What Is the Expressive Power of Disjunctive Preconditions?

While there seems to be a general consensus about the expressive power of a number of language features in planning formalisms, one can find many different statements about the expressive power of disjunctive preconditions. Using the “compilability framework,” we show that preconditions in conjunctive normal form add to the expressive power of propositional strips, which confirms a conjecture by Backstrom. Further, we show that preconditions in conjunctive normal form do not add any expressive power once we have conditional effects.