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Software Design

Software Design (UML)

Static Modeling using the

Unified Modeling Language

(UML)

Material based on [Booch99, Rambaugh99, Jacobson99, Fowler97, Brown99]

Classes

Software Design (UML)

ClassName

attributes

operations

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

Graphically, a class is rendered as a rectangle, usually including its name, attributes, and operations in separate, designated compartments.

Class Attributes

Software Design (UML)

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 the second compartment just below the name-compartment.

Class Attributes (Cont’d)

Software Design (UML)

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:

/ age : Date

Class Operations

Software Design (UML)

Person

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

eat sleep work play

Operations describe the class behavior and appear in the third compartment.

Class Operations (Cont’d)

Software Design (UML)

PhoneBook

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

You can specify an operation by stating its signature: listing the name, type, and default value of all parameters, and, in the case of functions, a return type.

Class Responsibilities

Software Design (UML)

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.

-- indicate battery state

Relationships

Software Design (UML)

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

There are three kinds of relationships in UML:

• dependencies
• generalizations
• associations

Generalization Relationships

Software Design (UML)

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. Student

Generalization Relationships (Cont’d)

Software Design (UML)

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 (Cont’d)

Software Design (UML)

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 :

Student (^) Instructor 1..*

Association Relationships (Cont’d)

Software Design (UML)

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

Student (^) Instructor 1..*

Association Relationships (Cont’d)

Software Design (UML)

We can also name the association.

Student (^) Team

membership 1..* 1..*

Association Relationships (Cont’d)

Software Design (UML)

We can specify dual associations.

Student Team

member of 1..*

(^1) president of 1..*