And in improved GVSM (Farahat and Kamel, 2010), the best which is covariance matrix of terms is calculated as 4where is random sample of and 5maps uncorrelated terms to nearorthogonal directions and negatively correlated terms to opposite directions in the semantic space, while traditional maps both uncorrelated terms and negatively correlated terms to nearorthogonal directions.
we use cosine similarities between term vectors in case of as one of our similarity measures.