random graphs in which each of the K(K{1)=2 edges either exists or does not exist in G. Let d jk be the binary indicator that an edge exists connecting S j and S k . An equivalent parameterization specifies that l jk~0 when d jk~0 and l jk w0 otherwise. So, rate matrix L plays an analogous role to the regression coefficients in BSSVS. An important difference is that l jk [ (0, ?) while b k [ ({?, ?), mandating alternative prior formulations.