GROM is a general rewritter of ontology mappings. Its goal is to manage high-level schema-mappings among ontologies over relational databases. It allows data architects to define high-level mappings between a source and a target ontology, defined as a set of views over the original databases. GROM rewrites these mappings between the virtual descriptions in terms of executable mappings between the two physical databases.
There are two main lessons to be learnt from using the tool. First of all, most of the time it is easier to work with higher-level descriptions than the original database schemas. Secondly, as soon as the visualization language becomes more expressive and can deal, for instance, with negation, the mapping problem becomes extremely challenging from the technical point of view. Consequently, it is necessary to find the appropriate balance between expressiveness and scalability.
The tool can be downloaded from http://www.db.unibas.it/projects/grom/, where you can also find more information.