1

SOFTWARE ENGINEERING II Lecture VIII- Part 2

COMSATS Institute of Information Technology Computer Science Department

Syed Faraz Ahmad,MS (Computer Science)

CIIT Abbottabadcomsian032@gmail.com

2

UML Defined

• The Unified Modeling Language (UML) is a general purpose visual modeling language that is used to specify, visualize, construct, and document the artifacts of a software system.

Source: Rumbaugh, Jacobson, Booch, Unified Modeling Language Reference Manual (Addison-Wesley, 1999), p. 3

3

UML Defined

• It captures decisions and understanding about systems that must be constructed.

• It is used to understand, design, browse, configure, maintain, and control information about systems.

• It is intended to be used with all development methods, lifecycle stages, application domains, and media.

Source: Rumbaugh, Jacobson, Booch, Unified Modeling Language Reference Manual (Addison-Wesley, 1999), p. 3

4

Goals of UML There were a number of goals behind the development

of UML: UML is a general-purpose modeling language that all

modelers can use. It is meant to include the concepts of the leading methods so

that it can be used as their modeling language. It was intended to be as familiar as possible. It is meant to support good practices for design such as

encapsulation, separation of concerns, and capture of the intent of a model construct.

It is intended to address current software development issues, such as large scale, distribution, concurrency, patterns and team development.

It was to be as simple as possible while still being capable of modeling the full range of practical systems that need to be built.

Source: Rumbaugh, Jacobson, Booch, Unified Modeling Language Reference Manual (Addison-Wesley, 1999), p. 8-9

5

UML Building Blocks

• UML is composed of three building blocks:– Things

• These are the modeling elements– Relationships

• These tie things together– Diagrams

• These are views into UML models

Source: Booch, The Unified Modeling Language User Guide (Addison-Wesley, 1998), p. 2.

6

UML Things UML thing may be partitioned into:

Structural things Represent the nouns of a UML model such as class,

component, use case, etc Behavioral things

Represent the verbs of a UML model such as interactions, states, etc.

Grouping things Represent things that group elements together such as the

package. Annotational things

The note

Source: Arlow and Neustadt, UML and the Unified Process (Addison-Wesley, 2002), p. 9.

Relationships

In UML, object interconnections (logical or physical), are modeled as relationships.

There are three kinds of relationships in UML:

• Dependencies

• Generalizations

• Associations

Dependency Relationships

CourseSchedule

add(c : Course)remove(c : Course)

Course

A dependency indicates a semantic relationship between two or more elements. The dependency from CourseSchedule to Course exists because Course is used in both the add and remove operations of CourseSchedule.

Generalization Relationships

PersonA generalization connects a subclassto its superclass. It denotes an inheritance of attributes and behaviorfrom the superclass to the subclass andindicates a specialization in the subclass of the more general superclass.Student

Generalization Relationships (Cont’d)

Student

UML permits a class to inherit from multiple superclasses, although some programming languages (e.g., Java) do not permit multiple inheritance.

TeachingAssistant

Employee

Association Relationships

If two classes in a model need to communicate with each other, there must be link between them.

An association denotes that link.

StudentInstructor instructs

Here , an association is instructs.

Association Relationships(Cont’d)

The example indicates that a Student has one or more Instructors:

InstructorStudent1..*

Association Relationships (Cont’d)

The example indicates that every Instructor has one or more Students:

InstructorStudent1..*

UML Diagram Types with ExamplesThere are 14 UML diagram types to help you model these behavior. They can be divided into two main categories structure diagrams and behavioral diagrams

Class DiagramComponent DiagramDeployment DiagramObject DiagramPackage DiagramProfile DiagramComposite Structure Diagram

Use Case DiagramActivity DiagramState Machine DiagramSequence DiagramCommunication DiagramInteraction Overview DiagramTiming Diagram

Structure diagrams show the things in a system being modeled. In a more technical term they show different objects in a system. 

Behavioral diagrams shows what should happen in a system. They describe how the objects interact with each other to create a functioning system.

http://creately.com/blog/diagrams/uml-diagram-types-examples/

Class Diagram

Class diagrams are the most used UML diagram type. It is the main building block of any object oriented solution. It shows the classes in a system, attributes and operations of each class and the relationship between each class.In most modeling tools a class has three parts, name at the top, attributes in the middle and operations or methods at the bottom. In large systems with many related classes, classes are grouped together to create class diagrams. Different relationships between classes are shown by different types of arrows.

Component Diagram

A component diagram displays the structural relationship of components of a software system.

These are mostly used when working with complex systems that has many components.

Components communicate with each other using interfaces. The interfaces are linked using connectors.

Simple Component Diagram with Interfaces

Object Diagram

Object Diagrams, sometimes referred as Instance diagrams are very similar to class diagrams.

As class diagrams they also show the relationship between objects but they use real world examples.

They are used to show how a system will look like at a given time. Because there is data available in the objects they are often used to explain complex relationships between objects.

UML Object Diagram Example

Use Case Diagram

Most known diagram type of the behavioral UML diagrams, Use case diagrams gives a graphic overview of the actors involved in a system, different functions needed by those actors and how these different functions are interacted.

It’s a great starting point for any project discussion because you can easily identify the main actors involved and the main processes of the system. 

Use Case diagram showing Actors and main processes

Activity Diagram

Activity diagrams represent workflows in an graphical way.

They can be used to describe business workflow or the operational workflow of any component in a system.

Sometimes activity diagrams are used as an alternative to State machine diagrams.

Activity Diagrams with start, end, processes and decision points

Sequence Diagram

Sequence diagrams in UML shows how object interact with each other and the order those interactions occur.

It’s important to note that they show the interactions for a particular scenario.

The processes are represented vertically and interactions are show as arrows..

Sequence Diagrams in UML shows the interaction between two processes

Communication Diagram

Communication diagram was called collaboration diagram.

It is similar to sequence diagrams but the focus is on messages passed between objects.

The same information can be represented using a sequence diagram and different objects.

Communication Diagram in UML