Sommerville Chapter 7 Fowler Chapters 1, 3, 5, and 6 ... · Conceptual Modeling and Class Diagrams...

Conceptual Modeling and

Class Diagrams

Sommerville Chapter 7

Fowler Chapters 1, 3, 5, and 6

Announcements

HW2 handout now available on the

webpage.

Interpration of throttle position and its

relation to acceleration is different in HW2

Next tutorial in Week 4 on class diagrams

and sequence diagrams

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Objective for Today

To introduce conceptual modeling The goal of conceptual modeling

To review the OO solutionTo introduce and discuss the object model

(conceptual) Syntax and semantics

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Common Problems

The requirements are

wrong Incomplete, inconsistent,

or ambiguous The developer and the

customer did not

interpret the

requirements the same

way

Requirements drift The requirements tend to

change throughout the

project Late design changes

Continual change The functionality of the

system continually

changes Many changes come late

in the project Many changes during

maintenance

Breakdown of system

structure The system finally

becomes unusable

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Solutions

Rigorous requirements and planning stage Make sure all stakeholders understand and

agree on the requirementsStructure the system design to

accommodate change Isolate parts that are likely to change Modularize so changes are contained Attempt to not compromise system structure

during change


The OO Solution

The problem domain is relatively constant Auto pilot Get a plane from point A to point B using the available

control surfaces


The OO Solution

The problem domain is relatively constant Auto pilot Get a plane from point A to point B using the available control

surfacesThe functionality and data representation is what is likely to

change Auto pilot The hardware interfaces are different between different

models The operational modes vary between models and evolve over

time


The OO Solution

The problem domain is relatively constant Auto pilot Get a plane from point A to point B using the available control

surfacesThe functionality and data representation is what is likely to

change Auto pilot The hardware interfaces are different between different

models The operational modes vary between models and evolve over

time


Structure the system based on the structure of the problem

domain, NOT based on the structure of the solution

What is OO

A way of thinking about a problem (software)

based on abstractions of concepts that exist in

the real worldOO is not constrained by implementation

language (C, Pascal, FORTRAN , etc. will

work)


What is not OO

Using an “object oriented” language (C++, Eiffel,

Smalltalk) You can easily misuse the OO support in these

languages

Using an “OO notation” for design Misuse the notation for a non-OO design

Calling what you do OO Management and customers like OO, therefore, that is

what we are doing


OO is not the answer to all your problems

Several Complementary

Models

Structural Models Describes the structure of the objects in a system Structure of individual objects (attributes and

operations) Relationships between the objects (inheritance,

sharing, and associations) Clustering of objects in logical packages and on the

actual hardware

Dynamic models (behavioral models) The aspects related to sequencing of operations Changes to attributes and sequences of changes The control aspects of the system


Conceptual ModelingA Short Discussion

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Conceptual Modeling

Early modeling to understand the problem

Conducted in cooperation with the

customer Domain experts Domain engineers

No real problem analysis if the customer is

not involvedPower of OO It is simple and people can quickly participate

effectively Or so they say…


The OO Solution


The OO model closely resembles the

problem domain Base your model on the objects in the problem

domainIteratively refine the high-level model until

you have an implementation Attempt to avoid big conceptual jumps during

the development process

The OO Solution (Cont.)

Organize the model as a collection of objects Concrete concepts in the physical world A drivers license, a credit card, an aircraft, etc.

Logical concepts A scheduling policy in an OS, ATC conflict resolution rules,

etc.

Encapsulate all information within the objects Data representation Characteristics of the object - the object attributes

Functionality (behavior) What the object can do - what operations can the object

perform


Fall 2013CSci 5801 - Dr. Mats Heimdahl16

Ajitha Rajan

123 4567 887766 998

Ajitha Rajan

Drivers License

A-123456

Objects

Characteristics of Objects

Identity Discrete and distinguishable entities

Classification Abstract entities with the same structure

(attributes) and behaviour (operations) into

classesPolymorphism The same operation may behave different on

different classesInheritance Sharing of attributes and operations based on a

hierarchical relationship


The Class Diagrams

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Objects

Something that makes sense in the

application context (application domain) Ajitha Rajan Joe’s Homework Assignment 1 Ajitha’s drivers license

All objects have identity and are

distinguishableNOT objects Person Drivers license

Classes

Describes a group of objects with similar

properties (attributes), common behavior

(operations), common relationships to other

classes, and common semantics Person Ajitha Rajan Joe Smith Allan Clark

Card Credit card Drivers license Teller card


Attributes and Operations


Attributes

name

age

height

weight

Operations

move

change-job

Attributes

height

width

id-number

Operations

issue

change

Person objects

Card objects

Person class

Card class

abstracts to

Ajitha Rajan

Drivers License

A-123456Ajitha Rajan

123 4567 887766 998

Lisa Heimdahl

32

Person

Mats Heimdahl

33

Person

Class Diagrams

Fall 2013 CSci 5801 - Dr. Mats Heimdahl 22

Class with attributesObjects with values

Objects have an identity

Do not explicitly list

object identifiers

SSN OK!

Class diagram Instance diagram

person ID: integer

name: String

age: integer

Person

name: String

age: integer

Person

Class Diagrams


Class with attributesObjects with values

Objects have an identity

Class diagram

person ID: integer

name: String

age: integer

Person

name: String

age: integer

Person

Instance diagram

-name = Lisa Heimdahl

-age = 32

Person-1 : Person

-name = Mats Heimdahl

-age = 33

Person-2 : Person


Operations and Methods

Transformation that can be

applied to or performed by an

object

May have arguments

issue()

revoke()

height: integer

width: integer

thickness: integer

id-number: integer

Card

rotate(angle: integer)

move(x: integer, y: integer)

height: integer

width: integer

Shape


Object Notation - Summary

operation-1(argument-list-1) : result-type-1



attribute-1 : data-type-1 = default-value-1



Class name


Associations

Conceptual connection between classes A credit card is issued-by a bank A person works-for a company

Class diagrams

Instance diagram

Credit Card BankIssued-by

Person CompanyWorks-for

-name = Mats Heimdahl

-age = 33

Person-2 : Person U of M : Company

1 1

Works-for


Associations are Bi-

directional

There is no direction implied in an

association

Country

name

Drivers-license

lic.-number: integer

Person

name

City

nameHas-capital

Is-issued


Associations Have Direction

Unified adds a direction indicator

Country

name

Drivers-license

lic.-number: integer

Person

name

City

nameHas-capital

Is-issued


Multiplicity

One object can be related to many objects

through the same association

One person holds

one credit card

One person can hold

zero or more credit

cards

(* stands for many)

name: String

Person

card-number: integer

Credit-cardHolds

name: String

Person


Credit-cardHolds 0..*


Multiplicity

One object can be related to many objects

through the same association

One person holds

one credit card

One person can hold

zero or more credit

cards

(* stands for many)

name: String

Person


Credit-cardHolds

name: String

Person




One person can hold zero or more credit cards (0..*)

Each card has zero or one holder (0..1)

Multiplicity (Cont.)

Mats Heimdahl

33

Person 123 456 789

Credit-Card

111 222 333

Credit-Card

Holds

Holds

name: String

Person


Credit-cardHolds 0..*0..1

111 222 333

Credit-Card

Lisa Heimdahl

32

Person



Each card has zero or one holder (0..1)


Mats Heimdahl

33

Person 123 456 789

Credit-Card

111 222 333

Credit-Card

Holds

Holds

name: String

Person


Credit-cardHolds 0..*0..1

111 222 333

Credit-Card

Lisa Heimdahl

32

Person




Each card has one holder (no indication or 1)

Each card has one or more authorized users (1..*)

One person can be authorized to use zero or more cards

Explicit enumeration is also

possible (2, 3, 2..5, etc.)

Lisa Heimdahl

32

Person

Mats Heimdahl

33

Person 123 456 789

Credit-Card

111 222 333

Credit-Card

111 222 333

Credit-Card

Holds

Holds

Autorized

Holds

Autorized

Autorized

Autorized

name: String

Person



Autorized

1

1..* 0..*


How represent salary and

job title?

Use a link attribute!

Link Attributes

Associations can have properties the same way objects have

properties

name: String

age: integer

SSN: integer

address: String

Person

name: String

address: String

CompanyWorks-for 0..*

name: String

age: integer

SSN: integer

address: String

Person

name: String

address: String


salary: integer

job-title: String

Folding Link Attributes into

Class


Why not this?

Salary and job title are

properties of the job

not the person

name: String

age: integer

SSN: integer

address: String

salary: integer

job-title: String

Person

name: String

address: String


name: String

age: integer

SSN: integer

address: String

Person

name: String

address: String


salary: integer

job-title: String

0..*In this case, a link attribute is the only solution

Ordering

The objects on the “many” side of an association does not

have order.Imply ordering with the ordered attribute

WindowScreenVisible 0..*

{ordered}WindowScreen

Visible 0..*


General Constraints

Express constraints in plain EnglishDraw a dotted line if feasibleDo not clutter the diagram with constraint arrows!


Attribute Constraints

Constraints on the attributes Card number must be a 12 digit number Worker’s salary is always less than the salary of

the boss

Credit-card


{card-number is 12 digits}

Employee

name

salary

address

boss

workerManages

{worker.salary < boss.salary}

0..*

0..1

39

Navigability

Indicates you can get information about

objects in only one direction Pointer from one object to the next Object defined as a member in the

implementation

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Role Names

Attach names to the ends of an association

to clarify its meaning

name: String

age: integer

SSN: integer

address: String

Person

name: String

address: String

CompanyWorks-for 0..* 0..*

salary: integer

job-title: String

employeremployeeboss

workerManages

0..*

0..1

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Higher order associations

Ternary association Project, language, person

Language

Person

Project1..*

1..*

1..*

Mats Heimdahl

33

Person

Compiler

Project

C++

Language

TicTacToe

Project

LISP

Language

42

Aggregation symbol

Aggregation

A special association, the is-part-of

association A sentence is part of a paragraph (a paragraph

consists of sentences) A paragraph is part of a document (a document

consists of paragraphs)

Document Paragraph Sentence0..* 0..*

43

Aggregation (Cont.)

Often used in parts explosion

Car

Wheel Body Gearbox Engine

Door Hood Trunk Piston Valve Crankshaft

0..*1..* 1..*

4

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Generalization and Inheritance

The is-a association Cards have many

properties in common Generalize the common

properties to a separate

class, the base-card Let all cards inherit from

this class, all cards is-a

base-card (plus possibly

something more)

issue()

revoke()

height: integer

width: integer

thickness: integer

id-number: integer

Card

expire()

class: vehicle

issued: date

expires: date

Drivers License

expire()

issued: date

expires: date

ID Card

validate()

credit-limit: integer

issued: date

Credit Card

45

Example

name

City

name

Airline

name

license

Pilot

name

Passenger

heat()

clean()

name

Airport

cancel()

delay()

date

fl ight #

Flight

heat()

refuel()

clean()

model

serial #

hours flown

Plane

reserve()

location

Seat

Based-In 0..*

Departs

Works-for

Arrives Used-For

Certified-On

Owns

Located-In

0..*

Offers

Pilots

Confirmed-for

0..*

0..*

0..*

1..*

0..*

0..*0..*

0..*

30..*


Aggregation Versus

AssociationCan you use the phrase is-part-of or is-made-ofAre operations automatically applied to the parts (for

example, move) - aggregationNot clear what it should be……

Company DepartmentDivision

Person

0..*

Works-for

0..* 0..*


Aggregation Versus

InheritanceDo not confuse the is-a

relation (inheritance) with

the is-part-of relation

(aggregation)Use inheritance for

special cases of a

general conceptUse aggregation for parts

explosion

Car

Wheel

Body

Gearbox

Engine

4

Station

WagonCompact 4 by 4

Transfer

Case

Object Modeling Summary

Classes● Name● Attributes● Operations

Associations

Roles Link attributes

Aggregation

Inheritance

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In Class Examples

Draw a class diagram for a

book chapter with the

following structure. A chapter

comprises several sections,

each of which comprises

several paragraphs and/or

figures. A paragraph

comprises several

sentences, each of which

comprises several words. Note 1: You may ignore

punctuation and you need

not pursue the structure of

a figure any further. Note 2: “Several” in the text

above refers to “one or

more”.

Draw a class diagram (using

inheritance) that captures

two categories of a

company’s customers:

external customers, which

are other companies buying

goods from this company,

and internal customer, which

are all the divisions of this

company.

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Suggested Solution

Chapter Section Section Component

ParagraphSentenceWord Picture

1 1..* 1 1..*

11..*11..*

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Another Suggested Solution

Corporate Division Customer

Internal Customer External Customers

Object Modeling Approach

Sommerville Chapter 7

Fowler Chapters 1, 3, 5, and 6

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Objective

To introduce one way of getting a model

startedIntroduce a way of starting to find

responsibilities, collaborators, and

relationships


Object Modeling Approach

Start with a problem statement High-level requirements

Define object model Identify objects and classes Prepare data dictionary Identify associations and aggregations Identify attributes of objects and links Organize and simplify using inheritance Iterate and refine the model Group classes into modules

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The Home Heating System


90

80

70

60

50

On

Off

Controller

Fuel Valve

Burner

Water Pump

Hot Water

Fuel

Temp Sensor

Water Valve

Control Panel

Home

Home Heating Requirements


The software shall control the heat in each

room The room shall be heated when the

temperature is 2F below desired temp The room shall no longer be heated when

the temperature is 2F above desired temp The flow of heat to each room shall be

individually controlled by opening and

closing its water valve The valve shall be open when the room

needs heat and closed otherwise The user shall set the desired temperature

on the thermostat The operator shall be able to turn the

heating system on and off The furnace must not run when the system

is off

When the furnace is not running and a room needs

heat, the software shall turn the furnace on To turn the furnace on the software shall follow

these steps open the fuel valve turn the burner on

The software shall turn the furnace off when heat

is no longer needed in any room To turn the furnace off the software shall follow

these steps close fuel valve turn burner off

The purpose of the software for the Home Heating System is to control the heating

system that heats the rooms of a house. The software shall maintain the temperature of

each room within a specified range by controlling the heat flow to individual rooms.

57

Requirements

Statements

Extract

Nouns

Tentative

Object Classes

Eliminate

Spurious Classes

Object

Classes

Candidate Classes

Controller

Fuel Valve

Burner

Water Pump

Hot Water

Fuel Temp Sensor

Water Valve

software

Home Heating System

heating systemroom

house

temperature

heatdesired temp

operator

thermostatfurnace

on-off switch Control Panel

Home

range

Identify Object Classes

Eliminate Bad Classes

Redundant classes Classes that represent

the same thing with

different words

Irrelevant classes Classes we simply do

not care about

Vague classes Classes with ill defined

boundaries

Attributes Things that describe

individual objects

Operations Sequences of actions are

often mistaken for classes

Roles The name of a class should

reflect what it is, not the role it

plays

Implementation details Save that for implementation

58

Controller

Fuel Valve Burner

Water Pump

Hot Water

Fuel

Temp Sensor Water Valve

software

Home Heating System

heating system

room

house

temperature

heat desired temp

operatorthermostat

furnace

Redundant Irrelevant Vague Attributes

Operations ImplementationRoles

None NoneNone

heat flow

on-off switch Control Panel

homeuser

range

Eliminate Classes

60

Controller

Fuel Valve

Burner

Water Pump

Temp Sensor

Water Valve

Home Heating System

Room

Operator

Thermostat Furnace

on-off switch

Control Panel

Classes After Elimination

Prepare Data Dictionary

Water Tank The storage tank containing the water that

circulates in the system.Pump-1 The pump pumping water from the Water Tank

to the radiators in the roomsEtc.Etc.

61


Possible Associations

A room consists of a thermometer and a radiator A radiator consists of a valve and a radiator element The home heating system consists of a furnace, rooms, a water

pump, a control panel, and a controller The furnace consists of a fuel pump and a burner The control panel consists of an on-off switch and a thermostat The controller controls the fuel pump The controller controls the burner The controller controls the water pump The controller monitors the temperature in each room The controller opens and closes the valves in the rooms The operator sets the desired temperature The operator turns the system on and off The controller gets notified of the new desired temperature

Class Diagram

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Home Heating

System

Control Panel

On-Off Switch Thermostat

Room

Operator

Water Valve Temp Sensor

Furnace

Burner

Water Pump

Fuel Valve

Controller

Pushes Adjusts

Notifies

Monitor

Actuates

Ignites

Opens/Closes

Runs

1..*

Class Diagram (Better?)

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Control Panel


Room

Operator


Furnace

Burner

Water Pump

Fuel Valve

Controller

Pushes Adjusts

No

tifies

M

on

itor

A

ctu

ate

s

Ignites

Opens/Closes

Runs

65

Class Diagram - Modified

Home Heating

System

Control Panel


Room

Operator


Furnace

Burner

Water Pump

Fuel Valve

Controller

Pushes Adjusts

Notifies

Monitor

Heats

Ignites

Opens/Closes

Runs

1..*

1..*

1..*


Class Diagram—Alternate

Fuel Valve Burner

Water Pump

Thermostat

Operator

Room


Furnace

Power Switch

Control Panel

11

11

1 111

11

11

1

*

Notify

*

1

Request Heat

1

1

Start

1

1

Adjust1

1 Push

67

Temp Sensor

temperature

Thermostat

desired-temp

On-Off switch

setting

Attributes

68

Final Class Diagram

Home Heating

System

Control Panel

setting

On-Off Switch

desired-temp

Thermostat

Room

Operator

Water Valve

temperature

Temp Sensor

Furnace

Burner

Water Pump

Fuel Valve

Controller

Pushes Adjusts

Notifies

Monitor

Heats

Ignites

Opens/Closes

Runs

1..*

1..*

1..*


Final Alternative

Fuel Valve Burner

Water Pump

-Desired Temp

Thermostat

Operator

Room

Water Valve

-Temperature

Temp Sensor

Furnace

-setting

Power Switch

Control Panel

11

11

1 111

11

11

1

*

Notify

*

1

Request Heat

1

1

Start

1

1

Adjust1

1 Push

Iterate

Iterate the Model

Keep on doing this

until you, your

customer, and your

engineers are happy

with the model

Different Types of Interaction

Diagrams

An Interaction Diagram typically captures a

use-case A sequence of user interactions

Sequence diagrams Highlight the sequencing of of the interactions

between objectsCollaboration diagrams Highlight the structure of the components

(objects) involved in the interaction



Home Heating Use-Case

Use case: Power Up

Actors: Home Owner (initiator)

Type: Primary and essential

Description: The Home Owner turns the power on. Each room

is temperature checked. If a room is below the

the desired temperature the valve for the room is

opened, the water pump started, the fuel valve

opened, and the burner ignited.

If the temperature in all rooms is above the desired

temperature, no actions are taken.

Cross Ref.: Requirements XX, YY, and ZZ

Use-Cases: None

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Class Diagram—v1

Control Panel

setting

On-Off Switch

desired-temp

Thermostat

Room

Operator

Water Valve

temperature

Temp Sensor

Furnace

Burner

Water Pump

Fuel Valve

Controller

Pushes Adjusts

No

tifies

M

on

itor

H

ea

ts

Ignites

Opens/Closes

Runs

1..*

1..*


Sequence Diagrams (for cd—

v1)

Sequence Diagrams (old)

(for cd—v1)


We Have Learned

An object is an entity in the problem domainA class is an abstraction of a collection of objectsObjects (classes) have attributes and operations Objects (classes) are related to each other trough associations

Regular association Aggregation Inheritance

Associations have multiplicity May have link attributes

Role names may be used to clarify the model


We Have Learned

How to approach an OO modeling effort Identify objects (nouns) Identify associations (typically verbs) Identify attributes and operations

The model will need a lot of iteration In conjunction with other models we have not

yet talked about We will the next few lectures


Sommerville Chapter 7 Fowler Chapters 1, 3, 5, and 6 ... · Conceptual Modeling and Class Diagrams...

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Transcript of Sommerville Chapter 7 Fowler Chapters 1, 3, 5, and 6 ... · Conceptual Modeling and Class Diagrams...