  The other leading figure in logic who birthed a research tradition was Carlos Alchourrón. Besides his contribution in deontic  logic[43], Alchourrón was also one of the first logicians to develop a logical system for belief dynamics (AGM). The key notions of this theory are revision (when we introduce a new piece of information into the current epistemic state and readjust the background information in such a way that the new result is consistent), and contraction (when a piece of information is eliminated from an epistemic state) (Arló-Costa and Fermé 2010: 483). Developments produced by Alchourrón and collaborators (until his early death in 1996) included issues related to non-monotonic logic and developments in artificial  intelligence.[44]