which is a VA II where it's prior is P of Z 2 which is another V and so on so these are two equivalent ways of looking at the same model so in terms of log likelihood they're the same because that if you just write down v variational bounds they're equal but they suggest slightly different compression algorithms with different practical consequences so the idea is that instead of just treating disease as one single block of one large latent variable you can actually recursively invoke its back coding into the prior so you can just