In collaboration with Philippe Balbiani (IRIT), Alexandru Baltag (Oxford University), Andreas Herzig (IRIT), Tomohiro Hoshi (Stanford University) and Tiago de Lima (IRIT)
Public announcement logic is an extension of multi-agent epistemic logic with dynamic operators to model the informational consequences of
announcements to the entire group of agents. We propose an extension of
public announcement logic, called arbitrary announcement logic, with a
dynamic modal operator that expresses what is true after arbitrary
announcements. Intuitively, [] phi expresses that phi is true after an
arbitrary announcement psi.
For an example, let us work our way upwards from a concrete
announcement. When an atomic proposition p is true, it becomes known by
announcing it. Formally, in public announcement logic, p & [p] K p. This
is equivalent to:
< p > K p
which stands for 'the announcement of p can be made and after that the
agent knows p'. More abstractly this means that there is a announcement
psi, namely psi = p, that makes the agent know p, slightly more formal:
there is a formula psi such that
< psi > K p
We introduce a dynamic modal operator that expresses exactly that:
<> K p
Obviously, the truth of this expression depends on the model: p has to
be true. In case p is false, we can achieve <> K ~p instead. The formula
<> (K p v K ~p) is valid.
I will present various results for the logic. For more information, see
http://www.cs.otago.ac.nz/staffpriv/hans/publications.html
For ontologies represented as Description Logic Tboxes, optimised DL reasoners are able to detect logical errors, but there is comparatively limited support for resolving such problems. One possible remedy is to weaken the available information to the extent that the errors disappear, but to limit the weakening process as much as possible. The most obvious way to do so is to remove just enough Tbox sentences to eliminate the errors. In this talk I'll propose a tableau-like procedure for finding maximally concept-satisfiable terminologies represented in the description logic ALC. I'll discuss some optimisation techniques, and report on preliminary, but encouraging, experimental results. This is joint work with Kevin Lee, Richard Booth, and Jeff Pan.
Résumé :
"Nous nous sommes intéressés à la fusion de systèmes d'argumentation
<<à la Dung>> afin de pouvoir raisonner à partir de systèmes fournis
par plusieurs agents. Notre approche peut prendre en compte des
systèmes d'argumentation fondés sur des ensembles d'arguments
différents et sur des relations d'attaque différentes.
Nous commençons par rappeler le cadre de Dung. Puis nous présentons
les systèmes d'argumentation partiels introduits dans le but de
prendre en considération les arguments ainsi que les relations
d'attaque des autres agents. Ces systèmes d'argumentation étendent
ceux proposés par Dung en ajoutant une relation d'ignorance entre
arguments. Nous décrivons ensuite le processus de fusion (suivant
un mécanisme similaire à celui employé dans la fusion de bases de
connaissances). Nous terminons notre exposé par l'étude de quelques
propriétés de la fusion.
Ce travail a été effectué en collaboration avec Sylvie Coste-Marquis,
Sébastien Konieczny, Marie-Christine Lagasquie-Schiex et Pierre
Marquis.
"session spéciale" avant-première des presentations à KR et NMR
plus deux invités de passage: