Tabular representation of schema mappings of a data exchange system

Data exchange is the problem of taking data structured under a source schema and translating them into data structured under a target schema. In data exchange, a target instance is materialized that conforms to the source data as much as possible. A schema mapping is a high-level specification that describes the relationship between two database schemas. Schema mappings constitute essential building blocks of data exchange and data integration systems. Global-and-local-as-view (GLAV) is one of the approaches for specifying the schema mappings. In our earlier work we showed that GLAV mappings of a data integration system can be expressed by tabular structures which we called schema mapping tableaux (SMT). SMT can be used as an operator on an instance of the source schema to produce an instance of the global schema of a data integration system. In this paper, we show that GLAV mappings of a data exchange system can also be represented by SMT. Moreover, SMT can be used to compute target instances of a data exchange system which are `minimal´ and `most general´ in nature.