Relatedness Measures

Lesk

The Lesk measure works by finding overlaps in the extended definitions of the two concepts. The relatedness score is the sum of the squares of the overlap lengths. For example, a single word overlap results in a score of 1. Two single word overlaps results in a score of 2. A two word overlap (i.e., two consecutive words) results in a score of 4. A three word overlap results in a score of 9.

Vector

The vector measure works by forming second-order co-occurrence vectors from the UMLS extended definitions of concepts. The relatedness of two concepts is determined as the cosine of the angle between their vectors.