they pass.
The horizontal dimension shows the objects participating in the interaction.
The vertical arrangement of messages indicates their order.
The labels may contain the seq. # to indicate concurrency.
Message

Interaction Diagrams: Collaboration diagrams
User
Catalog
Reservations
start
1: look up
2: title data
3 : [not available] reserve title
4 : title returned
5 : hold title
6 : borrow title
6: remove reservation
5: title available
Collaboration diagrams are equivalent to sequence diagrams. All the features of sequence diagrams are equally applicable to collaboration diagrams
Use a sequence diagram when the transfer of information is the focus of attention
Use a collaboration diagram when concentrating on the classes

State Diagrams (Billing Example)
State Diagrams show the sequences of states an object goes through during its life cycle in response to stimuli, together with its responses and actions; an abstraction of all possible behaviors.
Unpaid
Start
End
Paid
Invoice created
paying
Invoice destroying

State Diagrams (Traffic light example)
Yellow
Red
Green
Traffic Light
State
Transition
Green timer expires
Yellow timer expires
Car trips sensor
Event
Start

What UML Modeling tools we use today?
List of UML tools http://en.wikipedia.org/wiki/List_of_UML_tools
ArgoUML: http://argouml.tigris.org/
Rational Rose (www.rational.com) by IBM
UML Studio 7.1 ( http://www.pragsoft.com/) by Pragsoft Corporation: Capable of handling very large models (tens of thousands of classes). Educational License US$ 125.00; Freeware version.
TogetherSoft Control Center; TogetherSoft Solo (http://www.borland.com/together/index.html) by Borland

Conclusion
UML is a standardized specification language for object modeling
Several UML diagrams:
use-case diagram: a number of use cases (use case models the interaction between actors and software)
Class diagram: a model of classes showing the static relationships among them including association and generalization.
Sequence diagram: shows the way objects interact with one another as messages are passed between them. Dynamic model
State diagram: shows states, events that cause transitions between states. Another dynamic model reflecting the behavior of objects and how they react to specific event
There are several UML tools available