Uml Class Diagram

UML CLASS DIAGRAMS AND Dr. Hoang Huu Hanh, OST – Hue University PACKAGES hanh-at-hueuni.edu.vn

Hue University

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Agenda What

is a Class Diagram? Essential Elements of a UML Class Diagram Packages and Class Diagrams Analysis Classes Approach Tips Object and Class Constructing

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What is a Class Diagram? A

class diagram describes the types of objects in the system and the various kinds of static relationships that exist among them ◦ A graphical representation of a static view on static elements

A

central modeling technique that is based on object-oriented principles The richest notation in UML UML Class Diagrams

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Essential Elements Class Attributes Operations Relationships

◦ ◦ ◦ ◦

Associations Generalization Dependency Realization

Constraint

Rules and Notes UML Class Diagrams

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Classes A

class is the description of a set of objects having similar attributes, operations, relationships and behavior. Class Name

W in d o w Attributes

size: Size visibility: boolean

Operations

display() hide()

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Associations A

semantic relationship between two or more classes that specifies connections among their instances. A structural relationship, specifying that objects of one class are connected to objects of a second (possibly the same) class. Example: “An Employee works in a department of a Company” E m p lo y ee

D e p a rtm e nt

C om pa ny

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Associations (cont.) An

association between two classes indicates that objects at one end of an association “recognize” objects at the other end and may send messages to them. ◦ This property will help us discover less trivial associations using interaction diagrams.

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Associations (cont.) Role name Association name

S ta ffM e m instructor 1..* ber Multiplicity

instructs

*

S tu d e n t Role

Navigable ( uni - directional ) association

*

Courses Reflexive association

pre requisites 0..3

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Associations (cont.) To

clarify its meaning, an association may be named. ◦ The name is represented as a label placed midway along the association line. ◦ Usually a verb or a verb phrase.

A

role is an end of an association where it connects to a class. ◦ May be named to indicate the role played by the class attached to the end of the association path.  Usually a noun or noun phrase Mandatory for reflexive associations UML Class Diagrams

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Associations (cont.) Multiplicity

◦ The number of instances of the class, next to which the multiplicity expression appears, that are referenced by a single instance of the class that is at the other end of the association path. ◦ Indicates whether or not an association is mandatory. ◦ Provides a lower and upper bound on the number of instances.

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Associations (cont.) ◦ Multiplicity Indicators Exactly one

1

Zero or more (unlimited)

* (0..*)

One or more

1..*

Zero or one (optional association)

0..1

Specified range

2..4

Multiple, disjoint ranges

2, 4..6, 8

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Aggregation A

special form of association that models a whole-part relationship between an aggregate (the whole) and its parts.

Car

◦ Models a “is a part-part of” relationship. 2..* 1..* Door

W h o le

House

Pa rt

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Aggregation (cont’d)  Aggregation

tests:

◦ Is the phrase “part of” used to describe the relationship? A door is “part of” a car

◦ Are some operations on the whole automatically applied to its parts? Move the car, move the door.

◦ Are some attribute values propagated from the whole to all or some of its parts? The car is blue, therefore the door is blue.

◦ Is there an intrinsic asymmetry to the relationship where one class is subordinate to the other? UML Class Diagrams

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Composition A

strong form of aggregation ◦ The whole is the sole owner of its part. The part object may belong to only one whole

◦ Multiplicity on the whole side must be zero or one. ◦ The life time of the part is dependent upon the whole. The composite must manage the creation and destruction of its parts. C ircle Polygon

1

Point 3..*

Circle

Point

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Generalization Indicates

that objects of the specialized class (subclass) are substitutable for objects of the generalized class (super-class). ◦ “is kind of” relationship.

{abstract} is a

Shape tagged value thatAn abstract class {abstract} indicates that the class is abstract. Generalization relationship The name of an abstract class Circle should be italicized

Super Class

Sub Class

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Generalization A

sub-class inherits from its super-class ◦ Attributes ◦ Operations ◦ Relationships

A

sub-class may ◦ Add attributes and operations ◦ Add relationships ◦ Refine (override) inherited operations

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A

generalization relationship may UML Class Diagrams

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Dependency A

dependency indicates a semantic relation between two classes although there is no explicit association between them. A stereotype may be used to denote the type of the dependency. <> Ite ra to r

V e cto r

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Realization A

realization relationship indicates that one class implements a behavior specified by some interface An interface can be realized by many classes A class may realize many < interfaces

Lin ke d List

>

List

LinkedList

Lis t

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Constraint Rules and Notes Constraints

and notes annotate among other things associations, attributes, operations and classes. Constraints are semantic restrictions noted as Boolean Customer 1 * may be expressions. Order id: long { value > 0 }

{ total < $50 }

Constraint

canceled

Note

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TVRS Example TrafficPoliceman 1 issues *

TrafficReport id : long description : String occuredAt : Date

Offender 1..*

1

name : String id : long

reports of 1..* Policeman id : long name : String rank : int

Violation id : long description : String

<>

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UML Packages A

package is a general purpose grouping mechanism. Commonly used for specifying the logical architecture of the system. A package does not necessarily translate into a physical subN am e system.

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UML Packages (cont’d) Emphasize

the logical structure of the system (High level view) Higher level of abstraction over classes. Aids in administration and coordination of the development process.

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Packages and Class Diagrams Add

package information to class diagrams A F E

D

B

G C

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Packages and Class Diagrams Add

package information to class diagrams

b

a b.a b.a.F

a.A

b.b b.b.E

b.b.D

a.B

b.a.G a.C

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Analysis Classes A

technique for finding analysis classes which uses three different perspectives of the system:  The boundary between the system and its actors The information the system uses The control logic of the system

 

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Boundary Classes Models

the interaction between the system’s surroundings and its inner workings User interface classes ◦ Concentrate on what information is presented ◦ Don’t concentrate on visual asspects ◦ Example: ReportDetailsForm System

/ Device interface classes

◦ Concentrate on what protocols must be defined. UML Class Diagrams the ◦ Don’t concentrate on how

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Entity Classes Models

the key concepts of the system Usually models information that is persistent Can be used in multiple behaviors Example: Violation, Report, Offender.

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Control Classes Controls

and coordinates the behavior of the system Delegates the work to other classes Control classes decouple boundary and entity classes Example: ◦ EditReportController ◦ AddViolationController UML Class Diagrams

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TVRS Example R eportD etails F orm 1 <>

1

Of f enders D BProx y <> Of f enders D B

EditR eportC ontroller <> C lerk C onf irm ationD ialog 1 <>

1 1

Polic em anD BProx y <> Polic em enD B

Traf f ic R eport

Violation

Of f ender

Traf f ic Polic em an

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Object and Class Constructing

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Objectives Provide

guidelines on how to determine the classes/objects in the system

 Define

class/object structuring criteria

 

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Categorization of Application Classes

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External Classes and Interface Classes External

classes are classes that are external to the system and that interface to the system.

 Interface

(boundary) classes are classes internal to the system that interface to the external classes.



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Categorization of External Classes

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Identifying Interface Classes  Each

of the external classes interfaces to an interface class in the system. ◦

◦ An external user class interfaces to a user interface class ◦ An external system class interfaces to a system interface class ◦ An external input device class interfaces to an input device interface class ◦ An external output device class interfaces to an output device interface class ◦ An external I/O device class interfaces to an I/O device interface class ◦ An external timer class interfaces to an internal timer class

◦

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Banking System: External Classes and Interface Classes

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Entity Classes Store

information

 Often

mapped to relational database during design

Control Classes A

control class provides the overall coordination for execution of a use case.



 Makes

overall decision



 Control

objects decides when, and in what order, other objects participate in use case ◦ Interface objects ◦ Entity objects

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Kinds of Control Classes Coordinator

class

◦ Provides sequencing for use case ◦ Is not state dependent 

State

dependent control class

◦ Defined by finite state machine 

Timer

class

◦ Activated periodically

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Example: Coordinator Object

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Example: State Dependent Control Object

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Example: Timer Object

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Application Logic Classes Business

logic class

◦ Defines business-specific application logic (rules) for processing a client request ◦ Usually accesses more that one entity object 

Algorithm

class

◦ Encapsulates algorithm used in problem domain ◦ More usual in scientific,

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Example: Business Logic Object

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Example: Algorithm Object

Tips Don’t

try to use all the various notations. Don’t draw models for everything, concentrate on the key areas. Draw implementation models only when illustrating a particular implementation technique.

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Note: Unifying Concepts classifier-instance

dichotomy

◦ e.g. an object is an instance of a class OR a class is the classifier of an object specification-realization

dichotomy ◦ e.g. an interface is a specification of a class OR a class is a realization of an interface analysis-time

vs. design-time vs. Behavioral Modeling with UML

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