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Integrating decision procedures into heuristic theorem provers: A case study of linear arithmetic
 Machine Intelligence
, 1988
"... We discuss the problem of incorporating into a heuristic theorem prover a decision procedure for a fragment of the logic. An obvious goal when incorporating such a procedure is to reduce the search space explored by the heuristic component of the system, as would be achieved by eliminating from the ..."
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Cited by 107 (9 self)
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We discuss the problem of incorporating into a heuristic theorem prover a decision procedure for a fragment of the logic. An obvious goal when incorporating such a procedure is to reduce the search space explored by the heuristic component of the system, as would be achieved by eliminating from the system’s data base some explicitly stated axioms. For example, if a decision procedure for linear inequalities is added, one would hope to eliminate the explicit consideration of the transitivity axioms. However, the decision procedure must then be used in all the ways the eliminated axioms might have been. The difficulty of achieving this degree of integration is more dependent upon the complexity of the heuristic component than upon that of the decision procedure. The view of the decision procedure as a "black box " is frequently destroyed by the need pass large amounts of search strategic information back and forth between the two components. Finally, the efficiency of the decision procedure may be virtually irrelevant; the efficiency of the final system may depend most heavily on how easy it is to communicate between the two components. This paper is a case study of how we integrated a linear arithmetic procedure into a heuristic theorem prover. By linear arithmetic here we mean the decidable subset of number theory dealing with universally quantified formulas composed of the logical connectives, the identity relation, the Peano "less than " relation, the Peano addition and subtraction functions, Peano constants,
The Semantics of Reflected Proof
 IN PROC. OF FIFTH SYMP. ON LOGIC IN COMP. SCI
, 1990
"... We begin to lay the foundations for reasoning about proofs whose steps include both invocations of programs to build subproofs (tactics) and references to representations of proofs themselves (reflected proofs). The main result is the definition of a single type of proof which can mention itself, ..."
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Cited by 88 (11 self)
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We begin to lay the foundations for reasoning about proofs whose steps include both invocations of programs to build subproofs (tactics) and references to representations of proofs themselves (reflected proofs). The main result is the definition of a single type of proof which can mention itself, using a new technique which finds a fixed point of a mapping between metalanguage and object language. This single type contrasts with hierarchies of types used in other approaches to accomplish the same classification. We show that these proofs are valid, and that every proof can be reduced to a proof involving only primitive inference rules. We also show how to extend the results to proofs from which programs (such as tactics) can be derived, and to proofs that can refer to a library of definitions and previously proven theorems. We believe that the mechanism of reflection is fundamental in building proof development systems, and we illustrate its power with applications to automating reasoning and describing modes of computation.
Reflection and Strategies in Rewriting Logic
, 1996
"... After giving general metalogical axioms characterizing reflection in general logics in terms of the notion of a universal theory , this paper specifies a finitely presented universal theory for rewriting logic and gives a detailed proof of the claim made in [6] that rewriting logic is reflective. Th ..."
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Cited by 61 (27 self)
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After giving general metalogical axioms characterizing reflection in general logics in terms of the notion of a universal theory , this paper specifies a finitely presented universal theory for rewriting logic and gives a detailed proof of the claim made in [6] that rewriting logic is reflective. The paper also gives general axioms for the notion of a strategy language internal to a given logic. Exploiting the fact that rewriting logic is reflexive, a general method for defining internal strategy languages for it and proving their correctness is proposed and is illustrated with an example. The Maude language has been used as an experimental vehicle for the exploration of these techniques. They seem quite promising for applications such as metaprogramming and module composition, logical framework representations, development of formal programming and proving environments, supercompilation, and formal verification of strategies. 1 Introduction Reflection is a very desirable property of ...
Mechanizing Programming Logics in Higher Order Logic
 in Current Trends in Hardware Verification and Automated Theorem Proving, ed. P.A. Subrahmanyam and Graham Birtwistle
, 1989
"... Formal reasoning about computer programs can be based directly on the semantics of the programming language, or done in a special purpose logic like Hoare logic. The advantage of the first approach is that it guarantees that the formal reasoning applies to the language being used (it is well known, ..."
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Cited by 59 (3 self)
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Formal reasoning about computer programs can be based directly on the semantics of the programming language, or done in a special purpose logic like Hoare logic. The advantage of the first approach is that it guarantees that the formal reasoning applies to the language being used (it is well known, for example, that Hoare’s assignment axiom fails to hold for most programming languages). The advantage of the second approach is that the proofs can be more direct and natural. In this paper, an attempt to get the advantages of both approaches is described. The rules of Hoare logic are mechanically derived from the semantics of a simple imperative programming language (using the HOL system). These rules form the basis for a simple program verifier in which verification conditions are generated by LCFstyle tactics whose validations use the derived Hoare rules. Because Hoare logic is derived, rather than postulated, it is straightforward to mix semantic and axiomatic reasoning. It is also straightforward to combine the constructs of Hoare logic with other applicationspecific notations. This is briefly illustrated for various logical constructs, including termination statements, VDMstyle ‘relational’ correctness specifications, weakest precondition statements and dynamic logic formulae. The theory underlying the work presented here is well known. Our contribution is to propose a way of mechanizing this theory in a way that makes certain practical details work out smoothly.
ACL2: An Industrial Strength Version of Nqthm
, 1996
"... ACL2 is a reimplemented extended version of Boyer and Moore's Nqthm and Kaufmann's PcNqthm, intended for large scale verification projects. However, the logic supported by ACL2 is compatible with the applicative subset of Common Lisp. The decision to use an "industrial strength" programming languag ..."
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Cited by 58 (5 self)
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ACL2 is a reimplemented extended version of Boyer and Moore's Nqthm and Kaufmann's PcNqthm, intended for large scale verification projects. However, the logic supported by ACL2 is compatible with the applicative subset of Common Lisp. The decision to use an "industrial strength" programming language as the foundation of the mathematical logic is crucial to our advocacy of ACL2 in the application of formal methods to large systems. However, one of the key reasons Nqthm has been so successful, we believe, is its insistence that functions be total. Common Lisp functions are not total and this is one of the reasons Common Lisp is so efficient. This paper explains how we scaled up Nqthm's logic to Common Lisp, preserving the use of total functions within the logic but achieving Common Lisp execution speeds. 1 History ACL2 is a direct descendent of the BoyerMoore system, Nqthm [8, 12], and its interactive enhancement, PcNqthm [21, 22, 23]. See [7, 25] for introductions to the two ancestr...
Metatheory and Reflection in Theorem Proving: A Survey and Critique
, 1995
"... One way to ensure correctness of the inference performed by computer theorem provers is to force all proofs to be done step by step in a simple, more or less traditional, deductive system. Using techniques pioneered in Edinburgh LCF, this can be made palatable. However, some believe such an appro ..."
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Cited by 53 (2 self)
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One way to ensure correctness of the inference performed by computer theorem provers is to force all proofs to be done step by step in a simple, more or less traditional, deductive system. Using techniques pioneered in Edinburgh LCF, this can be made palatable. However, some believe such an approach will never be efficient enough for large, complex proofs. One alternative, commonly called reflection, is to analyze proofs using a second layer of logic, a metalogic, and so justify abbreviating or simplifying proofs, making the kinds of shortcuts humans often do or appealing to specialized decision algorithms. In this paper we contrast the fullyexpansive LCF approach with the use of reflection. We put forward arguments to suggest that the inadequacy of the LCF approach has not been adequately demonstrated, and neither has the practical utility of reflection (notwithstanding its undoubted intellectual interest). The LCF system with which we are most concerned is the HOL proof ...
Using Reflection to Build Efficient and Certified Decision Procedures
 TACS'97. SpringerVerlag LNCS 1281
, 1997
"... In this paper we explain how computational reflection can help build efficient certified decision procedure in reduction systems. We have developped a decision procedure on abelian rings in the Coq system but the approach we describe applies to all reduction systems that allow the definition of c ..."
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Cited by 46 (0 self)
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In this paper we explain how computational reflection can help build efficient certified decision procedure in reduction systems. We have developped a decision procedure on abelian rings in the Coq system but the approach we describe applies to all reduction systems that allow the definition of concrete types (or datatypes). We show that computational reflection is more efficient than an LCFlike approach to implement decision procedures in a reduction system. We discuss the concept of total reflection, which we have investigated in Coq using two facts: the extraction process available in Coq and the fact that the implementation language of the Coq system can be considered as a sublanguage of Coq. Total reflection is not yet implemented in Coq but we can test its performance as the extraction process is effective. Both reflection and total reflection are conservative extensions of the reduction system in which they are used. We also discuss performance and related approaches....
Design Goals for ACL2
, 1994
"... ACL2 is a theorem proving system under development at Computational Logic, Inc., by the authors of the BoyerMoore system, Nqthm, and its interactive enhancement, PcNqthm, based on our perceptions of some of the inadequacies of Nqthm when used in largescale verification projects. Foremost among th ..."
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Cited by 36 (5 self)
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ACL2 is a theorem proving system under development at Computational Logic, Inc., by the authors of the BoyerMoore system, Nqthm, and its interactive enhancement, PcNqthm, based on our perceptions of some of the inadequacies of Nqthm when used in largescale verification projects. Foremost among those inadequacies is the fact that Nqthm's logic is an inefficient programming language. We now recognize that the efficiency of the logic as a programming language is of great importance because the models of microprocessors, operating systems, and languages typically constructed in verification projects must be executed to corroborate them against the realities they model. Simulation of such large scale systems stresses the logic in ways not imagined when Nqthm was designed. In addition, Nqthm does not adequately support certain proof techniques, nor does it encourage the reuse of previously developed libraries or the collaboration of semiautonomous workers on different parts of a verifica...