Proceedings of Sixth International Workshop on Unification

Swiss National Science Foundation; Austrian Federal Ministry of Science and Research; Deutsche Forschungsgemeinschaft (SFB 314); Christ Church, Oxford; Oxford University Computing Laborator

A Decision Algorithm for Linear Isomorphism of Types with Complexity Cn(log2(n))

It is known that ordinary isomorphisms (associativity and commutativityof "times", isomorphisms for "times" unit and currying)provide a complete axiomatisation for linear isomorphism of types.One of the reasons to consider linear isomorphism of types instead ofordinary isomorphism was that better complexity could be expected.Meanwhile, no upper bounds reasonably close to linear were obtained.We describe an algorithm deciding if two types are linearly isomorphicwith complexity Cn(log2(n))

Type indexing in OCaml for function search in a large ecosystem

International audienceWhen it comes to finding functions in libraries, in whichever language, programmers struggle with the need for efficient tools able to retrieve all relevant functions in a reasonable time. For the OCaml language, dowsindex was developed to offer a solution to this problem, via the notion of isomorphisms of types. It relies on the construction of an Index to precompute information on the libraries and thus facilitate the search algorithm. We aim to improve its performances by proposing a new data structure representing the matching relation between types, along with a new heuristic to optimize the type search

Isomorphisms of types in the presence of higher-order references

We investigate the problem of type isomorphisms in a programming language with higher-order references. We first recall the game-theoretic model of higher-order references by Abramsky, Honda and McCusker. Solving an open problem by Laurent, we show that two finitely branching arenas are isomorphic if and only if they are geometrically the same, up to renaming of moves (Laurent's forest isomorphism). We deduce from this an equational theory characterizing isomorphisms of types in a finitary language with higher order references. We show however that Laurent's conjecture does not hold on infinitely branching arenas, yielding a non-trivial type isomorphism in the extension of this language with natural numbers.Comment: Twenty-Sixth Annual IEEE Symposium on Logic In Computer Science (LICS 2011), Toronto : Canada (2011

A theory of contracts for web services

<p>Contracts are behavioural descriptions of Web services. We devise a theory of contracts that formalises the compatibility of a client to a service, and the safe replacement of a service with another service. The use of contracts statically ensures the successful completion of every possible interaction between compatible clients and services.</p> <p>The technical device that underlies the theory is the definition of filters, which are explicit coercions that prevent some possible behaviours of services and, in doing so, they make services compatible with different usage scenarios. We show that filters can be seen as proofs of a sound and complete subcontracting deduction system which simultaneously refines and extends Hennessy's classical axiomatisation of the must testing preorder. The relation is decidable and the decision algorithm is obtained via a cut-elimination process that proves the coherence of subcontracting as a logical system.</p> <p>Despite the richness of the technical development, the resulting approach is based on simple ideas and basic intuitions. Remarkably, its application is mostly independent of the language used to program the services or the clients. We also outline the possible practical impact of such a work and the perspectives of future research it opens.</p&gt

Isomorphisms of types in the presence of higher-order references (extended version)

We investigate the problem of type isomorphisms in the presence of higher-order references. We first introduce a finitary programming language with sum types and higher-order references, for which we build a fully abstract games model following the work of Abramsky, Honda and McCusker. Solving an open problem by Laurent, we show that two finitely branching arenas are isomorphic if and only if they are geometrically the same, up to renaming of moves (Laurent's forest isomorphism). We deduce from this an equational theory characterizing isomorphisms of types in our language. We show however that Laurent's conjecture does not hold on infinitely branching arenas, yielding new non-trivial type isomorphisms in a variant of our language with natural numbers

Retrieving function components from a reuse library.

Increasing software development productivity is not enough to close the gap between the software demands in industry and software that can be provided in practice. Software reuse is claimed to be the only realistic approach to solve this problem [17]. As the reusable components are growing, we are faced the challenge of modulating, structuring and storing these components into reuse library so as to achieve faster and effective retrieval for reuse. In this thesis we investigate an approach of structuring a function library and an efficient type-based retrieval method based on this structured library. In searching for functions, the trivial difference of the argument order of a function is disregarded. The library structuring is based on component grouping and component linking based on reusability relations among components. A prototype system WISER was also developed as a tool for achieving exact matched retrieval as well as relaxed matched retrieval. WISER also allows users to browse the structured library as an aid in finding potentially reusable components. Paper copy at Leddy Library: Theses & Major Papers - Basement, West Bldg. / Call Number: Thesis1998 .A55. Source: Masters Abstracts International, Volume: 39-02, page: 0524. Adviser: Young G. Park. Thesis (M.Sc.)--University of Windsor (Canada), 1998

Dynamic Order-Sorted Term-Rewriting Systems

This thesis considers the problems of order-sorted equational logic and its operational interpretation, order-sorted term rewriting

Deduction-Based Software Component Retrieval

Deduction-based software component retrieval is a software reuse technique that uses formal specifications as component descriptors and as search keys; matching components are identified using an automated theorem prover. This dissertation contains a detailed theoretical investigation of the concept as well as the first substantial experimental evaluation of its technical feasibility.Deduktionsbasiertes Kompenentenretrieval ist eine Softwarereusetechnik, in der formale Spezifikationen zur Beschreibung von Komponenten sowie als Anfragen verwendet werden; passende Komponenten werden mit Hilfe eines automatischen Theorembeweisers ermittelt. Diese Arbeit enthält eine detaillierte theoretische Untersuchung dieses Konzeptes und die erste ausführliche experimentelle Evaluierung seiner technischen Realisierbarkeit