Sesión extraordinaria del Seminario (19-10-2009): Tero Tulenheimo

Fecha / Date: 19-10-2009.

Hora / Time: 12:00 h.

Lugar / Location: Seminario de Lógica de la Facultad de Filosofía - Universidad de Sevilla.

Ponente / Lecturer: Tero Tulenheimo (Universidad de Lille3).

Título / Tittle: A survey on IF Modal Logic.

Resumen / Abstract:
A simple variant of IF modal logic -or: independence friendly modal logic- is syntactically obtained from basic modal logic (in negation normal form) by introducing a mechanism by means of which to indicate that a diamond symbol is "independent" of a syntactically preceding box symbol. What does "independent" mean here? It means that when specifying a witness for this diamond symbol, the "semantic value" or "interpretation" corresponding to that box symbol is not available to be used: the witness must be provided by a function that does not employ the state interpreting the box as an argument.
We will present different variants of IF modal logic. Their semantics can be conveniently formulated in game-theoretic terms. In such a setting the above mentioned "independence" appears as "imperfect information" concerning the previous course of a play.
We survey results about the expressive power of variants of IF modal logic when compared to basic modal logic, first-order logic (FO), finite-variable fragments of FO and the guarded fragment of FO. Known complexity results about certain versions of IF modal logic will be mentioned. Finally, we comment on the relationship of IF modal logic and the hybrid logic with \downarrow and @, stressing the difference in the ideas by means of which these two logics increase the expressive power of basic modal logic; some systematic comparative remarks will be presented as well.