Object Type

Object types are abstractions of the real-world entities
An object type has a name, which serves to identify the object type uniquely within that schema. It has attributes, which model the structure and state of the real world entity. Attributes are built-in types or other user-defined types.
It has methods, which are functions or procedures written in PL/SQL and stored in the database, or written in a language like C and stored externally. Methods implement operations the application can perform on the real world entity.
An object type is a template. A structured data unit that matches the template is called an object. An object type has attributes, which reflect the entity's structure, and methods, which implement the operations on the entity. Attributes are defined using built-in types or other object types. Methods are functions or procedures written in PL/SQL or an external language like C and stored in the database. A typical use for an object type is to impose structure on some part of the data kept in the database. For example, an object type named DataStream could be used by a cartridge to store large amounts of data in a character LOB (a data type for large objects). This object type has attributes such as an identifier, a name, a date, and so on. A method is a procedure or function that is part of the object type definition and that can operate on the object type data attributes. Such methods are called member methods, and they take the keyword MEMBER when you specify them as a component of the object type. The DataStream type definition declares three methods. The first two, DataStreamMin and DataStreamMax, calculate the minimum and maximum values, respectively, in the data stream stored inside the character LOB.
The system implicitly defines a constructor method for each object type that you define. The name of the constructor method is the same as the name of the object type. The parameters of the constructor method are exactly the data attributes of the object type, and they occur in the same order as the attribute definition for the object type. At present, only one constructor method can be defined, and thus you cannot define other constructor methods.