1. A method comprising: receiving, by a computer processor of a computing device from a plurality of data sources, first health event data associated with a first plurality of heath care records associated with a plurality of patients, said computer processor controlling a cloud hosted mediation system comprising an inference engine software application, a truth maintenance system database, and non monotonic logic; associating, by said computer processor, portions of said first health event data with associated patients of said plurality of patients; associating, by said computer processor, said portions of said first health event data with related records in said truth maintenance system database; deriving, by said computer processor executing said inference engine software application, first health related assumption data associated with each portion of said portions of said first health event data; retrieving, by said computer processor from said truth maintenance system database, previous health related assumption data derived from and associated with previous portions of previous health event data retrieved from said plurality of data sources, said previous health related assumption data derived at a time differing from a time of said deriving, said previous health related event data associated with previous health related events occurring at a different time from said first health event data; executing, by said computer processor, said non monotonic logic with respect to said first health related assumption data and said previous health related assumption data; generating, by said computer processor executing said non monotonic logic and said inference engine software application, first updated health related assumption data associated with said first health related assumption data and said previous health related assumption data; and storing, by said computer processor in said truth maintenance system database, said first assumption health related data and said first updated health related assumption data.