Output arcs are representedby objects of class OutputArc and containing references to their destination places and inscriptions. The inscriptions are represented by objects implementing the IExpression interface that defines method called process. The method receives binding of the transition being fired as an argument, and returns collection of tokens (class Token) that should be put in the output place as a result of transition firing. The process method can perform any desired operations on tokens and their contents. BasicOutputArcExpression class provides means to define simple expressions analogous to the ones used for input arcs.