The standard propositional exposition of necessary and sufficient conditions, as available in introductory logic texts, leads to a contradiction. It should be abolished.

Department of Computer Engineering, Bilkent University, 06533 Ankara, Turkey E-mail: akman@cs.bilkent.edu.tr; http://www.cs.bilkent.edu.tr/?akman..

The Turing Test is one of the most disputed topics in artificial intelligence, philosophy of mind, and cognitive science. This paper is a review of the past 50 years of the Turing Test. Philosophical debates, practical developments and repercussions in related disciplines are all covered. We discuss Turing's ideas in detail and present the important comments that have been made on them. Within this context, behaviorism, consciousness, the `other minds' problem, and similar topics in philosophy of mind are discussed. We (...) also cover the sociological and psychological aspects of the Turing Test. Finally, we look at the current situation and analyze programs that have been developed with the aim of passing the Turing Test. We conclude that the Turing Test has been, and will continue to be, an influential and controversial topic. (shrink)

This is the guest editor's introduction to a JETAI special issue on philosophical foundations of AI.

Strawson proposed in the early seventies an attractive threefold distinction regarding how context bears on the meaning of `what is said' when a sentence is uttered. The proposed scheme is somewhat crude and, being aware of this aspect, Strawson himself raised various points to make it more adequate. In this paper, we review the scheme of Strawson, note his concerns, and add some of our own. However, our main point is to defend the essence of Strawson's approach and to recommend (...) it as a starting point for research into intended meaning and context. (shrink)

The importance of contextual reasoning is emphasized by various researchers in AI. (A partial list includes John McCarthy and his group, R. V. Guha, Yoav Shoham, Giuseppe Attardi and Maria Simi, and Fausto Giunchiglia and his group.) Here, we survey the problem of formalizing context and explore what is needed for an acceptable account of this abstract notion.

P.F. Strawson proposed in the early seventies a threefold distinction regarding how context bears on the meaning of ¿what is said¿ when a sentence is uttered. The proposal was somewhat tentative and, being aware of this aspect, Strawson himself raised various questions to make it more adequate. In this paper, we review Strawson¿s scheme, note his concerns, and add some of our own. We also defend its essence and recommend it as an insightful entry point re the interplay of intended (...) meaning and context. (shrink)

Situation theory has been developed over the last decade and various versions of the theory have been applied to a number of linguistic issues. However, not much work has been done in regard to its computational aspects. In this paper, we review the existing approaches towards `computational situation theory' with considerable emphasis on our own research.

The notion of context arises in assorted areas of artificial intelligence (AI), including knowledge representation, natural language processing, intelligent information retrieval, etc. Although the term ‘context’ is frequently employed in descriptions, explanations, and analyses of computer programs in these areas, its meaning is frequently left to the reader’s understanding. In other words, it is used in an intuitive manner. In an influential paper, Clark and Carlson (1981) state that context has become a favourite word. They then complain that the denotation (...) of the word has become murkier as its uses have been extended in many directions, making context some sort of ‘conceptual garbage can.’. (shrink)

This is a review of Lingustic Semantics: An Introduction, by John Lyons, published by Cambridge University Press in 1995.

In its most common linguistic use, speci city refers to a kind of de niteness. This is expressed by the grammatical marking on an NP, showing that the speaker knows the identity of the referent. Thus, a police chief has (presumably) a particular Colombian in mind when he utters \My agents cannot wait to interrogate the Colombian.".

This is a review of the above title published by Ablex Publishing Corporation, Norwood, New Jersey, 1990; vi + 256 pages, hardback, ISBN 0{89391{535{1 (Library of Congress: Q335.M38 1989), edited by Vladimir Lifschitz.

At the heart of natural language processing is the understanding of context dependent meanings. This paper presents a preliminary model of formal contexts based on situation theory. It also gives a worked-out example to show the use of contexts in lifting, i.e., how propositions holding in a particular context transform when they are moved to another context. This is useful in NLP applications where preserving meaning is a desideratum.

Answer Set Programming is a new paradigm based on logic programming. The main component of answer set programming is a system that finds the answer sets of logic programs. During the computation of an answer set, systems are faced with choice points where they have to select a literal and assign it a truth value. Generally, systems utilize some heuristics to choose new literals at the choice points. The heuristic used is one of the key factors for the performance of (...) the system. A new heuristic for answer set programming has been developed. This heuristic is inspired by hierarchical planning. The notion of criticality, which was introduced for generating abstraction hierarchies in hierarchical planning, is used in this heuristic. The resulting system (CSMOD- ELS) uses this new heuristic in a static way. CSMODELS is based on the system SMODELS. The experimental results show that this new heuristic is promising for answer set programming. A comparison of search times with SMODELS demonstrate CSMODELS’ usefulness. (shrink)

This is a review of Quantifiers, Logic, and Language, edited by Jaap van der Does and Jan van Eijk, published by CSLI (Center for the Study of Language and Information) Publications in 1996.

In this special issue of Minds and Machines ("Situations and Artificial Intelligence") we take a close look at recent situation-theoretic research which has mostly originated within a philosophical framework but promises to have strong connotations for Artificial Intelligence workers. The seven papers which make up this special issue (three of the papers appear in Minds and Machines 9(1)) demonstrate the advantages of the situation-based approach towards problems with a definite AI flavor.

In our routine communicative activities, context is exploited both in production and in comprehension, and is strictly related to another problematic notion, viz. meaning. Thus Bateson (1979: 15): ‘‘Without context, words and actions have no meaning at all. This is true not only of human communication in words but also of all communication whatsoever, of all mental process, of all mind, including that which tells the sea anemone how to grow and the amoeba what he should do next.’’.

This is a review of Vicious Circles: On the Mathematics of Non-Wellfounded Phenomena, by Jon Barwise and Lawrence Moss, published by CSLI Publications in 1996.

Analogical Natural Language Processing aims to challenge the current hegemony of the rulebased paradigm in NLP. Traditional NLP decomposes languages into atomic units, whereas example-based NLP centres around the re-use of language fragments. The book consists of six chapters : a short introduction, chapters on background material, analogical machine translation, stochastic and analogy-based NLP, some experiments in analogical cloning and a conclusion. We shall now look at the chapters more closely.

The success of set theory as a foundation for mathematics inspires its use in arti cial intelligence, particularly in commonsense reasoning. In this survey, we brie y review classical set theory from an AI perspective, and then consider alternative set theories. Desirable properties of a possible commonsense set theory are investigated, treating di erent aspects like cumulative hierarchy, self-reference, cardinality, etc. Assorted examples from the ground-breaking research on the subject are also given.

Here, S is a sentence—or possibly a smaller or larger unit of meaningful expression for a language—that’s written by an author and c is the circumstance in which S is used. R is defined as the language conventions holding between an author and a reader (or better yet, his readership). P , probably the most important part of the equation, is the content of S or, the intended meaning of the author. We assume that the communication between an author and (...) a reader is limited only to written text. Consequently, it is not possible to ask the author about his intention for writing S; that will have to be discovered by a reader. (shrink)

This position paper argues that in addition to the familiar approach using formal contexts, there is now a need in AI to study contexts as social constructs. As a successful example of the latter approach, I draw attention to `interpretation' (in the sense of literary theory), viz. the reconstruction of intended meaning of a literary text that takes into account the context in which the author assumed the reader would place the text. An important contribution here comes from Harris (1988), (...) enumerating the seven crucial dimensions of context: knowledge of reality, knowledge of language, and the authorial, generic, collective, specific, and textual dimensions. Finally, two thought-provoking papers in interpretation, (Barwise 1989) and (Hobbs 1990), are analyzed as useful attempts which also come to grips with the notion of context. (shrink)

This is a review of From Discourse to Logic: Introduction to Model-theoretic Semantics of Natural Language, Formal Logic and Discourse Representation Theory, by Hans Kamp and Uwe Reyle, published by Kluwer Academic Publishers in 1993.

In traditional linguistic accounts of context, one thinks of the immediate features of a speech situation, that is, a situation in which an expression is uttered. Thus, features such as time, location, speaker, hearer and preceding discourse are all parts of context. But context is a wider and more transcendental notion than what these accounts imply. For one thing, context is a relational concept relating social actions and their surroundings, relating social actions, relating individual actors and their surroundings, and relating (...) the set of individual actors and their social actions to their surroundings. (shrink)

While situation theory and situation semantics (Barwise and Perry 1983) provide an appropriate framework for a realistic model-theoretic treatment of natural language, serious thinking on their `computational' aspects has only recently started (Black 1993, Nakashima et al. 1988). Existing proposals mainly o er a Prolog- or Lisp-like programming environment with varying degrees of divergence from the ontology of situation theory. In this paper, we introduce a computational medium (called BABY-SIT) based on situations (T n and Akman 1994a, T n and (...) Akman 1994b). The primary motivation underlying BABY-SIT is to facilitate the development and testing of programs in domains ranging from linguistics to arti cial intelligence in a uni ed framework built upon situation-theoretic constructs. (shrink)

We take em-dash as our sample punctuation mark and examine its usage from a discourse perspective, using sentences from well-known corpora. We particularly comment on how dashes can give hints on information structure, focus, and anaphora. Throughout the paper Discourse Representation Theory is used as a framework. Keywords: Punctuation, Discourse, Discourse Representation Theory, Information Structure..

Following its inception (Barwise and Perry, 1983), situation theory has quickly matured (Cooper et al., 1990; Devlin, 1991) and under the familiarname of situation semantics has been applied to a number of linguistic issues (Barwise, 1987; Barwise, 1989; Barwise and Etchemendy, 1987; Cooper, 1986; Cooper, 1991; Cooper et al., 1990; Fenstad et al., 1987), including quanti cation and anaphora (Gawron and Peters, 1990). In the past, the development of a `mathematical'situation theory has been held back by a lack of availability (...) of appropriate technical tools. But by now, the theory has assembled its mathematical foundations based on intuitions basically coming from set theory and logic (Aczel, 1988; Barwise, 1989; Cooper et al., 1990). With a remarkably original view of information (which is fully adapted by situation theory) (Dretske, 1981), a `logic,' based not on truth but on information, is being developed (Devlin, 1991). This logic will probably be an extension of rst-order logic (Barwise, 1977) rather than being an alternative to it. (shrink)

The merits of set theory as a foundational tool in mathematics stimulate its use in various areas of artificial intelligence, in particular intelligent information systems. In this paper, a study of various nonstandard treatments of set theory from this perspective is offered. Applications of these alternative set theories to information or knowledge management are surveyed.

Punctuation has so far attracted attention within the linguistics community mostly from a syntactic perspective. In this paper, we give a preliminary account of the information-based aspects of punctuation, drawing our points from assorted, naturally occurring sentences. We present our formal models of these sentences and the semantic contributions of punctuation marks. Our formalism is a simpli ed analogue of an extension|due to Nicholas Asher|of Discourse Representation Theory.

Action Languages are formal methods of talking about actions and their effects on fluents. One recent approach in planning is to define the domains of the planning problems using action languages. The aim of this research is to find a plan for a system defined in the action language C by translating it into a causal theory and then finding an equivalent logic program. The planning problem will then be reduced to finding the answer set (stable model) of this logic (...) program. This planner will be added as an extension to the Causal Calculator (CCALC) which is a model checker for the language of the causal theories. (shrink)

This is a brief reply to Herbert A. Simon's fine paper ``Literary Criticism: A Cognitive Approach'', Stanford Humanties Review, Special Supplement (``Bridging the Gap'' Where Cognitive Science Meets Literary Criticism), vol. 4, no. 1, pp. 1-26, Spring 1994.

The author is interested in computational approaches to consciousness. His reason for working in the field of AI is to solve the mind-body problem, that is, to understand how the brain can have experiences. This is an intricate project because it involves elucidation of the relationship between our mentality and its physical foundation. How can a biological/chemical system (the human body) have experiences, beliefs, desires, intentions, and so on? Physicists have good reasons to persuade us that ours is a material (...) world that obeys physical laws. Once we commit ourselves to this view, it sounds quite bewildering to think that there is a place for independently existing minds in such a world. (shrink)

gramming environment, BABY-SIT, which is based on situation theory. We then demonstrate how problems requir-.

and it's just comfortable in here. But what is a belief anyway? How does it acquire the content it has (e.g., that it's chilly in here)? These questions cannot really be answered without clarifying the concept of "a mechanism with a mind". What conditions must be satisfied by a mechanism (say, a computer or a robot) before we can attribute a mind to it? Obviously, the essence of this problem concerns the relation between mental and physical properties. After all, a (...) robot is an inorganic electro-mechanical device, and it is possible to multiply the questions: Can it feel pain? Can it exhibit emotions like fear or anger? Can it develop a taste for Batman movies? Can it decide to spend the next summer in Greenland? Such questions have essentially been the subject matter of the philosophy of mind. A central problem of this discipline -- probably first thought by Descartes in its present form -- is the "mind-body problem". This is the project of elucidating the relationship between our mentality and the physical foundation of our body. How can a biological/physical system such as a human body have beliefs, desires, intentions, and so on? Physicists have persuasive reasons to make us believe that ours is a material world (of particles at the bottommost level) and obeys physical laws. Once we commit ourselves to this worldview, it sounds quite puzzling -- even mysterious -- that there is a place for minds in such a material world. Donald Davidson, probably the greatest living American philosopher, has worked out an ingenious answer to this puzzle. His is a famous but difficult argument and cannot be done justice in this brief outline. Basically, Davidson takes it for granted that the essential properties of matter as described by physicists are the only properties we have. Thus, he subscribes to some form of materialism. However, he thinks that one can be a materialist while also asserting that mental cannot be "reduced" to the physical. Assume that you have complete knowledge in front of you of your brain and any relevant neuro-physiological systems.. (shrink)

Some recent studies in computational linguistics have aimed to take advantage of various cues presented by punctuation marks. This short survey is intended to summarise these research efforts and additionally, to outline a current perspective for the usage and functions of punctuation marks. We conclude by presenting an information-based framework for punctuation, influenced by treatments of several related phenomena in computational linguistics.

In this paper we attempt to develop a problem representation technique which enables the decomposition of a problem into subproblems such that their solution in sequence constitutes a strategy for solving the problem. An important issue here is that the subproblems generated should be easier than the main problem. We propose to represent a set of problem states by a statement which is true for all the members of the set. A statement itself is just a set of atomic statements (...) which are binary predicates on state variables. Then, the statement representing the set of goal states can be partitioned into its subsets each of which becomes a subgoal of the resulting strategy. The techniques involved in partitioning a goal into its subgoals are presented with examples. (shrink)

An efficient algorithm, HALO, is given to compute As computer aided design (CAD) deals with more com- haloed line drawings of wire frame objects. (Haloed..

This is a review of Mind Design II: Philosophy, Psychology, and Artificial Intelligence, edited by John Haugeland, published by MIT Press in 1997.

Founded in 1993, ELEKTRIK: Turkish Journal of Electrical Engineering and Computer Sciences, has gradually become better known and is fast establishing itself as a research oriented publication outlet with high academic standards. In a modest attempt to advance this trend, this special issue of ELEKTRIK brings together five papers exemplifying the state of the art in artificial intelligence (AI). Written by experts, the papers are especially aimed at readers interested in gaining a better appraisal of the applications side of the (...) AI enterprise. In all papers there is a strong emphasis on measuring the benefits of the proposed approaches in experimental contexts. The papers broadly fall into five actively researched, contemporary domains of AI: pattern recognition, genetic algorithms, fuzzy sets, intelligent design, and agents. (shrink)

We o er a preliminary account of the information-based aspects of punctuation marks. We give our initial treatment within the Discourse Representation Theory and its segmented version. We hypothesize that this work will be useful in classifying the informational contributions of punctuation marks and bringing them to bear on the semantic characterization of written discourse.

We focus on how we should define the relevance of information to a context for information processing agents, such as oracles. We build our formalization of relevance upon works in pragmatics which refer to contextual information without giving any explicit representation of context. We use a formalization of context (due to us) in Situation Theory, and demonstrate its power in this task. We also discuss some computational aspects of this formalization.

Serious thinking about the computational aspects of situation theory is just starting. There have been some recent proposals in this direction (viz. PROSIT and ASTL), with varying degrees of divergence from the ontology of the theory. We believe that a programming environment incorporating bona de situation-theoretic constructs is needed and describe our very recent BABY-SIT implementation. A detailed critical account of PROSIT and ASTL is also o ered in order to compare our system with these pioneering and in uential frameworks.

On Crimmins and Perry’s account of propositional attitude ascription (1989), beliefs are concrete cognitive structures—particulars ("things in the head") that belong to an agent and that have a lifetime. They are related to the world and to other cognitive structures and abilities, allowing one to classify the latter by propositional content. Containing ideas and notions as constituents, beliefs are structured entities. The difference between notions and ideas is the difference between an agent’s ways of thinking about individuals vs. properties.