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Nominal System T
, 2010
"... This paper introduces a new recursion principle for inductive data modulo ..."
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This paper introduces a new recursion principle for inductive data modulo
Structural Recursion with Locally Scoped Names
"... This paper introduces a new recursion principle for inductively defined data modulo α-equivalence of bound names that makes use of Odersky-style local names when recursing over bound names. It is formulated in simply typed λ-calculus extended with names that can be restricted to a lexical scope, tes ..."
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This paper introduces a new recursion principle for inductively defined data modulo α-equivalence of bound names that makes use of Odersky-style local names when recursing over bound names. It is formulated in simply typed λ-calculus extended with names that can be restricted to a lexical scope, tested for equality, explicitly swapped and abstracted. The new recursion principle is motivated by the nominal sets notion of “α-structural recursion”, whose use of names and associated freshness side-conditions in recursive definitions formalizes common practice with binders. The new calculus has a simple interpretation in nominal sets equipped with name restriction operations. It is shown to adequately represent α-structural recursion while avoiding the need to verify freshness side-conditions in definitions and computations. The paper is a revised and expanded version of (Pitts, 2010). 1
Dependently Typed Programming with Domain-Specific Logics
, 2011
"... sponsoring institution, the U.S. government or any other entity. ..."
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sponsoring institution, the U.S. government or any other entity.
Substructural Logical Specifications
, 2012
"... Any opinions, findings, conclusions or recommendations expressed in this publication are those of the author and A logical framework and its implementation should serve as a flexible tool for specifying, simulating, and reasoning about formal systems. When the formal systems we are interested in exh ..."
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Any opinions, findings, conclusions or recommendations expressed in this publication are those of the author and A logical framework and its implementation should serve as a flexible tool for specifying, simulating, and reasoning about formal systems. When the formal systems we are interested in exhibit state and concurrency, however, existing logical frameworks fall short of this goal. Logical frameworks based on a rewriting interpretation of substructural logics, ordered and linear logic in particular, can help. To this end, this dissertation introduces and demonstrates four methodologies for developing and using substructural logical frameworks for specifying and reasoning about stateful and concurrent systems. Structural focalization is a synthesis of ideas from Andreoli’s focused sequent calculi and Watkins’s hereditary substitution. We can use structural focalization to take a logic and define a restricted form of derivations, the focused derivations, that form the basis of a logical framework. We apply this methodology to define SLS, a logical framework for substructural logical specifications, as a fragment of ordered
The Representational Adequacy of HYBRID
"... The Hybrid system (Ambler et al., 2002b), implemented within Isabelle/HOL, allows object logics to be represented using higher order abstract syntax (HOAS), and reasoned about using tactical theorem proving in general and principles of (co)induction in particular. The form of HOAS provided by Hybrid ..."
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The Hybrid system (Ambler et al., 2002b), implemented within Isabelle/HOL, allows object logics to be represented using higher order abstract syntax (HOAS), and reasoned about using tactical theorem proving in general and principles of (co)induction in particular. The form of HOAS provided by Hybrid is essentially a lambda calculus with constants. Of fundamental interest is the form of the lambda abstractions provided by Hybrid. The user has the convenience of writing lambda abstractions using names for the binding variables. However each abstraction is actually a definition of a de Bruijn expression, and Hybrid can unwind the user’s abstractions (written with names) to machine friendly de Bruijn expressions (without names). In this sense the formal system contains a hybrid of named and nameless bound variable notation. In this paper, we present a formal theory in a logical framework which can be viewed as a model of core Hybrid, and state and prove that the model is representationally adequate for HOAS. In particular, it is the canonical translation function from λ-expressions to Hybrid that witnesses adequacy. We also prove two results that characterise how Hybrid represents certain classes of λ-expressions. The Hybrid system contains a number of different syntactic classes of expression, and associated abstraction mechanisms. Hence this paper also aims to provide a self-contained theoretical introduction to both the syntax and key ideas of the system; background in automated theorem proving is not essential, although this paper will be of considerable interest to those who wish to work with Hybrid in Isabelle/HOL.
Dependent Types for Nominal Terms with Atom Substitutions
"... Abstract Nominal terms are an extended first-order language for specifying and verifying properties of syntax with binding. Founded upon the semantics of nominal sets, the success of nominal terms with regard to systems of equational reasoning is already well established. This work first extends th ..."
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Abstract Nominal terms are an extended first-order language for specifying and verifying properties of syntax with binding. Founded upon the semantics of nominal sets, the success of nominal terms with regard to systems of equational reasoning is already well established. This work first extends the untyped language of nominal terms with a notion of non-capturing atom substitution for object-level names and then proposes a dependent type system for this extended language. Both these contributions are intended to serve as a prelude to a future nominal logical framework based upon nominal equational reasoning and thus an extended example is given to demonstrate that this system is capable of encoding various other formal systems of interest.
Nominal Coalgebraic Data Types . . .
"... We investigate final coalgebras in nominal sets. This allows us to define types of infinite data with binding for which all constructions automatically respect alpha equivalence. We give applications to the infinitary lambda calculus. ..."
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We investigate final coalgebras in nominal sets. This allows us to define types of infinite data with binding for which all constructions automatically respect alpha equivalence. We give applications to the infinitary lambda calculus.
Dependent Types for a Nominal Logical Framework
, 2012
"... We present a logical framework based on the nominal approach to representing syntax with binders. First we extend nominal terms, which have a built-in name-abstraction operator and a first-order notion of substitution for variables, with a capture-avoiding substitution operator for names. We then bu ..."
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We present a logical framework based on the nominal approach to representing syntax with binders. First we extend nominal terms, which have a built-in name-abstraction operator and a first-order notion of substitution for variables, with a capture-avoiding substitution operator for names. We then build a dependent type system for this extended syntax
