PDDL4J is an open source library under licence LGPL (http://www.gnu.org/licenses/). The purpose of the PDDL4J is to facilitate the java implementation of planners based on the PDDL (Planning Description Language). The library contains a parser on the last version of PDDL 3.0 and all the classes need to manipulate its concepts. The parser can be configured to accept only specified requirements of PDDL langage.