A method of operating a database management system for integrating data from a plurality of data sources comprising steps of: (a) selecting initial attributes for first and second data sources; (b) selecting a candidate matching function relating to a possible mapping between data in said first and second data sources; (c) applying said candidate matching function to data in said first data source to create possible data for said second data source; (d) deriving a disparity measure relating to an amount of disparity therebetween; (e) selecting different candidate matching functions and repeating steps (c) and (d); (f) designating a candidate matching function having a disparity measure indicative of the lowest amount of disparity as a probable candidate matching function; (g) selecting further attributes and performing steps (b) to (f) in respect thereof; and (h) determining a probable correspondence between data objects of said first and second data sources.