This research was also partially funded by the Ministry of Economy under grant TIN2009-14715-C04-01 (KNOW2 project).
to generate good quality units for the evaluation the informativeness of items was calculated as follows: in f or mat iveness(i t em) = l eng th(i t em t i t le )/av g L t i t le * log(N /count(i t em t i t l e )) +leng where t i t l e, desc, sub j refer to the title, description and subject fields of the metadata, av g L X is the average length of field X over the whole collection, leng th(i t em X ) is the length of that item field text, and count(i t em X ) gives the frequency of that item field text over the whole collection.