Informática II Prof. Dr. Gustavo Patiño MJ 16- 18 05-09-2013.

Informática IIProf. Dr. Gustavo PatiñoMJ 16- 1805-09-2013

Informática II. Facultad de Ingeniería. Universidad de Antioquia. 2013-2

A model is a simplification of reality.Main reason for developing models:

Understanding the system being developed.

We build models of complex systems because we can not comprehend such a system in its entirety.


The choice of the model has a significant impact on how the problem is approached and how a solution is devised. A model can be expressed at different

levels of precision. A good model is connected to reality. A single model is not sufficient to represent

most systems.▪ A set of nearly independent models are required.


Modeling is an essential part of all the disciplines in engineering, including software engineering.

The importance of having a “good” model increases with the complexity of the project.


Software engineering is an engineering discipline. A modeling technique suitable for the

programming approach should be used. Since object-oriented approach has

proven to be superior to other approaches, models designed for this approach are widely used in software engineering.


Objects are abstractions of real-world or system entities and manage themselves.

Objects are independent and encapsulate state and representation information.


System functionality is expressed in terms of object services.

Shared data areas are eliminated. Objects communicate by message passing.

Objects may be distributed and may execute sequentially or in parallel.


Easier maintenance. Objects may be understood as stand-

alone entities.Objects are appropriate reusable

components.For some systems, there may be an

obvious mapping from real world entities to system objects.



OOA is concerned with developing an object model of the application domain.

OOD is concerned with developing an object-oriented system model to implement requirements.

OOP is concerned with realising an OOD using an OO programming language such as Java or C++.


Object Orientation Abstraction Encapsulation Modularity Hierarchy


A model that includes most important aspects of a given problem while ignoring less important details.

An example of an item purchasing abstraction.


Counter

Queue Item

Hide implementation from clients Clients depend on interface


The breaking up of something complex into manageable pieces or modules

Canteen System

Queue

Order Placement

Delivery

Billing


Level of abstraction

Increasing abstraction

Decreasing Abstraction

Art

Music Films Sculptures

R&B Rap Sci-Fi Action


ObjectClassAttributesOperation Interface (Polymorphism)ComponentsPackageSubsystemRelationships


Informally, an object represents an entity, either physical, conceptual, or software Physical entity

Conceptual entity

Software entity

truck

Chemical Process

Linked List Data Structure


An object is a concept, abstraction, or thing with sharp boundaries and meaning for an application

An object is something that has State Behavior Identity


The state of an object is one of the possible conditions in which an object may exist

The state of an object normally changes over time

Represented by: Attribute values + Links (relationship instances)

Y.Welikala

Name:

Employee ID:

Date hired:

Status:

Y.Welikala

567138

Oct 18, 2004

Teaching


Behavior determines how an object acts and reacts to requests from other objects

Behavior is represented by the set of messages it can respond to (the operations the object can perform)

Registration System

Assign Y.Welikala

(Returns: confirmation)

CS 201 Course


Each object has a unique identity, even if its state is identical to that of another object

Y. Welikala Teaches OOP

“Y.Welikala” Teaches OOP

“Y.Welikala” Teaches OOP


An object is represented as rectangles with underlined names

: Lecturer

Y.Welikala : Lecturer

Class Name Only

Class and Object Name

Y.Welikala

Object Name Only


Intro to OO 201

Algebra 110

Electricity 100

Algorithms 202

ThermalDynamics 110

Electronics 110

English 101


A class is a description of a group of objects with common properties (attributes), behavior (operations), relationships, and semantics. An object is an instance of a class


A class is an abstraction in that it: Emphasizes relevant characteristics Suppresses other characteristics


Class

CourseProperties

Name

Location

Days offered

Credit hours

Start time

End time

Behavior

Add a student

Delete a student

Get course roster

Determine if it is full


How many class can you see?


A class is an abstract definition of an object It defines the structure and behavior of

each object in the class It serves as a template for creating

objectsObjects may be grouped into classesLecturer

Lecturer Yohan Lecturer Chinthana Lecturer Smith


Class

Attribute

CourseOffering

numberstartTimeendTime

:CourseOfferingNumber=CS201

endTime=1230startTime=1030

Object

Attribute Value

:CourseOfferingNumber=CS202

endTime=1500startTime=1300


CourseOffering

addStudent

deleteStudent

getStartTime

getEndTime

Class

Operation


What are the game’s objects?

What do those objects know how to do?

What properties do they have?


What are the game’s objects? piece, board

Capabilities: What do those objects know how to do? piece:▪ be created▪ fall▪ rotate▪ stop at collision


board:▪ be created▪ remove rows▪ check for end of game

Properties: What attributes and components do they have? piece:▪ orientation▪ Position▪ shape▪ color

board:▪ size▪ rows


Informática II Prof. Dr. Gustavo Patiño MJ 16- 18 05-09-2013.

Documents

interface informtica

object model

system objects

good model

object oriented system

single model

counter queue item slide

system entities