Actor Prolog is an object-oriented logic language. So, any program written in Actor Prolog consists of classes. ... An example of Actor Prolog program. -- -- (c) 2002, Alexei A. Morozov, IRE RAS. -- ------------------------------------------- project : (( 'Hello' )) class 'Hello' specializing 'Console': [ goal:- writeln ( "Hello World!" This program consists of solely 'Hello' class. ... Thus, the execution of the program starts with the creation of an instance of the 'Hello' class. ...