A method, system and computer program product provides a first characteristic associated with a first data set and a single data value, and a second characteristic associated with a second data set; and calculates at least one of: 1) the similarity of the first data set with the second data set based on the first and second characteristics, 2) the similarity of the first data set with the single data value based on the first characteristic and the single data value, 3) confidence indicating how well the first characteristic reflects properties of the first data set based on the first characteristic, and 4) confidence indicating how well the similarity of the first data set with the single data value reflects properties of the single data value based on the first characteristic and the single data value.