 Today, we are going to discuss the topic object model. At the end of the session, a student will be able to analyze a real-world problem and create an object model for this particular problem. When we consider object-oriented development, this is not constrained to build up a new designing technique. However, it is a new way of thinking which is based on abstractions. These processes are independent of any programming language and you could design a particular software before its development in any programming language using such techniques. It stresses on the application of domain concepts because we are considering things of the real world. And it uses modeling along with graphical notations to make things more understandable for a particular user. The two methodologies that we use when considering object-designing and object-modeling are first, the object-modeling technique or OMT which is given by James Ranberg. It consists of steps dealing with the analysis and creation of an object model, a dynamic model and a functional model which forms a tripod for your particular design. Based upon this particular requirement of your tripod, we then go in to develop a system design to implement our particular tripod. And then we go for object design to then formulate our particular problem in the form of a design. There is large amount of paperwork involved here. There is large amount of creativeness involved here. The second technique is a technique designed by Gradibuch which is unified modeling language. The UML which has generated through n number of generation phases and got its standardization today to be developed at a very high level. Wherein sometimes a design which is done in UML can be directly given and the code can be developed in a language like Java or VC++ as required. It does an analysis and the drawing of the nine diagrams which are involved, which gives details about all the designing aspects that are required for a particular software design. The object model captures the static structure showing the objects in a system, the relationship between the objects in a particular system, the operations that characterize each class of the particular objects. And we represent these models in the form of two diagrams. One diagram is a class diagram and one diagram is an instance diagram. The class diagram gives all the classes and its relationships between the classes being expressed in that particular diagram. And an instance diagram gives the objects which are present at a particular instance of time. So objects and classes are the first concept to be explained to you. Objects are entities of interest. They promote understanding of the real world. They provide practical basis for implementation. They express a particular concept. They express abstraction or the thing with the crisp boundaries. So we are thinking of all the particular aspects of our particular real world problem in the form of objects. These are entities to be taken into consideration. Classes is a group of objects which have similar attributes or properties. They have similar operations or behavior. They have common relationships to other objects in the class and they have common semantics. We represent classes and objects in this particular form. Every class will have a class name. It will have its attributes which describe the particular class and it has the operations which can be performed on a particular class. In an instance diagram we have an object which has an object name. We have its attributes attached to it and we have operations that can be performed on that particular attribute. Classes are seen in the class diagram and objects are seen in the instance diagram. The next concept is attributes and operations. Attributes are data values held by objects in the class. One attribute for each object instance is considered. Attribute name is unique within a class. Attribute is a pure data value and not an object. Attribute do not have identity. Whereas operations are functions or transformations performed to a particular class. They may be applied specifically to the class and objects of the class share the same operations. Each operation has a target object as implicit argument. The behavior of operations depends on the class of target and the method of implementation of operation for a particular class. Links which are represented by a directed arrow. They establish relationship among objects and classes. Links are shown in the instance diagram and associations are shown in the class diagram. Link is physical or conceptual collection between object instances. It is an instance of an association. Link attributes is a property of the link in a particular association. When we go for associations which we represent as a bidirectional arrow. We describe the group of links with the common structure and semantics. The associations are inherently bidirectional and all connections among the classes are modeled as associations. The role is one end of a particular association. Aggregation represented as a filled diamond is an aggregation which is a part whole of a part of relation. Object representing components with objects represent the entire assembly. So aggregation involves a part whole of a particular relation. As an example, let us take the listing of the objects in a college automation system. Here we see the objects which are university, college, department, student and faculty which are involved. We have roles expressed with numbers. One, we have aggregations expressed as diamonds. We have associations expressed as arrows. If we do not put a particular arrow on the association, it still means that association is bidirectional. As an assignment, let us think of drawing a class diagram and instance diagram for a hospital management system. Let us think for a while of all that is involved in this particular assignment. So the objects might be a ward, a patient, a doctor, a nurse, a ward boy, the machinery, the apparatus, the rooms where the patient is admitted, the cots, the bed, all these are then related by particular relationships between them. So right from a patient enters the particular hospital till a billing is handed into his hand has to be designed and taken into consideration because we are developing a total real world system which is a hospital management system. For our references we have used. Thank you.