The very success and breadth of reflective techniques underscores the need for a general theory of reflection. At present what we have is a wide-ranging variety of reflective systems, each explained in its own idiosyncratic terms. Metalogical foundations can allow us to capture the essential aspects of reflective systems in a formalismindependent way. This paper proposes metalogical axioms for reflective logics and declarative languages based on the theory of general logics [34]. In this way, several strands of work in reflection, including functional, equational, Horn logic, and rewriting logic reflective languages, as well as a variety of reflective theorem proving systems are placed within a common theoretical framework. General axioms for computational strategies, and for the internalization of those strategies in a reflective logic are also given. 1 Introduction Reflection is a fundamental idea. In logic it has been vigorously pursued by many researchers since the fundamental wor...

It is well known that interpolation properties of logics underlying specification formalisms play an important role in the study of structured specifications, they have also many other useful logical consequences. In this paper, we solve the interpolation problem for Grothendieck institutions which have recently emerged as an important mathematical structure underlying heterogenous multi-logic specification. Our main result can be used in the applications in several different ways. It can be used to establish interpolation properties for multi-logic Grothendieck institutions, but also to lift interpolation properties from unsorted logics to their many sorted variants. The importance of the latter resides in the fact that, unlike other structural properties of logics, many sorted interpolation is a non-trivial generalisation of unsorted interpolation. The concepts, results, and the applications discussed in this paper are illustrated with several examples from conventional logic and algebraic specification theory.

The Semantic Web should enable greater access not only to content but also to services on the Web. Users and software agents should be able to discover, invoke, compose, and monitor Web resources o ering particular services and having particular properties. As part of the DARPA Agent Markup Language program, we have begun to develop an ontology of services, called DAML-S, that will make these functionalities possible. In this white paper we describe the overall structure of the ontology, the service pro le for advertising services, and the process model for the detailed description of the operation of services.

In this article we present a functional specification language based on inclusions between set expressions. Instead of computing with data individuals we deal with their classification into sets. The specification of functions and relations by means of inclusions can be considered as a generalization of the conventional algebraic specification by means of equations. The main aim of this generalization is to facilitate the incremental refinement of specifications. Furthermore, inclusional specifications admit a natural visual syntax which can also be used to visualize the reasoning process. We show that reasoning with inclusions is well captured by bi-rewriting, a rewriting technique introduced by Levy and Agust'i [15]. However, there are still key problems to be solved in order to have executable inclusional specifications, necessary for rapid prototyping purposes. The article mainly points to the potentialities and difficulties of specifying with inclusions.

The background for this paper is twofold: Oneisthedefinition of a caching protocol for shared memory parallel computers called SCI, andthe other is the usage of rewritingtechniques in program verification. The paper concentrates on a linked list system, which is a central aspect of thecaching protocol. Wefirstdescribe an informal proof of this system, includingarather large invariant. Thereafter weshowhowthe list system andtheinvariant can both be described in the formalism of rewriting logic, andweusethis to carry through a significant part of theverification mechanically,usingtheOBJ3interpreter.

Abstract. Modern software systems are increasingly being developed for deployment on a range of architectures. For this purpose, it is interesting to capture aspects of low-level deployment concerns in high-level modeling languages. In this paper, an executable object-oriented modeling language is extended with resource-restricted deployment components. To analyze model behavior a formal methodology is proposed to assess resource consumption, which balances the scalability of the method and the reliability of the obtained results. The approach applies to a general notion of resource, including traditional cost measures (e.g., time, memory) as well as concurrency-related measures (e.g., requests to a server, spawned tasks). The main idea of our approach is to combine reliable (but expensive) worst-case cost analysis of statically predictable parts of the model with fast (but inherently incomplete) simulations of the concurrent aspects in order to avoid the state-space explosion. The approach is illustrated by the analysis of memory consumption. 1

Abstract. This paper shows a rigorous approach based on algebraic speci cations and rewriting logic which makes up for the lack of current transformation languages and o ers a balanced rigour-versus-intuition framework for model transformation, focusing on the MDA-QVT standards. To illustrate this approach, an example and some formal applications of these speci cations are sketched. 1

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