In this poster we tackle the problem of aligning large ontologies where the mappings suggested by the ontology alignment system need to be validated. In contrast to the case of small ontologies; the computation of mapping suggestions can take a long time and therefore; we would like to be able to start the validation before every mapping suggestion is computed. Further; it is clear that for large ontologies; in general; there are too many mapping suggestions to validate in one time. Therefore; we want a system that allows to partially validate the mapping suggestions and resume the validation later. However; whenever validation decisions have been made; they increase our knowledge about the ontologies and mappings and this knowledge can be used to provide better mapping suggestions.