Querying Uncertain Data in Heterogeneous Databases

In heterogeneous databases the user may issue a query to join two relations in di erent databases on the keys However the keys may be incompatible In this paper we extend our results on probabilis tic query processing to consider joining two relations on incompatible keys A new approach to identify the same entities in di erent relations is proposed Various data and schema con icts such as missing data inconsistent data and domain mismatch are considered in the identi cation process Probabilis tic techniques are used to estimate the sameness of two entities to process queries and to estimate the degree of uncertainty for the query results