Software Design

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Software Design (UML)

Software Design

Static Modeling using the

Unified Modeling Language (UML)

Material based on

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Classes

ClassName

attributes

operations

A class is a description of a set of objects that share the same attributes, operations, relationships, and semantics.

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Class Names

ClassName

attributes

operations

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Class Attributes

Person

name : String address : Address birthdate : Date ssn : Id

An attribute is a named property of a

class that describes the object being modeled. In the class diagram, attributes appear in

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Class Attributes (Cont’d)

Person

name : String address : Address birthdate : Date / age : Date ssn : Id

Attributes are usually listed in the form:

attributeName : Type

A derived attribute is one that can be computed from other attributes, but doesn’t actually exist. For example, a Person’s age can be computed from his birth date. A derived attribute is designated by a preceding ‘/’ as in:

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Class Attributes (Cont’d)

Person

+ name : String # address : Address # birthdate : Date / age : Date - ssn : Id

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Class Operations

Person

name : String address : Address birthdate : Date ssn : Id

eat sleep work play

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Class Operations (Cont’d)

PhoneBook

newEntry (n : Name, a : Address, p : PhoneNumber, d : Description) getPhone ( n : Name, a : Address) : PhoneNumber

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Depicting Classes

Person

name : String birthdate : Date ssn : Id

eat() sleep() work() play()

When drawing a class, you needn’t show attributes and operation in every diagram.

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Class Responsibilities

A class may also include its responsibilities in a class diagram.

A responsibility is a contract or obligation of a class to perform a particular service.

SmokeAlarm

Responsibilities

-- sound alert and notify guard station when smoke is detected.

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Relationships

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

There are three kinds of relationships in UML:

• dependencies

• generalizations

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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

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Generalization Relationships

Person

A generalization connects a subclass to its superclass. It denotes an

inheritance of attributes and behavior from the superclass to the subclass and indicates a specialization in the

subclass

of the more general superclass. Extended by

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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

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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.

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Association Relationships (Cont’d)

We can indicate the multiplicity of an association by adding

multiplicity adornments to the line denoting the association.

The example indicates that a Student has one or more

Instructors:

Instructor Student

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Association Relationships (Cont’d)

The example indicates that every Instructor has one or more

Students:

Instructor Student

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Association Relationships (Cont’d)

We can also indicate the behavior of an object in an association (i.e., the role of an object) using rolenames.

Instructor Student

1..* 1..*

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Association Relationships (Cont’d)

We can also name the association.

Team

Student membership

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Association Relationships (Cont’d)

We can specify dual associations.

Team Student

member of 1..*

president of

1 _1..*

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Association Relationships (Cont’d)

We can constrain the association relationship by defining the

navigability of the association. Here, a Router object requests services from a DNS object by sending messages to (invoking the operations of) the server. The direction of the association indicates that the server has no knowledge of the Router.

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Association Relationships (Cont’d)

Associations can also be objects themselves, called link classes

or an association classes.

Warranty Product

Registration modelNumber

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Association Relationships (Cont’d)

A class can have a self association.

LinkedListNode

Association Relationships (Cont’d)

We can model objects that contain other objects by way of special associations called aggregations and compositions.

An aggregation specifies a whole-part relationship between an aggregate (a whole) and a constituent part, where the part can exist independently from the aggregate. Aggregations are denoted by a hollow-diamond adornment on the association. Has, Owns

Car

Engine

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Association Relationships (Cont’d)

A composition indicates a strong ownership and coincident lifetime of parts by the whole (i.e., they live and die as a whole). Compositions are denoted by a filled-diamond adornment on the association.

Window Scrollbar Titlebar Menu 1 1 1 1 1

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Groups

• Whenever we create a subclass, we are

defining a new group of objects, that is a

subset of the superclass’ group

• To be even more complete, when we define

inheritance, we usually use keywords to

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Overlapping/Disjoint Groups

• Overlapping/Disjoint

– Overlapping: Groups are overlapping if there

are objects that are members of both groups.

– Disjoint: Groups are disjoint if there are no

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Overlapping Groups

• Overlapping/Disjoint

– Example: Say we have a superclass called

‘Movie’

– Say we have two subclasses of ‘Movie’ called

‘Comedy’ and ‘Action’

– Since it is possible for a movie to have both

action and comedy, the two groups are

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Overlapping Groups

Comedy Action

Movies

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Disjoint Groups

• Overlapping/Disjoint

– Example: Say we have a superclass called

‘Book’

– Say we have two subclasses of ‘Book’ called

‘Paperback’ and ‘Hardcover’

– Since a book is either a paperback or a

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Disjoint Groups

Book

Paperback Hardcover

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Disjoint Groups

Hardcover Paperback

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Complete/Incomplete Groups

• Complete/Incomplete

– Complete: The groups listed contain all

possible objects that belong to the superclass’

group

• I.e. No more disjoint subclasses can be defined

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Complete Groups

• Complete/Incomplete

– Example: Consider our superclass ‘Book’ with

its subclasses ‘Hardcover’ and ‘Paperback’

– Are there any other kinds of book?

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Complete Groups

Book

Paperback Hardcover

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Complete Groups

Hardcover _Paperback

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Incomplete Groups

• Complete/Incomplete

– Example: Consider our superclass ‘Movie’ with

its subclasses ‘Comedy’ and ‘Action’

– Are there any other kinds of movie?

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Incomplete Groups

Movie

Comedy Action

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Incomplete Groups

Action

Movies

Comedy

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Interfaces

An interface is a named set of

operations that specifies the behavior of objects without showing their inner structure. It can be rendered in the

model by a one- or two-compartment rectangle, with the stereotype

<<interface>> above the interface name.

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Interface Services

Interfaces do not get instantiated. They have no attributes or state. Rather, they specify the services offered by a related class.

<<interface>> ControlPanel

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Interface Realization Relationship

<<interface>> ControlPanel

VendingMachine

A realization relationship connects a class with an interface that supplies its

behavioral specification. It is rendered by a dashed line with a hollow triangle towards the specifier.

specifier

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Interfaces

A class’ interface can also be rendered by a circle

connected to a class by a solid line.

File

outputStream inputStream

FileWriter

{file must not be locked}

FileReader

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Class Diagram for Univ. Courses

Department Course Professor Instructor Adjunct 1..* 1..* offers 0..3 1 teaches

1..* assigned to 1..* 0..1

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Software Design (UML) 45

School Department

Student Subject Instructor

1…* * member * 1..5 attends 1..3 1..* teaches 1..* 1 1 _1..* has 1..* 1..* assignedTo offeres

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