Class hierarchies are implemented by denoting within an class who its parents are. The inheritance of methods and attributes is governed by this relationship. Prolog++ supports multiple inheritance by multiple declarations of parenthood.

Prolog++ supports both static and dynamic objects. Dynamic objects can be created or augmented at run-time, while static objects are fixed and optimized at compile time.

A class is a template which defines the general characteristics of its instances and those of any of its sub-classes, sub-sub-classes etc...

Prolog++ supports the use of different methods in different classes which can handle the same message. This follows the common view of polymorphism.

• single message to a group of instances
• group of messages to a single instance
• group of messages to a group of instances

Class definitions in Prolog++ are delimited by key words for their beginning and ending. All the methods and attributes within these two statements are encapsulated. The name of the class and the names of any public methods and attributes form the abstract of that class. Methods are implemented as Prolog clauses, and can be viewed or edited from within the base Prolog environment. Methods can be defined as public or private, have multiple definitions and be truly dynamic, i.e. they can be augmented at run-time.

• create a new class instance
• delete an existing class instance
• assign a new value to a class/instance attribute
• raise a program exception

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