1. A method for ranking a data set of objects comprising: providing a graph representing the data set; providing examples of ranking preferences for a portion of objects in the data set, each of said examples indicating a ranking of a first object of the portion with respect to a second object of the portion; determining, in accordance with said examples, a function, f, that ranks the objects of the data set; and determining a ranking of the objects of the data set using said function, f.