We give a detailed, informal proof of the Church-Rosser property for the untyped lambda-calculus and show its representation in LF. The proof is due to Tait and Martin-Löf and is based on the notion of parallel reduction. The representation employs higher-order abstract syntax and the judgments-as-types principle and takes advantage of term reconstruction as it is provided in the Elf implementation of LF. Proofs of meta-theorems are represented as higher-level judgments which relate sequences of reductions and conversions.

. We exhibit a methodology for formulating and verifying metatheorems about deductive systems in the Elf language, an implementation of the LF Logical Framework with an operational semantics in the spirit of logic programming. It is based on the mechanical verification of properties of transformations between deductions, which relies on type reconstruction and schema-checking. The latter is justified by induction principles for closed LF objects, which can be constructed over a given signature. We illustrate our technique through several examples, the most extensive of which is an interpretation of classical logic in minimal logic through a continuation-passing-style transformation on proofs. 1 Introduction Formal deductive systems have become an important tool in computer science. They are used to specify logics, type systems, operational semantics and other aspects of languages. The role of such specifications is three-fold. Firstly, inference rules serve as a high-level notation w...

. We consider the problem of analyzing and proving correct simple closure conversion strategies for a higher-order functional language. We specify the conversions as deductive systems, making use of annotated types to provide constraints which guide the construction of the closures. We exploit the ability of deductive systems to specify concisely complex relationships between source terms and closure-converted terms. The resulting specifications and proofs are relatively clear and straightforward. The use of deductive systems is central to our work as we can subsequently encode these systems in the LF type theory and then code them in the Elf programming language. The correctness proofs can also be coded in this language, providing machine-checked versions of these proofs. 1 Introduction Closure conversion is the process of transforming functions containing free variables into a closures, a representation of a function that consists of a piece of code for the function and a record con...