02 object modeling technique

8/17/2019 02 Object Modeling Technique

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Copyright Irwin/McGraw-Hill 19982

Object Modeling

System Concepts for Object Modeling

Objects, Attributes, Methods, and Encapsulation The objectoriented approach to system de!elopment is based on

the concept of objects that exist within a system"s en!ironment.

#bjects are e!erywhere $ebster"s %ictionary definition of an object.

Something that is or is capable of being seen, touched, or

otherwise sensed.

&n objectoriented approaches to systems de!elopment the

definition of an object is as follows' n object is something that is or is capable of being seen,

touched, or otherwise sensed, and about which users store data

and associate beha!ior.




Object Modeling


Objects, Attributes, Methods, and Encapsulation The types of objects may include a person, place, thing , or event .

n employee, customer, !endor, and student are examples of

person objects. particular warehouse, regional office, building, and room are

examples of place objects.

product, !ehicle, equipment, !ideo tape, or a window

appearing on a users display monitor are examples of thing

objects. n order, payment, in!oice, application, registration, and

reser!ation are examples of event objects.




Object Modeling


Objects, Attributes, Methods, and Encapsulation &n the objectoriented circles, the term data* refers to what are

called attributes.

Attributes are the data that represent characteristics of interestabout an object.

+xample attributes for the person object called customer'• -T#/+0 -/+0, 3&0T /+, 4T /+, 5#/+

%%0+, $#06 %%0+, T78+ #3 -T#/+0, 5#/+ 85#+,

$#06 85#+, 0+%&T 4&/&T, 9&44+ 0+%&T, #-T

4+, and #-T TT-. +ach indi!idual customer object is referred to as an object

instance.

• n instance (or object instance) of an object consists of the !alues

for the attributes that describe a specific person, place, thing, or

e!ent.




Object Modeling


Objects, Attributes, Methods, and Encapsulation $hat is the behavior * of an object.

Behavior refers to those things that the object can do and

which correspond to functions that act on the object"s data (orattributes).

&n objectoriented circles, an object"s beha!ior is commonly

referred to as a method or service.

n object is solely responsible for carrying out any functions

or beha!iors that act upon its own data (or attributes).• 3or example, only 7#- (an object) may 5:+ (beha!ior)

your 4T /+ and 5#/+ %%0+ (attributes about you).




Object Modeling


Objects, Attributes, Methods, and Encapsulation Encapsulation, an important concept.

Encapsulation is the pac;aging of se!eral items together into

one unit. oth attributes and beha!ior of the object are pac;aged

together.

The only way to access an object<s attributes is through that

object"s beha!iors.

o other object may perform that object"s beha!ior.


http://slidepdf.com/reader/full/02-object-modeling-technique 7/50Copyright Irwin/McGraw-Hill 19987

Object Modeling


Classes, enerali!ation, and "peciali!ation n important concept of object modeling is the concept of

categori=ing objects into classes.

class is a set of objects that share common attributes and beha!ior. class is sometimes referred to as an object class.

3or example, textboo; and wor;boo; objects represent thing

objects that ha!e some similar attributes and beha!ior and

could be classified as ##6s .

class may also ha!e subclasses of objects. 3or example, T-%+T and T+5+0 object classes could

be members of the class 8+0#.



Object Modeling


Classes, enerali!ation, and "peciali!ation $hen le!els of classes are identified, the concept of inheritance is

applied.

#nheritance means that methods and>or attributes defined in anobject class can be inherited or reused by another object class.

The approach that see;s to disco!er and exploit the commonalties

between objects>classes is referred to as

generalization/specialization.

enerali!ation$speciali!ation is a technique wherein theattributes and beha!iors that are common to se!eral types of an

object classes are grouped into their own class, called a

supertype. The attributes and methods of the supertype object

class are then inherited by those object classes.



Object Modeling


Classes, enerali!ation, and "peciali!ation $hen le!els of classes are identified, the concept of inheritance is

applied.

#nheritance means that methods and>or attributes defined in anobject class can be inherited or reused by another object class.

&n the object class 8+0#, T-%+T and T+5+0 example,

8+0# is referred to as a supertype (or generali=ation class)

whereas T-%+T and T+5+0 are referred to as subtypes (or

speciali=ation class ). class supertype is an entity whose instances store attributes

that are common to one or more class subtypes.

class subtype is an object class whose instances inherit some

common attributes from a class supertype, and then add other

attributes that are unique to an instances of the subtype.



Object Modeling


Classes, enerali!ation, and "peciali!ation The class supertype will ha!e one or more one-to-one relationships

to object class subtypes.

These relationships are sometimes called & * relationships(or $ *, or #-4% + *) because each instance of

the supertype is also an* instance of one or more subtypes.

-sing #/T notation, classes are represented on an object model

as a rectangle.

The rectangle is di!ided into three portions.• The top portion contains the name of the class.

• The middle portion contains the name of the common attributes of

interest.

• The lower portion contains the common beha!ior (or methods).



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Object Modeling

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Object Modeling


Object$Class %elationships #bjects and classes do not exist in isolation.

The things they represent interact with, and impact one another

to support the business mission. Thus there is an object>class relationship.

• n object$class relationship is a natural business association that

exists between one or more objects>classes.

3or example, consider the object classes customer and order

that may exist in a typical information system and how theyinteract.

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14

Object Modeling


Object$Class %elationships $e graphically illustrate the association(relationship) between two

classes as a connecting line.

!erb phrase describes the relationship. ll relationships are implicitly bidirectional, meaning that they

can interpreted in both directions.

$hat is multiplicity?

Multiplicity defines the minimum and maximum number of

occurrences of one object>class for a single occurrence of therelated object>class.

ecause all relationships are bidirectional, multiplicity must

be defined in both directions for e!ery relationship.



15

Object Modeling

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Object Modeling


Object$Class %elationships $hat are aggregation class relationships?

ometimes objects>classes are made up of other objects>classes.

This type of relationship is called aggregation.• &t is also sometimes referred to as wholepart* or partof*

relationships.

3or example, the T+@T##6 object may contain se!eral

objects, including' #9+0, T4+ #3 #T+T,

58T+0, and &%+@ objects.

• The 58T+0 object contains 8:+ objects, which in turn

contain 80:085 objects, which in turn contain $#0%

objects, and so forth.




Object Modeling


Object$Class %elationships y identifying aggregation relationships we can partition a !ery

complex object and assign beha!iors and attributes to the

indi!idual objects within it.

/ultiplicity is also specified for aggregate relationships.




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Object Modeling


Messages and Message "ending #bjects>lasses interact or AcommunicateA with one another by

passing messages.

message is passed when one object in!o;es another object<smethod (beha!ior) to request information or some action

n object sending a message does not need to ;now how the

recei!ing object is organi=ed internally or how the beha!ior is to

be accomplished, only that it responds to the request in a well

defined way.




Object Modeling


Messages and Message "ending 8olymorphism $hat is it?

&olymorphism means many forms*. pplied to object

oriented techniques, it means that a beha!ior may be completeddifferently for different objects>classes.

The requesting object ;nows the what ser!ice (or beha!ior) to

request and from which object. 5owe!er, the requesting object

does not need to worry about how a beha!ior is accomplished.




Object Modeling

#$e %rocess of Object Modeling

&er'orming Object Oriented Analysis (OOA) The purpose of ## is to gain a better understanding of the

system and its functional requirements.

## requires that we identify the objects, their data attributes,associated beha!ior, and relationships which support the required

business system functionality.

$e perform object modeling to document the identified objects,

the data and beha!ior they encapsulate, plus their relationships

with other objects.

Two general acti!ities when performing object oriented analysis'

3inding and identifying the business objects.

#rgani=ing the objects and identifying their relationships.




Object Modeling


inding And #denti'ying he Business Objects &n trying to identify objects, many methodology experts

recommend the technique of searching the requirements document

or other associated documentation and underline the nouns which

may represent potential objects.

This could be a monumental tas;B There are just too many

nouns.

#ne of the more popular and successful approaches for finding

and identifying objects, is a technique called *se Case Modeling

de!eloped by %r. &!ar Cacobson.

*se Case Modeling is the process of identifying and modeling

business e!ents, who initiated them, and how the system

responds to them.




Object Modeling


inding And #denti'ying he Business Objects -se case modeling brea;s down the entire scope of system

functionality into many smaller statements of system functionality

called use cases or business e!ents.

use case a beha!iorally related sequence of steps (a

scenario), both automated and manual for the purpose of

completing a single business tas;.

This smaller format simplifies and ma;es more efficient the

technique of underlining the nouns.

&t identifies and describes the system functions from the

perspecti!e of external users.




Object Modeling


inding And #denti'ying he Business Objects -se ases are initiated by users or systems called Actors.

n actor represents anything that needs to interact with the

system to exchange information. n actor is a user, a role,which could be an external system as well as a person.

• n actor initiates system acti!ity, a use case, for the purpose of

completing some business tas;.

• n actor represents a role fulfilled by a user interacting with the

system and is not meant to portray a single indi!idual or job title.

• 3or e!ents that are triggered by time called temporal events, the

actor is the system itself.




Object Modeling


inding And #denti'ying he Business Objects -se cases pro!ide the following benefits'

s a basis to help identify objects and their high le!el

relationships and responsibilities. !iew of system beha!ior from external person"s !iewpoint.

n effecti!e tool for !alidating requirements.

n effecti!e communication tool.

s a basis for a test plan.

s a basis for a user"s manual.




Object Modeling


inding And #denti'ying he Business Objects tep 1' &dentifying ctors and -se ases.

good place to find potential actors and use cases is by

analy=ing the context model diagram of the system.• &f an external party initiates the input, it is considered an actor.

• ome of the inputs are self explanatory, but others may be

misleading, it is always wise to confirm your findings with the

system"s business analyst.




Object Modeling

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Member "ervices

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Object Modeling

AC)O% *"E CA"EClub Member initiates "ubmit &romotion Order

"ubmit %egular Order

&otential Member initiates "ubmit /e0 "ubscription

&ast Member initiates "ubmit "ubscription %ene0al

Member "ervices epartment initiates %e1uest Membership %pts2

Mar,eting epartment initiates Create /e0 Monthly &romotion

Create /e0 "easonal &romotionCreate /e0 "ubscription &rogram

%e1uest &romotion %pts2

%e1uest "ales %pts2

Member "ervices "ystem initiates "end /e0 "ubscription O''er

"end Club &romotion

"end "ubscription %ene0al O''er




Object Modeling


inding And #denti'ying he Business Objects tep 2' onstructing a -se ase /odel

*se Case Model iagram is used to graphically depict the

system scope and boundaries in terms of use cases and actors.

The use case model diagram represents the relationships

between the actors and use cases defined for each business

subsystem.

• The subsystems represent logical functional areas of business

processes.

• The partitioning of system beha!ior into subsystems is !ery

important in understanding the system architecture and is !ery ;ey

to defining your de!elopment strategy E which use cases will be

de!eloped first and by who.




Object Modeling

Member

Services

Department

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Department

Member

Services

System

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Potential

Member

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Member

Create New

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Request Promotion

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rder

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embers$ipSubsystem




Object Modeling


inding And #denti'ying he Business Objects tep F' %ocumenting the -se ase ourse of +!ents

3or each use case identified, use case"s normal course of e!ents

must be documented.

use case"s normal course of e!ents is a step by step

description starting with the actor initiating the use case until

the end of the business e!ent.

• t this point we only include the major steps which happen the

majority of the time (its normal course).

• +xception conditions or conditional branching logic will be

documented in a later step.




Object Modeling*"E CA"EAuthor34452 Bentley4 ate34467$76$894

*"E CA"E /AME3 ubmit 8romotion #rder

AC)O%3 lub /ember

E"C%#&)#O/3 %escribes the process when a club member submits a club promotion order to either

indicate the products they are interested in ordering or declining to order duringthis promotion.

/O%MA5

CO*%"E3

1. This use case is initiated when the club member submits the promotion order to

be processed.

2. The club member"s personal information such as address is !alidated against

what is currently recorded in member ser!ices.

F. The promotion order is !erified to see if product is being ordered.

G. The club member"s credit status is chec;ed with (ccounts 0ecei!able to ma;esure no payments are outstanding.

H. 3or each product being ordered, !alidate the product number.

I. 3or each product being ordered, chec; the a!ailability in in!entory and record

the ordered product information which include )quantify being ordered* and

gi!e each ordered product a status of )open*.

J. reate a 8ic;ing Tic;et for the promotion order containing all ordered

products which ha!e a status )open*.

K. 0oute the 8ic;ing Tic;et to the $arehouse.

&%E-CO/#)#O/3 -se case Send Club Motion has been processed.

&O")-CO/#)#O/3 8romotion order has been recorded and the 8ic;ing Tic;et has been routed to the

$arehouse.

A""*M&)#O/"3




Object Modeling


inding And #denti'ying he Business Objects tep G' &dentifying -se ase %ependencies.

ome use cases may be dependent on other use cases, with one

use case lea!ing the system in a state that is a precondition for

another use case.

$e use a diagram called the *se Case ependency iagram

to model dependencies.




Object Modeling


inding And #denti'ying he Business Objects tep G' &dentifying -se ase %ependencies.

The use case dependency diagram pro!ides the following

benefits'

• graphical depiction of the system"s e!ents and their states

enhances the understanding of system functionality.

• &t helps to identify missing use cases. use case with a

precondition that is not satisfied by the execution of any other use

case may indicate a missing use case.

• 5elps facilitate project management by depicting which use casesare more critical (ha!e the most dependencies) and thus need to

ha!e a higher priority.

M b S i S t




Object Modeling

Create New

Seasonal Promotion

Send Club

Promotion

Request Promotion

Rpts.

Create New

Monthly Promotion

Submit Promotion

rder

Send New

Subscription !!er

Send Subscription

Renewal !!er

Submit New

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Request

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Object Modeling


inding And #denti'ying he Business Objects tep H' %ocumenting the -se ase lternate ourse of +!ents

use case has one normal e!ent course that was pre!iously

defined, and possibly many alternate courses.

• lternate courses are de!iations or branches, from the normal

e!ent course.

• lternate courses are documented in a separate use case course.

*"E CA"E




Object ModelingAuthor34452 Bentley ate34 67$7:$89

*"E CA"E /AME3 ubmit 8romotion #rder

AC)O%3 lub /ember

E"C%#&)#O/3 %escribes the process when a club member submits a club promotion order to either

indicate the products they are interested in ordering or declining to order during

this promotion.

/O%MA5

CO*%"E3

1. This use case is initiated when the club member submits the promotion order to

be processed.

2. The club member"s personal information such as address is !alidated against

what is currently recorded in member ser!ices.


G. The club member"s credit status is chec;ed with (ccounts 0ecei!able to ma;e

sure no payments are outstanding.


I. 3or each product being ordered, chec; the a!ailability in in!entory and record

the ordered product information which include )quantify being ordered* and

gi!e each ordered product a status of )open*.

J. reate a 8ic;ing Tic;et for the promotion order containing all ordered


K. 0oute the 8ic;ing Tic;et to the $arehouse.

A5)E%/A)ECO*%"E3

2. &f the club member has indicated an address or telephone number change onthe promotion order, update the club member"s record with the new

information.

F. &f the club member is not ordering product at this time, modify the promotion

order"s status to be )closed* and modify the selection of the month ordered

product"s record to ha!e a status of )rejected*, then cancel the transaction.

G. &f (ccounts 0ecei!able returns a credit status that the customer is in arrears,

in!o;e abstract use case Send Order Rejection Notice. /odify the promotion

order"s status to be )on hold pending payment*.

Ha. &f the product number is not !alid, create an #rder +rror 0eport containing the

club member"s information, the promotion order information and the product

number in error. +ach completed report will be routed to a /ember er!ices

cler; for resolution.

Hb. &f the club member is not ordering the selection of the month, modify theordered product"s record to ha!e a status of )rejected*.

I. &f the product being ordered is not a!ailable, record the ordered product

information which include )quantify being ordered* and gi!e a status of

)bac;ordered*.

J. &f there are no ordered product records with a status of )open*, cancel the

transaction.


&O")-CO/#)#O/3 8romotion order has been recorded and the 8ic;ing Tic;et has been routed to the

$arehouse.

A""*M&)#O/"3




Object Modeling


inding And #denti'ying he Business Objects tep I' 3inding The 8otential #bjects.

This step is accomplished by re!iewing each use case to find

nouns that correspond to business entities or e!ents.

tep J' electing The 8roposed #bjects.

ot all the of the nouns represent good business objects.

0emo!e the nouns that represent'

• ynonyms

• ouns outside the scope of the system• ouns that are roles without unique beha!ior or are external roles

• -nclear nouns that need focus

• ouns that are really actions or attributes

j i




Object Modeling*"E CA"E

Author34452 Bentley ate34467$7;$894

*"E CA"E /AME3 ubmit &romotion Order

AC)O%3 Club Member

E"C%#&)#O/3 %escribes the process when a club member submits a promotion order to either

indicate the products they are interested in ordering or declining to order during

this promotion.

/O%MA5CO*%"E3

1. This use case is initiated when the club member submits the promotion order to be processed.

2. The club member"s personal in'ormation such as address is !alidated against

what is currently recorded in member services.


G. The club member"s credit status is chec;ed with Accounts %eceivable to

ma;e sure no payments are outstanding.


I. 3or each product being ordered, chec; the availability in inventory and record

the ordered product in'ormation which include )1uanti'y being ordered*,

and gi!e each ordered product a status of )open*.

J. reate a &ic,ing )ic,et for the promotion order containing all ordered


K. 0oute the 8ic;ing Tic;et to the +arehouse.

A5)E%/A)E

CO*%"E3

2. &f the club member has indicated an address or telephone number change on

the promotion order, update the club member<s record with the new

information.

F. &f the club member is not ordering product at this time, modify the promotion

order"s status to be )closed* and modify the selection o' the month ordered

product"s record to ha!e a status of )rejected*, then cancel the transaction.

G. &f Accounts %eceivable returns a credit status that the club member is in

arrears, in!o;e abstract use case Send Order Rejection Notice. /odify the

promotion order<s status to be )on hold pending payment*.

Ha. &f the product number is not !alid, create an Order Error %eport containing

the club member"s information, the promotion order information and the

product number in error. +ach completed report will be routed to a Member

"ervices cler, for resolution.

Hb. &f the club member is not ordering the selection of the month, modify theordered product"s record to ha!e a status of )rejected*.

I. &f the product being ordered is not a!ailable, record the ordered product

information which include )quantify being ordered* and gi!e a status of

)bac;ordered*.

J. &f there are no ordered product records with a status of )open*, cancel the

transaction.


&O")-CO/#)#O/3 8romotion order h as been recorded and the 8ic;ing Tic;et has been routed to the

$arehouse.

A""*M&)#O/"3

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Object Modeling

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Accounts %eceivable /ot relevant 'or current project

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Member "ervices Cler /ot relevant 'or current project

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Object Modeling

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Object Modeling


Organi!ing he Objects and #denti'ying heir

%elationships #nce the business objects of the system ha!e been identified, it is

time to organi=e those objects and document any major conceptual

relationships between the objects.

n Object Association Model is used to graphically depict the

objects and their relationships.

This diagram will also include multiplicity,

generali=ation>speciali=ation relationships and aggregation

relationships.

Obj tM dli




Object Modeling



%elationships tep 1' &dentifying ssociations and /ultiplicity

&n this step we need to identify relationships or associationsthat exists between objects>classes.

• 0ecall that a relationship between two objects>classes is what one

object>class needs to ;now* about the other.

• #nce the relationship ha!e been identified, the multiplicity that

go!erns the relationship must be defined.

Obj tM dli




Object Modeling



%elationships tep 2' &dentifying :enerali=ation>peciali=ation 0elationships

:enerali=ation>peciali=ation relationships may be disco!ered by loo;ing at the object model association diagram.

• %o any associations exist between two objects that ha!e a oneto

one multiplicity?

• an you say the sentence object @ is a object 7* and it be true?

• %o two or more objects ha!e common attributes and beha!iors?

$hy do we want generali=ation>speciali=ation relationships?

• &t allows us to ta;e ad!antage of inheritance which facilitates the

reuse of objects and programming code.

Obj tM dlig




Object Modeling



%elationships tep F' &dentifying ggregation 0elationships

&n this step we must determine if any aggregation orcomposition relationships exist.

ggregation relationships are asymmetric, in that object is

part of #bject but, object is not part of object .

ggregation relationships do not imply inheritance, in that

object does not inherit beha!ior or attributes from object . ggregation relationships propagate beha!ior in that beha!ior

applied to the whole is automatically applied to the parts.

Obj tM dlig




Object Modeling



%elationships tep G' 8reparing The #bject ssociation /odel

&n this step construct the object association model diagramwhich depicts how the objects are related to each other and

what type the relationships are.

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Summary

Introduction An Introduction to Object Modeling System Concepts for Object Modeling


02 object modeling technique

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