It is defined as: where P (c, v) = d∈Z P (d)P (c|d)P (v|d), C is the set of concepts in T , V is the set of nonstopwords in Z, and d is a document in Z. EMIM only evaluates the content of a browsing taxonomy, not its structure.
it is still popularly used to indicate how representative a browsing taxonomy is for a document collection.