Events and Signals

OOAD: Object Oriented Modeling

Handling Complexity 

• Complexity of systems can be in structure or in behavior 
• Model complex systems that can deal with their complexity 
• There are two ways to model software systems. They are: 

Algorithmic  

Here, the primary focus is on behavioral complexity. It consists of Procedures and functions 

Object-oriented

In this, the primary focus is on structure and then the behavior. Object-oriented consists of 

Classes and objects (structures) 

Functions or methods (behavior)  

• In Object-oriented programming, programs are organized as cooperative collections of objects 
• An Object-oriented program is structured as a community of interacting agents, called objects 
• Each object has a role to play 
• Each object provides a service or performs an action, that is used by the other objects 
• A class is a representation for a set of objects that are data abstractions with an interface of named operations and hidden local state 
• All objects are instances of a class 
• The methods invoked by an object in response to a message is determined by the class of the receiver
• All objects of a given class use the same method in response to similar messages
• Modern enterprise software development heavily adopts the object-oriented approach 
• Most of the programming languages, operating systems and tools view the systems in an object-oriented fashion In this approach the primary building block is object or class 

Example: 

A 3-tier online shopping system that has a user interface, business services and database layers 

• We will find objects like buttons, menus and dialog boxes in user interface 
• The middle layer, has objects like transactions, business rules and views of problem entities that include customers, products and orders 
• There are database objects like tables that include customers, products and orders  

Modeling at Glance