1. Object Oriented Systems

• Object Oriented Analysis and Design is a specialised method

It is often viewed as a strategic move to develop an Object Oriented information architecture

Its popularity came about as a result of the failings and problems associated with relying on traditional software development methods

2. Information Architectures

The problems associated with building an information architecture based upon procedural software systems are many

The software maintenance issues with traditional environments are a real problem

In reality the re-usability levels were never very high

3. Problems with Software Architectures

Software development is still very expensive

Organisations do make great use of existing code - code reuse?

• Why do you think this is?

4. O.O. Development

O.O. development proposed a number of advantages

It combines processes, data and flows into one modeling paradigm

This allows objects to be modeled as independent entities that can be flexibly combined into cooperating systems

Easy conversion from analysis to design models through the use of similar terms

5.

Supporting multimedia information and not only record structures

• video

• sound

• graphics

• as well as text

Requirements in organisations have moved on .

6. An Object Showing Encapsulation PROPERTIES Project-No: P56; Manager: ref PERSONS; Start-Date: 10-1-2000; Budget: 180000 People-Assigned: PERSONS; Tasks: ref PROJECT-TASKS; METHODS Add-Person(); Delete-Person(); Create-Task(); Change-Budget(); Fig:11.2 in ref 7. O.O. Method

O.O. architectures are a bottom-up approach to developing information architectures - at least on a software and data level

In the O.O. paradigm it is not necessary to think of developing one large system

Objects act as independent entities with their own local goals

Objects can then exchange messages between themselves to achieve a global goal of the large system

8. Object Architectures Project-No: P56; Manager: ref PERSONS; Start-Date: 10-1-2000; Budget: 180000 People-Assigned: PERSONS; Tasks: ref PROJECT-TASKS; Add-Person(); Delete-Person(); Create-Task(); Change-Budget(); Persons Project SURNAME: Gilligan; Date of Birth: 14-Jan-65; Date-Joined: 7-April-93; Position: Manager; Pay-Rate:6/3; Change-Position(); Change-Payrate(); Tasks Task-No:4; Date:1-6-2000; Description:Install SW Progress: ref DOCUMENT Update-program(); 9. Encapsulation & Autonomy

Encapsulation - of data and methods

Eliminates the need to store data and processes separately

This should make changes easier to make

Facilitates the idea of cooperating independent systems

10. O.O. Implementations

Growing number of products-

• languages such as C++, Java

• database systems

It is one common paradigm for architecture, analysis, design and implementation

Not the case in other approaches eg. Structured Development

11. ReUse

As objects are autonomous they should be easily plugged into systems - reuse

In traditional systems the system is seen as a set of functions, data and processes

12. Inheritance

Inheritance is an important concept in the Object Oriented paradigm

Classes can be arranged hierarchically with the most general features in the top level class or superclass and the more specific features in the sub classes

The subclasses inherit all the instance variables and methods of the superclasses

13. Inheritance Offers Producer: Time-Available: Add-Offer(); Delete-Offer(); OFFERS ITEM-OFFERS Quantity: Price/Item: Compute Value(); VOLUME-OFFERS Weight; Price/KG: Compute Value(); Bank Example 14.

The important thing about all this is that firstly the software becomes more modular

and secondly, the superclasses are being reused instead of redefining them all in the subclasses.

15. Use Cases

Use cases are scripts that describe instances of how a system is used

The main actors and roles are identified

The way they interact with the system is described

16. Use Case - Make a sale

• A buyer

• • Initiates a trade by creating a trader and requesting a stated amount of a selected product

• • the trader finds product-offers that satisfy the request through the product, by obtaining offer volumes and prices, & displays to buyer

• • the trader initiates the sale through products.The sale is verified to the buyer, & producer advised to arrange transport and invoice

• Seller arranges delivery with transport company by:

• • creating a delivery docket

• • callinga number of companies for quotes

• • agreeing on time and charge

• • recording agreement on delivery docket

Used to identify Objects (properties and methods) 17. O.O. Through Java

Java is an object oriented language and is a good language to demonstrate object oriented principles

This is because it was developed using a clean slate approach (Naughton & Schildt, 1997).

In other words, Java was not designed to be source compatible with any other language

18.

The object model in Java is simple and easy to extend, while simple types, such as integers, are kept as high performance non-objects

Java supports the following object oriented constructs.

• • Classes and objects

19.

Classes act as templates for the creation of objects and hence the class construct is reused

The listing below creates a class calledContainerwith three data items and a method to compute the volume of the container

Parameters are passed from theContainerDemclass when objects are created and the data for the object is initialised by theContainerconstructor

Two objects are created : container1 and container2inContainerDem . The volume method is then called for each object, and the results returned and displayed in the DOS window.

20.

// Java program to demonstrate the use of classes and objects

// Container uses a constructor to// initialize the dimensions of a container.

class Container {double width;double length;double depth;// The constructor for container.

Container(double w, double l, double d) {

width = w;

height = l;

depth = d;

}

// The volume of the container is returned

double volume() {

return width * length * depth;

}

}

21.

class ContainerDem {

public static void main(String args[]) {

// declare and initialize container objects

Container container1 = new Container(5, 10, 15);

Container container2 = new Container(4, 6, 10);

double vol;

// Use the volume method for the first container

vol = container1.volume();

System.out.println("The volume of container1 is " + vol);

// Use the volume method for the second container

vol = container2.volume();

System.out.println("The volume of container2 is " + vol);

}

}

22. Questions

Explain the main benefits of the O.O. Paradigm

What role does O.O. play in the Information Architecture

Contrast and compare Information Engineering and Object Orientation