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System Description: Twelf  A MetaLogical Framework for Deductive Systems
 Proceedings of the 16th International Conference on Automated Deduction (CADE16
, 1999
"... . Twelf is a metalogical framework for the specification, implementation, and metatheory of deductive systems from the theory of programming languages and logics. It relies on the LF type theory and the judgmentsastypes methodology for specification [HHP93], a constraint logic programming interp ..."
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Cited by 314 (50 self)
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. Twelf is a metalogical framework for the specification, implementation, and metatheory of deductive systems from the theory of programming languages and logics. It relies on the LF type theory and the judgmentsastypes methodology for specification [HHP93], a constraint logic programming interpreter for implementation [Pfe91], and the metalogic M2 for reasoning about object languages encoded in LF [SP98]. It is a significant extension and complete reimplementation of the Elf system [Pfe94]. Twelf is written in Standard ML and runs under SML of New Jersey and MLWorks on Unix and Window platforms. The current version (1.2) is distributed with a complete manual, example suites, a tutorial in the form of online lecture notes [Pfe], and an Emacs interface. Source and binary distributions are accessible via the Twelf home page http://www.cs.cmu.edu/~twelf. 1 The Twelf System The Twelf system is a tool for experimentation in the theory of programming languages and logics. It supports...
Foundational ProofCarrying Code
, 2001
"... Proofcarrying code is a framework for the mechanical verification of safety properties of machine language programs, but the problem arises of quis custodiat ipsos custodeswho will verify the verifier itself? Foundational proofcarrying code is verification from the smallest possible set of axio ..."
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Cited by 232 (9 self)
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Proofcarrying code is a framework for the mechanical verification of safety properties of machine language programs, but the problem arises of quis custodiat ipsos custodeswho will verify the verifier itself? Foundational proofcarrying code is verification from the smallest possible set of axioms, using the simplest possible verifier and the smallest possible runtime system. I will describe many of the mathematical and engineering problems to be solved in the construction of a foundational proofcarrying code system.
A Linear Logical Framework
, 1996
"... We present the linear type theory LLF as the forAppeared in the proceedings of the Eleventh Annual IEEE Symposium on Logic in Computer Science  LICS'96 (E. Clarke editor), pp. 264275, New Brunswick, NJ, July 2730 1996. mal basis for a conservative extension of the LF logical framework. ..."
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Cited by 215 (44 self)
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We present the linear type theory LLF as the forAppeared in the proceedings of the Eleventh Annual IEEE Symposium on Logic in Computer Science  LICS'96 (E. Clarke editor), pp. 264275, New Brunswick, NJ, July 2730 1996. mal basis for a conservative extension of the LF logical framework. LLF combines the expressive power of dependent types with linear logic to permit the natural and concise representation of a whole new class of deductive systems, namely those dealing with state. As an example we encode a version of MiniML with references including its type system, its operational semantics, and a proof of type preservation. Another example is the encoding of a sequent calculus for classical linear logic and its cut elimination theorem. LLF can also be given an operational interpretation as a logic programming language under which the representations above can be used for type inference, evaluation and cutelimination. 1 Introduction A logical framework is a formal system desig...
An Indexed Model of Recursive Types for Foundational ProofCarrying Code
 ACM Transactions on Programming Languages and Systems
, 2000
"... The proofs of "traditional" proof carrying code (PCC) are typespecialized in the sense that they require axioms about a specific type system. In contrast, the proofs of foundational PCC explicitly define all required types and explicitly prove all the required properties of those types as ..."
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Cited by 136 (13 self)
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The proofs of "traditional" proof carrying code (PCC) are typespecialized in the sense that they require axioms about a specific type system. In contrast, the proofs of foundational PCC explicitly define all required types and explicitly prove all the required properties of those types assuming only a fixed foundation of mathematics such as higherorder logic. Foundational PCC is both more flexible and more secure than typespecialized PCC.
Unification via Explicit Substitutions: The Case of HigherOrder Patterns
 PROCEEDINGS OF JICSLP'96
, 1998
"... In [6] we have proposed a general higherorder unification method using a theory of explicit substitutions and we have proved its completeness. In this paper, we investigate the case of higherorder patterns as introduced by Miller. We show that our general algorithm specializes in a very convenient ..."
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Cited by 56 (14 self)
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In [6] we have proposed a general higherorder unification method using a theory of explicit substitutions and we have proved its completeness. In this paper, we investigate the case of higherorder patterns as introduced by Miller. We show that our general algorithm specializes in a very convenient way to patterns. We also sketch an efficient implementation of the abstract algorithm and its generalization to constraint simplification, which has yielded good experimental results at the core of a higherorder constraint logic programming language.
Efficient resource management for linear logic proof search
 Proceedings of the 5th International Workshop on Extensions of Logic Programming
, 1996
"... The design of linear logic programming languages and theorem provers opens a number of new implementation challenges not present in more traditional logic languages such as Horn clauses (Prolog) and hereditary Harrop formulas (λProlog and Elf). Among these, the problem of efficiently managing the li ..."
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Cited by 54 (11 self)
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The design of linear logic programming languages and theorem provers opens a number of new implementation challenges not present in more traditional logic languages such as Horn clauses (Prolog) and hereditary Harrop formulas (λProlog and Elf). Among these, the problem of efficiently managing the linear context when solving a goal is of crucial importance for the use of these systems in nontrivial applications. This paper studies this problem in the case of Lolli [HM94], though its results have application to other systems. We first give a prooftheoretic presentation of the operational semantics of this language as a resolution calculus. We then present a series of resource management systems designed to eliminate the nondeterminism in the distribution of linear formulas that undermines the efficiency of a direct implementation of this system. 1
Automated Theorem Proving in a Simple MetaLogic for LF
 PROCEEDINGS OF THE 15TH INTERNATIONAL CONFERENCE ON AUTOMATED DEDUCTION (CADE15
, 1998
"... Higherorder representation techniques allow elegant encodings of logics and programming languages in the logical framework LF, but unfortunately they are fundamentally incompatible with induction principles needed to reason about them. In this paper we develop a metalogic M_2 which allows i ..."
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Cited by 35 (16 self)
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Higherorder representation techniques allow elegant encodings of logics and programming languages in the logical framework LF, but unfortunately they are fundamentally incompatible with induction principles needed to reason about them. In this paper we develop a metalogic M_2 which allows inductive reasoning over LF encodings, and describe its implementation in Twelf, a specialpurpose automated theorem prover for properties of logics and programming languages. We have used Twelf to automatically prove a number of nontrivial theorems, including type preservation for MiniML and the deduction theorem for intuitionistic propositional logic.
Model Checking for Infinite State Systems Using Data Abstraction, AssumptionCommitment Style Reasoning and Theorem Proving
, 1995
"... A method combining data abstraction, model checking and theorem proving is presented. It provides a semiautomatic, formal framework for proving arbitrary linear time temporal logic properties of infinite state reactive systems. The paper contains a complete case study to prove safety and liveness o ..."
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Cited by 35 (0 self)
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A method combining data abstraction, model checking and theorem proving is presented. It provides a semiautomatic, formal framework for proving arbitrary linear time temporal logic properties of infinite state reactive systems. The paper contains a complete case study to prove safety and liveness of an implementation of a scheduler for the readers/writers problem which uses unbounded queues and sets. We argue that the proposed framework could be automated to a very large extent making this approach feasible in an industrial environment.
Mode and Termination Checking for HigherOrder Logic Programs
 In Hanne Riis Nielson, editor, Proceedings of the European Symposium on Programming
, 1996
"... . We consider how mode (such as input and output) and termination properties of typed higherorder constraint logic programming languages may be declared and checked effectively. The systems that we present have been validated through an implementation and numerous case studies. 1 Introduction Jus ..."
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Cited by 34 (11 self)
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. We consider how mode (such as input and output) and termination properties of typed higherorder constraint logic programming languages may be declared and checked effectively. The systems that we present have been validated through an implementation and numerous case studies. 1 Introduction Just like other paradigms logic programming benefits tremendously from types. Perhaps most importantly, types allow the early detection of errors when a program is checked against a type specification. With some notable exceptions most type systems proposed for logic programming languages to date (see [18]) are concerned with the declarative semantics of programs, for example, in terms of manysorted, ordersorted, or higherorder logic. Operational properties of logic programs which are vital for their correctness can thus neither be expressed nor checked and errors will remain undetected. In this paper we consider how the declaration and checking of mode (such as input and output) and termina...
A Linear Spine Calculus
 Journal of Logic and Computation
, 2003
"... We present the spine calculus S ##&# as an efficient representation for the linear #calculus # ##&# which includes unrestricted functions (#), linear functions (#), additive pairing (&), and additive unit (#). S ##&# enhances the representation of Church's simply typed # ..."
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Cited by 33 (6 self)
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We present the spine calculus S ##&# as an efficient representation for the linear #calculus # ##&# which includes unrestricted functions (#), linear functions (#), additive pairing (&), and additive unit (#). S ##&# enhances the representation of Church's simply typed #calculus by enforcing extensionality and by incorporating linear constructs. This approach permits procedures such as unification to retain the efficient head access that characterizes firstorder term languages without the overhead of performing #conversions at run time. Applications lie in proof search, logic programming, and logical frameworks based on linear type theories. It is also related to foundational work on term assignment calculi for presentations of the sequent calculus. We define the spine calculus, give translations of # ##&# into S ##&# and viceversa, prove their soundness and completeness with respect to typing and reductions, and show that the typable fragment of the spine calculus is strongly normalizing and admits unique canonical, i.e. ##normal, forms.