Extensional Knowledge for semantic query optimization in a mediator based system
Domenico Beneventano, Sonia Bergamaschi, Federica Mandreoli · 2001
Query processing in global info/O4b/) systems integrating multiple hetero)kxx4b sotero is a challenging issue in relatio to the e#ectiveextractio o f information availableo n-line. In this paper we pro oo intelligent,to owq)) owq techniquesfo querying glo#j infow matio systems integrating bo th structured and semistructured data so4/Oww The techniques have been develo ed in the enviroxw( t o a data integratio/ wrapper/mediato based system, MOMIS, and tryto achieve thegow o optimiz d query reformulation w.r.t lo calso/xk/j The develo ed techniques relyo the availabilityo f integration knowledgewhoj semantics is expressed in termso descriptio lo/#jw Integratio kno wledge includes lo calsow)j schemata, a virtual mediated schema and its mapping descriptions, that is semantic mappings w.r.t. the underlyingsoderl bo th at the intensional and extensional level. Mappingdescriptio(4 o btained as a resulto the semi-autoOqjq integratio pro cesso f multiple hetero4bq/wj soero develo edfo the MOMIS system, include, unlike previo) data integratio pro o sals, extensional intra/interschema knowledge.