| | All
sessions take place in auditorium 7.09:00- | 09:30
| Michael Schroeder, City U, London,
UK Ralf
Schweimeier, City U, London, UK
**Arguments
and misunderstandings: Fuzzy unification for negotiating
agents** In
this paper, we develop the notion of fuzzy unification and
incorporate it into a novel fuzzy argumentation framework for extended
logic programming. We make the following contributions: The argumentation
framework is defined by a declarative bottom-up fixpoint semantics and an
equivalent goal-directed top-down proof-procedure for extended logic
programming. Our framework allows one to represent positive and explicitly
negative knowledge, as well as uncertainty. Both concepts are used in agent
communication languages such as KQML and FIPA ACL. One source of
uncertainty in open systems stems from mismatches in parameter and
predicate names and missing parameters. To this end, we conservatively
extend classical unification and develop fuzzy unification based on
normalised edit distance over trees. |
09:30- | 10:00
| João Alexandre
Leite, New U of Lisbon, Portugal José
Júlio Alferes, New U of Lisbon, Portugal Luís
Moniz Pereira, New U of Lisbon, Portugal Halina
Przymusinska, Cal Poly Pomona, USA Teodor
C. Przymusinski, U California-Riverside, USA
**A
language for multi-dimensional updates** Dynamic
Logic Programming (DLP) was introduced to deal with
knowledge about changing worlds, by assigning semantics to sequences of
generalized logic programs, each of which represents a state of the world.
These states permit the representation, not only of time, but also of
specificity, strength of updating instance, hierarchical position of the
knowledge source, etc. Subsequently, the Language of Updates LUPS was
introduced to allow for the association, with each state, of a set of
transition rules. It thereby provides for an interleaving sequence of
states and transition rules within an integrated declarative framework. DLP
(and LUPS), because defined only for a linear sequence of states, cannot
deal simultaneously with more than a single dimension (e.g. time,
hierarchies,...). To overcome this limitation, Multi-dimensional Dynamic
Logic Programming (MDLP) was therefore introduced, so as to make it
possible to organize states into arbitrary acyclic digraphs (DAGs). In this
paper we now extend LUPS, setting forth a Language for Multi-dimensional
Updates (MLUPS). MLUPS admits the specification of flexible evolutions of
such DAG organized logic programs, by allowing not just the specification
of the logic programs representing each state, but to the evolution of the
DAG topology itself as well. |
10:00- | 10:30
| Antonis C. Kakas, U Cyprus Pavlos
Moraitis, U Cyprus
**Argumentative
agent deliberation, roles and context** This
paper presents an argumentation based framework to support
an agent's deliberation process for drawing conclusions under a given
policy. The argumentative policy of the agent is able to take into account
the roles agents can have within a context pertaining to an environment of
interaction. |
11:00- | 11:30
| Katsuhiko Toyama, Nagoya U, Japan Takahiro
Kojima, Nagoya U, Japan Yasuyoshi
Inagaki, Nagoya U, Japan
**Translating
multi-agent autoepistemic logic into logic
program** Multi-agent
autoepistemic Logic (MAEL) is a natural framework to
formalize beliefs and reasoning including inheritance, persisitence, and
causality. To develop a proof procedure of it, we introduce a method that
translates a MAEL theory into a logic program with integrity constraints.
We also investigate relations between MAEL and other nonmonotonic
reasonings. |
11:30- | 12:00
| Pierangelo Dell'Acqua, Linköping
U, Sweden Ulf
Nilsson, Linköping U, Sweden Luís
Moniz Pereira, New U of Lisbon, Portugal
**A
logic based asynchronous multi-agent system** We
present a logic programming based asynchronous multi-agent
system in which agents can: communicate with one another; update themselves
and each other; eliminate contradictory update rules; abduce hypotheses to
explain observations, and use them to generate actions. The knowledge base
of the agents is comprised of generalized logic programs, integrity
constraints, active rules, and of abducibles. We characterize the
interaction among agents via an asynchronous transition rule system, and
provide a stable models based semantics. An example is developed to
illustrate how our approach functions. |
12:00- | 12:30
| James Harland, RMIT U, Australia Michael
Winikoff, RMIT U, Australia
**Language
design issues for agents based on linear logic (extended
abstract)** Agent
systems based on the *Belief*, *Desire* and *Intention* model
of Rao and Georgeff
have been used for a number of successful applications. However, it is
often difficult to learn how to apply such systems, due to the complexity
of both the semantics of the system and the computational model. In
addition, there is a gap between the semantics and the concepts that are
presented to the programmer. One way to bridge this gap is to re-cast the
foundations of such systems into a logic programming framework. In
particular, the integration of backward- and forward-chaining techniques
for linear logic provides a natural starting point for this investigation.
In this paper we discuss the language design issues for such a system, and
particularly the way in which the potential choices for rule evaluation in
a forward-chaining manner is crucial to the behaviour of the
system. |
14:00- | 14:30
| Rafael H. Bordini, Federal U of Rio Grande
do Sul, Brazil Álvaro
F. Moreira, U Caxias do Sul, Brazil
**Proving
the asymmetry thesis principles for a BDI agent-oriented
programming language** In
this paper, we consider each of the nine principles of BDI
logics as defined by Rao and Georgeff based on Bratman's asymmetry thesis,
and we verify which ones are satisfied by Rao's AgentSpeak(L), a computable
logic language inspired by the BDI architecture for cognitive agents. This
is in line with Rao's original motivation for defining AgentSpeak(L): to
bridge the gap between theory and practice of BDI agent systems. In order
to set the grounds for the proof, we first introduce a particular way in
which to define the informational, motivational, and deliberative
modalities of BDI logics for AgentSpeak(L) agents, according to its
structural operational semantics (that we introduced in a recent paper).
This provides a framework that can be used to investigate further
properties of AgentSpeak(L) agents, contributing towards giving firm
theoretical grounds for BDI agent programming. |
14:30- | 15:00
| Tadashi Araragi, NTT Communication
Science Laboratories, Japan Shiro
Takata, ATR Media Information Science Laboratories, Japan Naoyuki
Nide, Nara Women's U, Japan
**A
verification method for a commitment strategy of the BDI
architecture** We
present a method to solve a verification problem that arises
in implementing a commitment strategy for the BDI architecture. This
problem introduces a new aspect of verification such that a state
transition depends on a verification done at each state. We formalize this
problem and give a decision procedure for the verification. |
15:00- | 15:30
| Naoyuki Nide, Nara Women's U, Japan Shiro
Takata, ATR Media Information Science Laboratories, Japan Tadashi
Araragi, NTT Communication Science Laboratories, Japan
**Deduction
systems for BDI logics with mental state
consistency** BDI
Logics, introduced by Rao et al., have been used as the
theoretical basis of specification and implementation of rational agents.
The aim of our research is to make full use of the expressive power of BDI
Logics as executable specification languages of rational agents. To this
end, we previously presented deduction systems for CTL-based propositional
BDI Logics using sequent calculus. Since these systems have a decision
algorithm that is extended from Wang's algorithm, they are suitable for
applications such as automatic proving. However, they do not incorporate
mental state consistency features, which are important for dealing with
rational agents. In this paper, we extend our deduction systems by
introducing mental state consistency features and explain their soundness
and completeness. This approach allows us to check and prove the
specifications and properties described by BDI Logics for rational
agents. |
16:00- | 16:30
| Hisashi Hayashi, Toshiba, Japan Kenta
Cho, Toshiba, Japan Akihiko
Ohsuga, Toshiba, Japan
**Speculative
computation and action execution in multi-agent
systems** In
some multi-agent systems, when an agent cannot retrieve
information from another agent, the agent makes an assumption and
tentatively performs the computation. When the agent comes across a mistake
in the preliminary assumption, the computation is modified. This kind of
speculative computation is effective when the assumption is correct.
However, once the agent executes an action, it is impossible to modify the
computation in these systems. This paper shows how to integrate speculative
computation and action execution through logic programming. |
16:30- | 17:00
| Koji Iwanuma, Yamanashi U, Japan Katsumi
Inoue, Kobe U, Japan
**Conditional
answer computation in SOL as speculative computation in
multi-agent environments** In
this paper, we study speculative computation in a master-slave
multi-agent system where reply messages sent from slave agents to a master
are always tentative and may change from time to time. In this system,
default values used in speculative computation are only partially
determined in advance. Inoue *et al.* [2001] formalized speculative
computation in such an
environment with tentative replies, using the framework of a first-order
consequence-finding procedure SOL with the well-known answer literal
method. We shall further refine SOL calculus, using *conditional
answer* computation and *skip-preference* in SOL. The conditional
answer format has an great advantage of
explicitly representing the dependency relation to tentative replies and
defaults which are used to derive a conclusion. The dependency
representation is significantly important to avoid unnecessary
recomputation of tentative conclusions. The skip-preference has the great
ability of preventing irrational/redundant derivations. Finally, we show an
incremental answer computation method within the SOL tableau
calculus. |
17:00- | 17:30
| Thomas Bolander, Techn. U of Denmark
**Maximal
introspection of agents** This
paper concerns syntactical representations of introspective
belief and knowledge in multi-agent systems. It is well-known that
reasoning frameworks for introspective beliefs easily become inconsistent
as a consequence of the presence of paradoxical self-reference. In the
paper we explore the maximal sets of introspective beliefs that an agent
can consistently obtain and retain. Hereby some previous results by Perlis
[1985] and Rivière &
Levesque [1988] are generalized. |
*Chair:*
Paolo Torroni
| |