Institute of Computer Science, Martin Luther University Halle-Wittenberg, Halle, Germany. martin.nettling@informatik.uni-halle.de.|Leibniz Institute of Plant Biochemistry, Halle, Germany.|Institut dInvestigació en Intel ·ligència Artificial, IIIA-CSIC, Campus UAB, Cerdanyola, Spain.|Institute of Computer Science, Martin Luther University Halle-Wittenberg, Halle, Germany.