Membership Details (University/College)
Contact: Stefania Costantini
Member node: 123
via Vetoio Loc. Coppito, I-67010 L'Aquila, Italy
Italy
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Description
Recently, a new programming language, called DALI, for the definition oflogical agents and multi-agent systems has been proposed (by Stefania Costantini) at the Computer Science Dept. of the University of L'Aquila. The language has been implemented (in co-operation with Arianna Tocchio and other students) and is being experimented on some real-world applications.
Syntactically, DALI is
close to the Horn clause language and to Prolog. DALI programs, i.e., DALI agents, may however contain a new kind of rules, reactive rules, aimed at:
(i) interacting with an external environment; (ii) reacting to some of its own internal conclusions. The environment is perceived in the form of external events, that can be exogenous events, observations, or messages from other agents. In response, a DALI agent can either make actions or send messages, or perform some internal reasoning.
What is new in DALI is that the same external event can be considered under different points of view: the event is first perceived, and the agent may reason about this perception; then a reaction can take place, and finally the event and the (possible)
actions that have been performed are recorded as past events and
past actions. An important novel feature is that internal conclusions can be seen as events: this means, a DALI agent can "think" about some topic, the conclusions she takes can
determine a behavior, and, finally, she is able to remember the conclusion, and what she did in reaction. Distinguished internal conditions that can trigger reactions are automatically attempted from time to time. Whatever the agent remembers is kept or "forgotten" according to suitable
conditions (that can be set by directives). Then, a DALI
agent is not a purely reactive agent based on condition-action rules: rather, it is a reactive, proactive and rational agent that performs inference within an evolving context.
In the evolutionary semantics of the language, the meaning of a given DALI program P is defined in terms of a modified program Ps, where reactive and proactive rules are reinterpreted in terms of standard Horn Clause rules. The agent reception of an event is formalized as a program transformation step. The evolutionary semantics consists of a sequence of logic programs, resulting from this subsequent transformations, together
with the sequence of the Least Herbrand Model of these programs.
Therefore, this makes it possible to model an evolving agent
incorporating an evolving context. In this way, it is possible to
reason about the conclusions reached and the actions performed at
a certain stage, or, better, in a certain context.
DALI has been recently equipped with a communication architecture, that provides filters on incoming and outcoming message, and a meta-reasoning mechanism for "understanding" message contents, possibly by applying ontologies.
The DALI language might constitute a starting point towards the specification of rule-based agents for the semantic web: DALI in fact provides reactive and proactive
features combined with reasoning mechanisms, within an evolving
context that can be exploited for achieving agents with "ambient
intelligence". In fact, work is under way for integrating DALI with the Lixto System, which is a semi-automatic wrapper generator. DALI agents can embed Lixto wrappers, so as to exploit them flexibly, according to a user's needs.
This list was generated on Mon Sep 10 16:39:30 BST 2007. |
