LinkLDA, however, is more flexible; rather than requiring both arguments to be generated from one of |Z| possible pairs of multinomials (β z , γ z ), Lin-kLDA allows the arguments of a given extraction to be generated from |Z| 2 possible pairs.
instead of imposing a hard constraint that z 1 = z 2 (as in JointLDA), LinkLDA simply assigns a higher probability to states in which z 1 = z 2 , because both hidden variables are drawn from the same (sparse) distribution θ r .