1. A method, implemented by at least one processor, comprising: storing a first factor graph representation of a probability distribution describing at least one first entity and including first factors dependent on one or more of a first set of characteristic variables; storing a second factor graph representation of a probability distribution describing second entities and including second factors dependent on one or more of a second set of characteristic variables, wherein at least one of the second set corresponds to at least one of the first set, and another one of the second set includes an identifier variable representing values from the second entities; and after receiving a request including at least one value for at least one of the first set, solving for an a posteriori probability mass function of the identifier variable, the probability mass function including a set of probability values, using a merged factor graph representation based on the first and second factor graph representations and the at least one value; and identifying, in response to the request, at least one of the second entities corresponding to a highest one of the set of probability values.