Complex objects: It represents the concept and type of the feature support class that defines a set of similar objects. Security attributes of objects and respond to the same message can be combined together to form a class. Related to the properties and methods of the class definition, rather than individually for each object. Variables and the type of the expression helps in compile-time type checking, check the correctness of the program.
Object identity: Object identity is a unique identity of each object objects regardless of its contents; even if all attributes are the same, objects have different OIDs. An object is made of two components i.e. the attributes and the methods. The data with which the characteristics of an object are defined is known as Attributes. The examples of this kind of data include integers, strings, and real numbers and it can also be complex objects reference. The behavior of an object which is formally also known as procedures or functions are termed as Methods. It allows attributes to store a reference to other tuples. The relationships between types of rows and a row that is uniquely identified in a table are defined by using various methods. The actual OID values are not visible to users and cannot be queried.
Types and classes: The object-oriented model has powerful type system and it has primitive types such as integer, string, date and Boolean etc. Structure types are the attributes that can be recorded with a schema. Collection types are the attribute that can be a set, bag, list, and array of other types. Reference types are the attributes that can be a pointer to another type. An object can act as template in the object class. The structure is specified which is made up of the set of attributes of the instances, a set of operations and set of methods through which the operations are implemented.