domingo, 10 de junho de 2007

SATMS - The Simplified Assumption-based Truth Maintenance System

Seminário do Grupo de Lógica, Inteligência Artificial
e Métodos Formais - LIAMF
Seminário Registrado na CPG do IME/USP

Título: SATMS - The Simplified Assumption-based Truth Maintenance System

Palestrante: Tiago Motta Jorge

Data e Local: dia 11.06.07 às 16:00 hs

Local: Sala 242 - Bloco A - IME - USP


Truth maintenance systems (TMS) are mechanisms for keeping track of dependencies and detecting inconsistency. They are also known as a kind of belief revision systems.

Sometimes it is convenient to perform reasoning in the context of different hypothetical worlds, which may or may not resemble the way the world actually is. This strategy is particularly useful if there are a large number of hypotheses competing to account for the observations, with the possibility that a composite hypothesis may be required to cover all of them.

In an assumption-based truth maintenance system (ATMS), the program maintains a number of different contexts, referred to as environments. An environment is best thought of as a view of the world characterized by a set of assumptions.

One can think of the ATMS as being a dynamic structure that maintains dependencies among assumptions. Given a proposition, it can construct a label for that propostion telling in which environments it holds. With this structure, it is straightforward to add and retract assumptions and still be capable to check wheter or not a proposition still holds, without having to make a lot of inferences.

In this seminar, a simplified version of the ATMS will be presented. It assumes that all assumptions are fixed. Besides, it assumes that the inconsistent sets of assumptions are known a priori. The SATMS's job is just to give us one maximal consistent set of assumptions from an inconsistent set.

It will also be presented an application of the SATMS in a programming game called Guntactyx.

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