34 Chapter 2 Representations for Classical Planning
2.4 Extending the Classical Representation
Since the classical planning formalism is very restricted, extensions to it are needed in
order to describe interesting domains. It is possible to extend the classical planning
formalism, while staying within the same model of restricted state-transition sys-
tems, by allowing expressions that are more general than just collections of literals
in the preconditions and effects of the operator, as well as in the descriptions of
states. The following subsections discuss several examples.
2.4.1 Simple Syntactical Extensions
One of the simplest extensions is to allow the goal formula g to be any existentially
closed conjunct of literals, such as ∃x ∃y(on(x, c1 ...