File comparing device includes a comparator for comparing a first and second content identifiers, of respective files, with each other. Each file having at least two content identifiers and each content identifier is defined by at least one parameter. In addition a selector is included for selecting, using the parameters of the content identifiers, sub-groups of content identifiers, to increase flexibilities. Calculators calculate functions of the values of the parameters and further comparators compare the functions with thresholds. Content identifiers may be defined by cost and accuracy parameters. Then, calculators calculate first functions of the values of the cost parameters and calculate second functions of the values of the accuracy parameters and further comparators compare the first functions with first thresholds and compare the second functions with second thresholds.