Showing papers in "New Generation Computing in 2001"

Preference queries in deductive databases

Abstract: Traditional database query languages such as datalog and SQL allow the user to specify only mandatory requirements on the data to be retrieved from a database. In many applications, it may be natural to express not only mandatory requirements but also preferences on the data to be retrieved. Lacroix and Lavency10) extended SQL with a notion of preference and showed how the resulting query language could still be translated into the domain relational calculus. We explore the use of preference in databases in the setting of datalog. We introduce the formalism of preference datalog programs (PDPs) as preference logic programs without uninterpreted function symbols for this purpose. PDPs extend datalog not only with constructs to specify which predicate is to be optimized and the criterion for optimization but also with constructs to specify which predicate to be relaxed and the criterion to be used for relaxation. We can show that all of the soft requirements in Reference10) can be directly encoded in PDP. We first develop anaively-pruned bottom-up evaluation procedure that is sound and complete for computing answers to normal and relaxation queries when the PDPs are stratified, we then show how the evaluation scheme can be extended to the case when the programs are not necessarily stratified, and finally we develop an extension of themagic templates method for datalog14) that constructs an equivalent but more efficient program for bottom-up evaluation.

Logic-based genetic programming with definite clause translation grammars

Abstract: DCTG-GP is a genetic programming system that uses definite clause translation grammars. A DCTG is a logical version of an attribute grammar that supports the definition of context-free languages, and it allows semantic information associated with a language to be easily accommodated by the grammar. This is useful in genetic programming for defining the interpreter of a target language, or incorporating both syntactic and semantic problem-specific constraints into the evolutionary search. The DCTG-GP system improves on other grammar-based GP systems by permitting nontrivial semantic aspects of the language to be defined with the grammar. It also automatically analyzes grammar rules in order to determine their minimal depth and termination characteristics, which are required when generating random program trees of varied shapes and sizes. An application using DCTG-GP is described.

Rationality of reward sharing in multi-agent reinforcement learning

Abstract: In multi-agent reinforcement learning systems, it is important to share a reward among all agents. We focus on theRationality Theorem of Profit Sharing 5) and analyze how to share a reward among all profit sharing agents. When an agent gets adirect reward R (R>0), anindirect reward μR (μ≥0) is given to the other agents. We have derived the necessary and sufficient condition to preserve the rationality as follows; $$\mu < \frac{{M - 1}}{{M^W (1 - (\tfrac{1}{M})^{W_o } )(n - 1)L}}$$ whereM andL are the maximum number of conflicting all rules and rational rules in the same sensory input,W andW o are the maximum episode length of adirect and anindirect-reward agents, andn is the number of agents. This theory is derived by avoiding the least desirable situation whose expected reward per an action is zero. Therefore, if we use this theorem, we can experience several efficient aspects of reward sharing. Through numerical examples, we confirm the effectiveness of this theorem.

Constructive negation and constraint logic programming with sets

Abstract: The aim of this paper is to extend theConstructive Negation technique to the case ofCLP(SeT), a Constraint Logic Programming (CLP) language based on hereditarily (and hybrid) finite sets. The challenging aspects of the problem originate from the fact that the structure on whichCLP(SeT) is based is notadmissible closed, and this does not allow to reuse the results presented in the literature concerning the relationships betweenCLP and constructive negation.

Mobile robot navigation by a Distributed Vision System

Abstract: This paper proposes aDistributed Vision System (DVS), which is an intelligent infrastructure for mobile robots consisting of manyvision agents (VAs) embedded in an environment. The system monitors the environment from various viewing points with the VAs, maintains the dynamic environment models, and provides various information to robots. Based on this concept, we have developed a prototype of the DVS which consists of sixteen vision agents and simultaneously navigates two robots in a model town.

Reliable Agent Communication — A pragmatic perspective

Abstract: It is well recognized that Agent Communication Languages (ACL’s) are critical elements of Multi-Agent Systems and a key to their successful application in commerce and industry. The established field ofprotocol engineering, which concerns itself with how to specify machine communication languages and protocols, verify their properties and validate implementations thereof, has developed powerful, theoretical and practical techniques for doing so, and a mature understanding of the essential requirements that such specifications should meet. Regrettably, this body of knowledge and practice appears to have had little influence on recently proposed ACL standards. For example, the latest ACL specifications proposed by the Foundation for Intelligent Physical Agents (FIPA) are a confusing mix of different formal and informal specification techniques whose net result is ambiguous, inconsistent and under-specified. Allowances must be made, as these are still draft specifications, but rather than providing a verified foundation for reliable communication between heterogeneous agents, they run the risk of leading to unreliable or incompatible implementations, or of being ignored in favour of more pragmatic and robust approaches. In this paper, we propose a set of basic requirements which an ACL specification should meet, describe how the FIFA ACL measures up against these, and contrast its features with those of a small ACL which was designed with reliability and ease of verification as prime objectives.

Biomolecular realizations of a parallel architecture for solving combinatorial problems

Abstract: A coherent approach to the problem of carrying out computations in aqueous solution is provided The conceptual level of the presentation provides for many different molecular realizations to be explored in the future Several possibilities are suggested Our initial implementations have provided wet lab prototype computations for two of the classicalNP complete graph theoretic problems: the maximum independent set problem and the minimum dominating set problem A wet lab prototype computation is in progress for the determination of the satisfiability of sets of disjunctive clauses

Trends of Internet auctions and agent-mediated Web commerce

Abstract: Electronic Commerce (EC) is a promising field for applying agent and Artificial Intelligence technologies. In this article, we give an overview of the trends of Internet auctions and agent-mediated Web commerce. We describe the theoretical backgrounds of auction protocols and introduce several Internet auction sites. Furthermore, we describe various activities aimed toward utilizing agent technologies in EC and the trends in standardization efforts on agent technologies.

From eager to lazy constrained data acquisition: a general framework

Abstract: *1 Constraint Satisfaction Problems (CSPs)17) are an effective framework for modeling a variety of real life applications and many techniques have been proposed for solving them efficiently. CSPs are based on the assumption that all constrained data (values in variable domains) are available at the beginning of the computation. However, many non-toy problems derive their parameters from an external environment. Data retrieval can be a hard task, because data can come from a third-party system that has to convert information encoded with signals (derived from sensors) into symbolic information (exploitable by a CSP solver). Also, data can be provided by the user or have to be queried to a database.

Temporal disjunctive logic programming

Abstract: In this paper we introduce the logic programming languageDisjunctive Chronolog which combines the programming paradigms of temporal and disjunctive logic programming. Disjunctive Chronolog is capable of expressing dynamic behaviour as well as uncertainty, two notions that are very common in a variety of real systems. We present the minimal temporal model semantics and the fixpoint semantics for the new programming language and demonstrate their equivalence. We also show how proof procedures developed for disjunctive logic programs can be easily extended to apply to Disjunctive Chronolog programs.

Blackboard relations in the mLog coordination model

Abstract: This paper describescoordination relations, that are relations that induce the presence or absence of data on some dataspaces from the presence or absence of other data on other dataspaces.

Information gathering and searching approaches on the Web

Abstract: The information accessible through the Internet is increasing explosively as the Web is getting more and more widespread. In this situation, the Web is indispensable information resource for both of information gathering and information searching. Though traditional information retrieval techniques have been applied to information gathering and searching in the Web, they are insufficient for this new form of information source. Fortunately some Al techniques can be straightforwardly applicable to such tasks in the Web, and many researchers are trying this approach. In this paper, we attempt to describe the current state of information gathering and searching technologies in the Web, and the application of AI techniques in the fields. Then we point out limitations of these traditional and AI approaches and introduce two aapproaches: navigation planning and a Mondou search engine for overcoming them. The navigation planning system tries to collect systematic knowledge, rather than Web pages, which are only pieces of knowledge. The Mondou search engine copes with the problems of the query expansion/modification based on the techniques of text/web mining and information visualization.

Facts, arguments, annotations and reasoning

Abstract: Reasoning aboutfacts and reasoning aboutarguments regarding facts are distinct activities, and automated reasoning systems should be able to treat them accordingly. In this work, we discuss one precise sense in which this distinction can be envisaged and suggest the use of Annotated Logics to characterise it.

Multiagent learning towards RoboCup

Abstract: This article describes the issues in multiagent learning towards RoboCup,1≈3) especially for the real robot leagues. First, the review of the issue in the context of the related area is given, then related works from several viewpoints are reviewed. Next, our approach towards RoboCup Initiative is introduced and finally future issues are given.

Web security: Authentication protocols and their analysis

Abstract: Authentication is one of the basic building blocks of computer security. It is achieved through the execution of an authentication protocol between two or more parties. One such protocol, the Secure Socket Layer (SSL) protocol, has become the de facto standard for Web security. This paper provides an overview of results and methods used in analyzing authentication protocols. The aim is to provide a bird’s eye view of the assumptions, methods, and results that are available for anyone who is interested in designing new security protocols or applying a new analysis approach. A detailed description of the SSL handshake protocol as well as how changes in environment assumption can lead to unexpected consequences, is provided. A fix to the weakness is also described.

Cooperation of categorical and behavioral learning in a practical solution to the abstraction problem

Abstract: Real robots should be able to adapt autonomously to various environments in order to go on executing their tasks without breaking down. They achieve this by learning how to abstract only useful information from a huge amount of information in the environment while executing their tasks. This paper proposes a new architecture which performs categorical learning and behavioral learning in parallel with task execution. We call the architectureSituation Transition Network System (STNS). In categorical learning, it makes a flexible state representation and modifies it according to the results of behaviors. Behavioral learning is reinforcement learning on the state representation. Simulation results have shown that this architecture is able to learn efficiently and adapt to unexpected changes of the environment autonomously.