Checking Containment of Schema Mappings (Preliminary Report)

3rd Alberto Mendelzon International Workshop on Foundations of Data Management

Andrea Calì ; Riccardo Torlone

Others  :  http://CEUR-WS.org/Vol-450/paper13.pdf
PID  :  4424

来源: CEUR

【 摘 要 】

In data exchange, data are materialised from a source schema to a target schema, according to suitable source-to-target constraints. Constraints are also expressed on the target schema to represent the do- main of interest. A schema mapping is the union of the source-to-target and of the target constraints. In this paper, we address the problem of containment of schema mappings for data exchange, which has been re- cently proposed in this framework as a step towards the optimization of data exchange settings. We refer to a natural notion of containment that relies on the behaviour of schema mappings with respect to con- junctive query answering, in the presence of so-called LAV TGDs as target constraints. Our contribution is a practical technique for testing the containment based on the existence of a homomorphism between special “dummy” instances, which can be easily built from schema map- pings. We argue that containment of schema mappings is decidable for most practical cases, and we set the basis for further investigations in the topic. This paper extends the preliminary results of [4].