A key disadvantage of the CMM is that it makes critical statements about independence that the HMM does not: the converging arrows at each tag put the parent nodes (the previous tag and the current observation) into causal competition and as a result the model states that the previous tag is independent of the current observation.
the observed-child node, c i , now has three parents: the tags s i−1 , s i , and s i+1 .