A computer implemented method of ranking items of data stored in a database comprising a plurality of records, wherein each record is associated with one or more items of data. The method includes generating a concordance of the items of data associated with the records in the database. Each record is assigned to a first group of records or to a second group of records. For each item of data a first indicator is determined representative of its occurrences in the records of the first group. For each item of data a second indicator is determined representative of its occurrences in the records of the second group. For each item of data a score is determined representative of a discriminative power of that item of data on the basis of the first and second indicator of that item of data.