1. A processor-implemented method of inversing a schema mapping in a computer, comprising: identify in a source schema comprising a finite sequence of distinct relation symbols having a plurality of source relations, wherein each of the distinct relation symbols of the source schema has a fixed arity; for each source relation, creating a source relation instance for each of the distinct relation symbols, resulting in a plurality of source relation instances comprising an instance sequence of the distinct relation symbols with the fixed arity of the source schema; chasing each source relation instance using the schema mapping to generate a plurality of target relations in a target schema; and generating an inverse schema mapping in the computer by mapping the plurality of target relations from the target schema to the source relation instances of the source schema.