The only difference in the level of data in relation to the entire program. Everything is an object with specific characteristics and behaviors. Objects use messages to communicate to each other. The only thing that an object knows about another object is the other object' s interface. Private data members and methods are hidden.
Objects can inherit the characteristics and behaviors from parent objects.
This violates the principles of information hiding and may lead to unintended side-effects. In comparison Prolog has a certain type of object relation called a selector which allows the user to access certain components of a family of objects with the full details of it. The name of the selector is that of the component being selected. These relations allow us to ignore the amount of the information in the object family. We only need to know the name of the selector relations.