Object based language have been widely in many areas. However, Prolog is a language for symbolic, non-numeric computation. Its syntax is a modified version of predicate Calculus. It is good for solving problems with objects and relationships between them. Prolog allows us to ask questions based on the relationship between each others objects.
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. An object can also inherit attributes from parent objects. Smalltalk is a truly object based language. All of data types are objects.