ict117 week08 structural modelling

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PowerPoint Presentation for Dennis, Wixom, & Tegarden Systems Analysis and Design with UML, 3rd EditionCopyright 2009 John Wiley & Sons, Inc. All rights reserved.

Structural ModelingChapter 6: Dennis, Wixom and

Tegarden


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17 March, 2011 ICT117 Systems Analysis & Design, Semester 1, 2011

Includes John Wiley & Sons Inc material

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ObjectivesUnderstand the rules and style guidelines forcreating CRC cards, class diagrams, andobject diagrams.Understand the processes used to create CRCcards, class diagrams, and object diagrams.Be able to create CRC cards, class diagrams,and object diagrams.Understand the relationship between thestructural and use case models.


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Structural ModelA formal way of representing the objects thatare used and created by a business systemPeople

Places

Things

Drawn using an iterative processFirst drawn in a conceptual, business-centric way

Then refined in a technology-centric waydescribing the actual databases and files


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STRUCTURAL MODELS


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A Common LanguageStructural models create a well-definedvocabulary shared by users and analystsClasses created during analysis are not the classes

that programmers develop during implementationThis refinement comes later

Typical structural models:CRC cards

Class (and Object) diagrams


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Classes: Attributes &Operations ClassesTemplates for instances of people,

places, or things

AttributesProperties that describe the state

of an instance of a class (an object)

OperationsActions or functions that a class

can perform


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RelationshipsDescribe how classes relate to one anotherThree basic types in UML

GeneralizationEnables inheritance of attributes and operations

AggregationRelates parts to wholes

AssociationMiscellaneous relationships between classes


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CRC CARDS

CRC = Class Responsibilities and

Collaborations


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Responsibilities &CollaborationsResponsibilities

Knowing

DoingCollaborationObjects working together to service a request

Refer page 211


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Front-Side of a CRC Card


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Back-Side of a CRC Card


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CLASS DIAGRAMS


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Elements of a Class Diagram


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Attribute VisibilityAttribute visibility can be specified in the classdiagramPublic attributes (+) are visible to all classes

Private attributes (-) are visible only to an instanceof the class in which they are defined

Protected attributes (#) are like private attributes,

but are also visible to descendant classes

Visibility helps restrict access to the attributesand thus ensure consistency and integrity


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OperationsConstructorCreates object

QueryMakes information about state available

UpdateChanges values of some or all attributes


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More Elements of ClassDiagrams


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MultiplicitiesDepartment

1

Boss

1

Employee

1

Child

0..*

Boss

1

Employee

1..*

Exactly one:

A department has one

and only one boss

Zero or more:An employee has zero

to many children

One or more:

A boss is responsible for

one or more employees


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More MultiplicitiesEmployee

1

Spouse

0..1

Employee

1

Vacation

2..4

Employee

1

Committee

1..3, 5

Zero or one:

An employee can be

married to 0 or 1 spouse

Specified range:An employee can take 2

to 4 vacations each year

Multiple disjoint ranges:

An employee can be in 1

to 3 or 5 committees


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Sample Class Diagram


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Object Diagrams


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CREATING CRC CARDS AND

CLASS DIAGRAMS


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Object IdentificationTextual analysis of use-case informationNouns suggest classes

Verbs suggest operations

Creates a rough first cutCommon object listIncidentsRoles


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7 Steps to Structural ModelsCreate CRC CardsExamine common object listsRole-play the CRC cardsCreate the class diagramReview the class diagramIncorporate patternsReview the model


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Next lectureBehavioural ModelsInteraction diagramsState MachinesCRUD analysis

ict117 week08 structural modelling

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