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A module calculus for Pure Type Systems
, 1996
"... Several proofassistants rely on the very formal basis of Pure Type Systems. However, some practical issues raised by the development of large proofs lead to add other features to actual implementations for handling namespace management, for developing reusable proof libraries and for separate verif ..."
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Several proofassistants rely on the very formal basis of Pure Type Systems. However, some practical issues raised by the development of large proofs lead to add other features to actual implementations for handling namespace management, for developing reusable proof libraries and for separate verification of distincts parts of large proofs. Unfortunately, few theoretical basis are given for these features. In this paper we propose an extension of Pure Type Systems with a module calculus adapted from SMLlike module systems for programming languages. Our module calculus gives a theoretical framework addressing the need for these features. We show that our module extension is conservative, and that type inference in the module extension of a given PTS is decidable under some hypotheses over the considered PTS.
Dependently Typed Records for Representing Mathematical Structure
 Theorem Proving in Higher Order Logics, TPHOLs 2000
, 2000
"... this paper appears in Theorem Proving in Higher Order Logics, TPHOLs 2000, c ..."
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this paper appears in Theorem Proving in Higher Order Logics, TPHOLs 2000, c
Higman's Lemma in Type Theory
 PROCEEDINGS OF THE 1996 WORKSHOP ON TYPES FOR PROOFS AND PROGRAMS
, 1997
"... This thesis is about exploring the possibilities of a limited version of MartinLöf's type theory. This exploration consists both of metatheoretical considerations and of the actual use of that version of type theory to prove Higman's lemma. The thesis is organized in two papers, one in which type t ..."
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This thesis is about exploring the possibilities of a limited version of MartinLöf's type theory. This exploration consists both of metatheoretical considerations and of the actual use of that version of type theory to prove Higman's lemma. The thesis is organized in two papers, one in which type theory itself is studied and one in which it is used to prove Higman's lemma. In the first paper, A Lambda Calculus Model of MartinLöf's Theory of Types with Explicit Substitution, we present the formal calculus in complete detail. It consists of MartinLof's logical framework with explicit substitution extended with some inductively defined sets, also given in complete detail. These inductively defined sets are precisely those we need in the second paper of this thesis for the formal proof of Higman's lemma. The limitations of the formalism come from the fact that we do not introduce universes. It is known that for other versions of type theory, the absence of universes implies the impossib...
Dependent Record Types, Subtyping and Proof Reutilization
"... . We present an example of formalization of systems of algebras using an extension of MartinLof's theory of types with record types and subtyping. This extension has been presented in [5]. In this paper we intend to illustrate all the features of the extended theory that we consider relevant for th ..."
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. We present an example of formalization of systems of algebras using an extension of MartinLof's theory of types with record types and subtyping. This extension has been presented in [5]. In this paper we intend to illustrate all the features of the extended theory that we consider relevant for the task of formalizing algebraic constructions. We also provide code of the formalization as accepted by a type checker that has been implemented. 1. Introduction We shall use an extension of MartinLof's theory of logical types [14] with dependent record types and subtyping as the formal language in which constructions concerning systems of algebras are going to be represented. The original formulation of MartinLof's theory of types, from now on referred to as the logical framework, has been presented in [15, 7]. The system of types that this calculus embodies are the type Set (the type of inductively defined sets), dependent function types and for each set A, the type of the elements of A...
An Interpretation of the Fan Theorem in Type Theory
 in International Workshop on Types for Proofs and Programs 1998, TYPES '98 Selected Papers, LNCS
, 1998
"... This article presents a formulation of the fan theorem in MartinLöf's type theory. Starting from one of the standard versions of the fan theorem we gradually introduce reformulations leading to a final version which is easy to interpret in type theory. Finally we describe a formal proof of that fin ..."
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This article presents a formulation of the fan theorem in MartinLöf's type theory. Starting from one of the standard versions of the fan theorem we gradually introduce reformulations leading to a final version which is easy to interpret in type theory. Finally we describe a formal proof of that final version of the fan theorem.
Proof Reutilization in MartinLöf's Logical Framework Extended with Record Types and Subtyping
, 2000
"... The extension of MartinLöf's theory of types with record types and subtyping has elsewhere been presented. We give a concise description of that theory and motivate its use for the formalization of systems of algebras. We also give a short account of a proof checker that has been implemented on mac ..."
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The extension of MartinLöf's theory of types with record types and subtyping has elsewhere been presented. We give a concise description of that theory and motivate its use for the formalization of systems of algebras. We also give a short account of a proof checker that has been implemented on machine. The logical heart of the checker is constituted by the procedures for the mechanical verification of the forms of judgement of a particular formulation of the extension. The case study that we put forward in this work has been developed and mechanically verified using the implemented system. We illustrate all the features of the extended theory that we consider relevant for the task of formalizing algebraic constructions.
A lambda calculus model of MartinLöf's theory of types with explicit substitution
 In this thesis
, 1997
"... This paper presents a proofirrelevant model of MartinLof's theory of types with explicit substitution; that is, a model in the style of [Smi88], in which types are interpreted as truth values and objects (or proofs) are irrelevant. The fundamental difference here is the need to cope with a formal ..."
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This paper presents a proofirrelevant model of MartinLof's theory of types with explicit substitution; that is, a model in the style of [Smi88], in which types are interpreted as truth values and objects (or proofs) are irrelevant. The fundamental difference here is the need to cope with a formal system which in addition to types has sets and substitutions. This difference leads us to a whole reformulation of the model which consists in defining an interpretation in terms of the untyped lambda calculus. From this interpretation the proofirrelevant model is obtained as a particular instance. Finally, the paper outlines the definition of a realizability model which is also obtained as a particular instance. Keywords: type theory, explicit substitution, models of type theory, proofirrelevant model, realizability model. Contents 1 Introduction 1 2 Type theory 2 2.1 Syntax : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 3 3 A lambda calculus model 8 3.1 Semantic...