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103
A Methodology for Using a Default and Abductive Reasoning System
, 1994
"... This paper investigates two different activities that involve making assumptions: predicting what one expects to be true and explaining observations. In a companion paper, an architecture for both prediction and explanation is proposed and an implementation is outlined. In this paper, we show how su ..."
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Cited by 58 (10 self)
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This paper investigates two different activities that involve making assumptions: predicting what one expects to be true and explaining observations. In a companion paper, an architecture for both prediction and explanation is proposed and an implementation is outlined. In this paper, we show how such a hypothetical reasoning system can be used to solve recognition, diagnostic and prediction problems. As part of this is the assumption that the default reasoner must be "programmed" to get the right answer and it is not just a matter of "stating what is true" and hoping the system will magically find the right answer. A number of distinctions have been found in practice to be important: between predicting whether something is expected to be true versus explaining why it is true; and between conventional defaults (assumptions as a communication convention), normality defaults (assumed for expediency) and conjectures (assumed only if there is evidence). The effects of these distinctions on...
Semantic Issues in Deductive Databases and Logic Programs
 Formal Techniques in Artificial Intelligence
, 1990
"... this paper. In particular, the paper reports on a very significant progress made recently in this area. It also presents some results which have not yet appeared in print. The paper is organized as follows. In the next two sections we define deductive databases and logic programs. Subsequently, in ..."
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Cited by 54 (12 self)
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this paper. In particular, the paper reports on a very significant progress made recently in this area. It also presents some results which have not yet appeared in print. The paper is organized as follows. In the next two sections we define deductive databases and logic programs. Subsequently, in Sections 4 and 5, we discuss model theory and fixed points, which play a crucial role in the definition of semantics. Section 6 is the main section of the paper and is entirely devoted to a systematic exposition and comparison of various proposed semantics. In Section 7 we discuss the relationship between declarative semantics of deductive databases and logic programs and nonmonotonic reasoning. Section 8 contains concluding remarks. 2 Deductive Databases
Representation and reasoning with attributive descriptions
 SORTS AND TYPES IN ARTIFICIAL INTELLIGENCE
, 1990
"... This paper surveys terminological representation languages and featurebased unification grammars pointing out the similarities and differences between these two families of attributive description formalisms. Emphasis is given to the logical foundations of these formalisms. ..."
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Cited by 49 (12 self)
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This paper surveys terminological representation languages and featurebased unification grammars pointing out the similarities and differences between these two families of attributive description formalisms. Emphasis is given to the logical foundations of these formalisms.
Integrating computer algebra into proof planning
 Journal of Automated Reasoning
, 1998
"... Abstract. Mechanised reasoning systems and computer algebra systems have different objectives. Their integration is highly desirable, since formal proofs often involve both of the two di erent tasks, proving and calculating. Even more importantly, proof and computation are often interwoven and not e ..."
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Cited by 41 (26 self)
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Abstract. Mechanised reasoning systems and computer algebra systems have different objectives. Their integration is highly desirable, since formal proofs often involve both of the two di erent tasks, proving and calculating. Even more importantly, proof and computation are often interwoven and not easily separable. In this contribution we advocate an integration of computer algebra into mechanised reasoning systems at the proof plan level. This approach allows to view the computer algebra algorithms as methods, that is, declarative representations of the problem solving knowledge speci c to a certain mathematical domain. Automation can be achieved in many cases bysearching for a hierarchic proof plan at the methodlevel using suitable domainspeci c control knowledge about the mathematical algorithms. In other words, the uniform framework of proof planning allows to solve a large class of problems that are not automatically solvable by separate systems. Our approach also gives an answer to the correctness problems inherent insuch an integration. We advocate an approach where the computer algebra system produces highlevel protocol information that can be processed by aninterface to derive proof plans. Such a proof plan in turn can be expanded to proofs at di erent levels of abstraction, so the approach iswellsuited for producing a highlevel verbalised explication as well as for a lowlevel machine checkable calculuslevel proof. We present an implementation of our ideas and exemplify them using an automatically solved example. Changes in the criterion of `rigour of the proof ' engender major revolutions in mathematics.
Derivation of Data Intensive Algorithms by Formal Transformation: The SchorrWaite Graph Marking Algorithm
, 1996
"... In this paper we consider a particular class of algorithms which present certain difficulties to formal verification. These are algorithms which use a single data structure for two or more purposes, which combine program control information with other data structures or which are developed as a comb ..."
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Cited by 36 (25 self)
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In this paper we consider a particular class of algorithms which present certain difficulties to formal verification. These are algorithms which use a single data structure for two or more purposes, which combine program control information with other data structures or which are developed as a combination of a basic idea with an implementation technique. Our approach is based on applying proven semanticspreserving transformation rules in a wide spectrum language. Starting with a set theoretical specification of "reachability" we are able to derive iterative and recursive graph marking algorithms using the "pointer switching" idea of Schorr and Waite. There have been several proofs of correctness of the SchorrWaite algorithm, and a small number of transformational developments of the algorithm. The great advantage of our approach is that we can derive the algorithm from its specification using only generalpurpose transformational rules: without the need for complicated induction arg...
Continuation Semantics for Prolog with Cut
, 1989
"... We present a denotational continuation semantics for Prolog with cut. First a uniform language B is studied, which captures the control flow aspects of Prolog. The denotational semantics for B is proven equivalent to a transition system based operational semantics. The congruence proof relies on the ..."
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Cited by 34 (5 self)
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We present a denotational continuation semantics for Prolog with cut. First a uniform language B is studied, which captures the control flow aspects of Prolog. The denotational semantics for B is proven equivalent to a transition system based operational semantics. The congruence proof relies on the representation of the operational semantics as a chain of approximations and on a convenient induction principle. Finally, we interpret the abstract language B such that we obtain equivalent denotational and operational models for Prolog itself. Section 1 Introduction In the nice textbook of Lloyd [Ll] the cut, available in all Prologsystems, is described as a controversial control facility. The cut, added to the Horn clause logic for efficiency reasons, affects the completeness of the refutation procedure. Therefore the standard declarative semantics using Herbrand models does not adequately capture the computational aspects of the Prologlanguage. In the present paper we study the Prolog...
Logic programming for robot control
 Proc. 14th International Joint Conf. on Artificial Intelligence (IJCAI95
, 1995
"... This paper proposes logic programs as a specification for robot control. These provide a formal specification of what an agent should do depending on what it senses, and its previous sensory inputs and actions. We show how to axiomatise reactive agents, events as an interface between continuous and ..."
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Cited by 32 (7 self)
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This paper proposes logic programs as a specification for robot control. These provide a formal specification of what an agent should do depending on what it senses, and its previous sensory inputs and actions. We show how to axiomatise reactive agents, events as an interface between continuous and discrete time, and persistence, as well as axiomatising integration and differentiation over time (in terms of the limit of sums and differences). This specification need not be evaluated as a Prolog program; we use can the fact that it will be evaluated in time to get a more efficient agent. We give a detailed example of a nonholonomic maze travelling robot, where we use the same language to model both the agent and the environment. One of the main motivations for this work is that there is a clean interface between the logic programs here and the model of uncertainty embedded in probabilistic Horn abduction. This is one step towards building a decisiontheoretic planning system where the output of the planner is a plan suitable for actually controlling a robot. 1
Verification of Logic Programs with Delay Declarations
 Proceedings of the Fourth International Conference on Algebraic Methodology and Software Technology, (AMAST'95), Lecture Notes in Computer Science
, 1995
"... . Logic programs augmented with delay declarations form a higly expressive programming language in which dynamic networks of processes that communicate asynchronously by means of multiparty channels can be easily created. In this paper we study correctness these programs. In particular, we propose p ..."
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Cited by 32 (1 self)
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. Logic programs augmented with delay declarations form a higly expressive programming language in which dynamic networks of processes that communicate asynchronously by means of multiparty channels can be easily created. In this paper we study correctness these programs. In particular, we propose proof methods allowing us to deal with occur check freedom, absence of deadlock, absence of errors in presence of arithmetic relations, and termination. These methods turn out to be simple modifications of the corresponding methods dealing with Prolog programs. This allows us to derive correct delay declarations by analyzing Prolog programs. Finally, we point out difficulties concerning proofs of termination. Notes. The research of the first author was partly supported by the ESPRIT Basic Research Action 6810 (Compulog 2). This paper will appear as an invited lecture in: Proc. of the Fourth International Conference on Algebraic Methodology and Software Technology, (AMAST'95). 1 Introduction ...
Compiling A Default Reasoning System into Prolog
 New Generation Computing
, 1990
"... Artificial intelligence researchers have been designing representation systems for default and abductive reasoning. Logic Programming researchers have been working on techniques to improve the efficiency of Horn Clause deduction systems. This paper describes how one such default and abductive reason ..."
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Cited by 30 (4 self)
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Artificial intelligence researchers have been designing representation systems for default and abductive reasoning. Logic Programming researchers have been working on techniques to improve the efficiency of Horn Clause deduction systems. This paper describes how one such default and abductive reasoning system (namely Theorist) can be translated into Horn clauses (with negation as failure), so that we can use the clarity of abductive reasoning systems and the efficiency of Horn clause deduction systems. We thus show how advances in expressive power that artificial intelligence workers are working on can directly utilise advances in efficiency that logic programming researchers are working on. Actual code from a running system is given. 1 Introduction Many people in Artificial Intelligence have been working on default reasoning and abductive diagnosis systems [35, 20, 4, 29]. The systems implemented so far (eg., [1, 16, 12, 34, 32]) are only prototypes or have been developed in A Theo...
Sketching Concurrent Data Structures
, 2008
"... We describe PSKETCH, a program synthesizer that helps programmers implement concurrent data structures. The system is based on the concept of sketching, a form of synthesis that allows programmers to express their insight about an implementation as a partial program: a sketch. The synthesizer automa ..."
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Cited by 25 (3 self)
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We describe PSKETCH, a program synthesizer that helps programmers implement concurrent data structures. The system is based on the concept of sketching, a form of synthesis that allows programmers to express their insight about an implementation as a partial program: a sketch. The synthesizer automatically completes the sketch to produce an implementation that matches a given correctness criteria. PSKETCH is based on a new counterexampleguided inductive synthesis algorithm (CEGIS) that generalizes the original sketch synthesis algorithm from [20] to cope efficiently with concurrent programs. The new algorithm produces a correct implementation by iteratively generating candidate implementations, running them through a verifier, and if they fail, learning from the counterexample traces to produce a better candidate; converging to a solution in a handful of iterations. PSKETCH also extends SKETCH with higherlevel sketching constructs that allow the programmer to express her insight as a “soup ” of ingredients from which complicated code fragments must be assembled. Such sketches can be viewed as syntactic descriptions of huge spaces of candidate programs (over 10 8 candidates for some sketches we resolved). We have used the PSKETCH system to implement several classes of concurrent data structures, including lockfree queues and concurrent sets with finegrained locking. We have also sketched some other concurrent objects including a sensereversing barrier and a protocol for the dining philosophers problem; all these sketches resolved in under an hour.