Lin defined the commonality between A and B as )) , ( (  B  A  common  I where common(A, B) is a proportion that states the commonalities between A and B and where the amount of information in proposition s is The similarity between A and B is then defined as the ratio between the amount of information needed to state the commonality of A and B and the information needed to fully describe A and B: In order to compute common(A,B) and description(A,B), we use standard bag-of-words features, i.e., unigram features --the frequency of words computed from the entire corpus of the skill statements.
common(A,B) is the unigrams that both skill statements share, and description(A,B) is the union of the unigrams from both skill statements.