The following page offers details of requirements defined in PDDL 2.2.
Allows the usage of derived predicates in domains. e.g.
(:derived (train-usable ?t - train) (and (train-has-guard ?t) (train-has-driver ?t) ) )
Allows the use of Timed Initial Literals when defining problems. e.g.
(at 10 (train-not-in-use t1))