The Ninth International Symposium on Logical Formalizations of Commonsense Reasoning
will be held at the Fields Institute for Research in Mathematical Sciences, at the University
of Toronto, on June 1–3, 2009. Since its inception in 1991, the Commonsense Reasoning
Symposium series has provided a forum for exploring one of the long-term goals of
Artificial Intelligence, endowing computers with common sense. Although we know how
to build programs that excel at certain bounded or mechanical tasks which humans find
difficult, such as playing chess, we still have very little idea how to program computers to
do well at commonsense tasks which are easy for humans. One approach to this problem is
to formalize commonsense reasoning using formal languages such as mathematical logic.
The focus of the symposium is on representation rather than on algorithms, and on formal
rather than informal methods.
Twenty-two technical papers, on a variety of topics in commonsense reasoning, including
physical reasoning, planning, theories of action, belief revision, and nonmonotonic
reasoning, are included in these proceedings and will be presented at the symposium. Each
paper was reviewed by at least two members of the program committee.
The program also features invited talks by three leading researchers:
• Anthony G. Cohn (University of Leeds, UK), “Acquiring Commonsense Knowledge
from Perceptual Observation”;
• Ernest Davis (New York University, USA), “Commonsense Reasoning about Chemistry
Experiments: Ontology and Representation”; and
• Sheila McIlraith (University of Toronto, Canada), “Diagnosis Revisited.”
We are pleased to recognize two student papers with the Commonsense-2009 Outstanding
Student Paper Award. Eligible papers had to be authored or co-authored by a student
at the time of submission, and could not be co-authored by any of the Symposium Chairs.
The two Outstanding Student Papers are:
• Shakhil Khan and Yves Lesperance: “A Logical Account of Prioritized Goals and
• Hannes Strass and Michael Thielscher: “Defaults in Action: Nonmonotonic Reasoning
about States in Action Calculi”
We are very pleased that the symposium will be held in Toronto this year, where Ray Reiter
(1939–2002), a world leader in cognitive robotics and formal commonsense reasoning,
spent many years of his life and scientific career. It is with great gratitude for Ray’s lasting
contributions to our field that we dedicate this symposium to his memory.
Organizing such an event always rests on many shoulders. We are especially grateful to
Hojjat Ghaderi, our Local Arrangements Chair, as well as the other members of his team
from the University of Toronto: Luna Keshwah, Hector Levesque, and Sheila McIlraith.
We are equally grateful to our Conference Webmaster, Benjamin Johnston, of the University
of Technology, Sydney, for designing and building the symposium website, managing
the EasyChair conference system, and preparing these proceedings.
The Fields Institute for Research in Mathematical Sciences has been extraordinarily
generous, in providing us the space for the symposium; providing funds for student and
symposium chair travel; managing registration; and publicizing this event. We especially
thank Alison Conway of the Fields Institute for her help in organizing all of these functions.
We also thank the Centre for Quantum Computation and Intelligent Systems at the University
of Technology, Sydney, for its generous support of student travel; and the IBM T.J.
Watson Research Center for partly subsidizing the travel of one of the winners of the Commonsense-
2009 Outstanding Student Paper Award.
This symposium is held in cooperation with AAAI, the Association for the Advancement
of Artificial Intelligence. We thank them for their help in promoting this symposium.