. This paper surveys the work of many researchers on rewriting logic since it was first introduced in 1990. The main emphasis is on the use of rewriting logic as a semantic framework for concurrency. The goal in this regard is to express as faithfully as possible a very wide range of concurrency models, each on its own terms, avoiding any encodings or translations. Bringing very different models under a common semantic framework makes easier to understand what different models have in common and how they differ, to find deep connections between them, and to reason across their different formalisms. It becomes also much easier to achieve in a rigorous way the integration and interoperation of different models and languages whose combination offers attractive advantages. The logic and model theory of rewriting logic are also summarized, a number of current research directions are surveyed, and some concluding remarks about future directions are made. Table of Contents 1 In...

Abstract. Many organizations nowadays face the problem of accessing existing data sources by means of flexible mechanisms that are both powerful and efficient. Ontologies are widely considered as a suitable formal tool for sophisticated data access. The ontology expresses the domain of interest of the information system at a high level of abstraction, and the relationship between data at the sources and instances of concepts and roles in the ontology is expressed by means of mappings. In this paper we present a solution to the problem of designing effective systems for ontology-based data access. Our solution is based on three main ingredients. First, we present a new ontology language, based on Description Logics, that is particularly suited to reason with large amounts of instances. The second ingredient is a novel mapping language that is able to deal with the so-called impedance mismatch problem, i.e., the problem arising from the difference between the basic elements managed by the sources, namely data, and the elements managed by the ontology, namely objects. The third ingredient is the query answering method, that combines reasoning at the level of the ontology with specific mechanisms for both taking into account the mappings and efficiently accessing the data at the sources.

In this paper, we argue that object-oriented models must be able to represent three kinds of taxonomic structures: static classes, dynamic classes, and role classes, that behave differently with respect to object migration. If CAR is a static subclass of V EHICLE, then a vehicle that is not a car can never migrate to the CAR subclass. On the other hand, if EMP loyee is a dynamic subclass of PERSON object class, then a PERSON that is not an employee may migrate to EMP . In both cases, an instance of the subclass is identical to an instance of the superclass. By contrast, if EMP is modeled as a role class of PERSON , then every employee differs from every person, but a PERSON instance can acquire one or more EMP instances as roles. The distinctions between the three kinds of classes are orthogonal, so that we can have, for example, dynamic subclasses of object or role classes, or role classes of dynamic or static classes. The paper is divided into two parts. In the first, infor...

In this paper, we argue that object-oriented models must be able to represent three kinds of taxonomic structures: static subclasses, dynamic subclasses and role classes. If CAR is a static subclass of V EHICLE, then a vehicle that is not a car can never migrate to the CAR subclass. If EMP loyee is a dynamic subclass of PERSON , then a PERSON that is not an employee may migrate to EMP . In both cases, an instance of the subclass is identical to an instance of the superclass. Finally, if EMP is modeled as a role class of PERSON every employee differs from every person, but a PERSON instance can acquire one or more EMP instances as roles. We outline an approach to formalizing these taxonomic structures in order-sorted dynamic logic with equality. Keywords: Theoretical foundations, formal methods, OO analysis and design February 2, 1994 Contents 1 Introduction 1 2 Methodological aspects of role-playing and class migration 1 2.1 Object classification and identification : : : : : : : : :...

. According to rumors, the early hybrids of object-oriented and deductive languages were mutants that escaped from secret Government AI labs. Whether this is true or not, the fact is that by mid-80's, database and logic programming communities began to take notice. The temptation was hard to resist: the object-oriented paradigm provides a better way of manipulating structured objects, while logic and deduction offer the power and flexibility of ad hoc querying and reasoning. Thus, hybrid languages have the potential for becoming an ideal turf for cultivating the next generation of information systems. The approaches to integration of the two paradigms range from logicbased languages with unified declarative semantics, to message-passing prologs, to Prolog/C++ cocktails. In the past eight years, my colleagues and I have been developing a unified object-based logic intended to capture most of the essentials of the object-oriented paradigm. The overall plot here is that once the fundament...

Rewriting logic is proposed as a logic of concurrent action and change that solves the frame problem and that subsumes and unifies a number of previous logics of change, including linear logic and Horn logic with equality. Rewriting logic can represent action and change with great flexibility and generality; this flexibility is illustrated by many examples, including examples that show how concurrent object-oriented systems are naturally represented. In addition, rewriting logic has a simple formalism, with only a few rules of deduction; it supports user-definable logical connectives, which can be chosen to fit the problem at hand; it is intrinsically concurrent; and it is realizable in a wide spectrum logical language (Maude and its MaudeLog extension) supporting executable specification and programming. Contents 1 Introduction 2 1.1 What the frame problem (in our sense) is . . . . . . . . . . . . . . . . . . . . . . . 2 1.2 What the frame problem (in our sense) is not . . . . . . ....

Abstract. Ontologies provide a conceptualization of a domain of interest. Nowadays, they are typically represented in terms of Description Logics (DLs), and are seen as the key technology used to describe the semantics of information at various sites. The idea of using ontologies as a conceptual view over data repositories is becoming more and more popular, but for it to become widespread in standard applications, it is fundamental that the conceptual layer through which the underlying data layer is accessed does not introduce a significant overhead in dealing with the data. Based on these observations, in recent years a family of DLs, called DL-Lite, has been proposed, which is specifically tailored to capture basic ontology and conceptual data modeling languages, while keeping low complexity of reasoning and of answering complex queries, in particular when the complexity is measured w.r.t. the size of the data. In this article, we present a detailed account of the major results that have been achieved for the DL-Lite family. Specifically, we concentrate on DL-LiteA,id, an expressive member of this family, present algorithms for reasoning and query answering over DL-LiteA,id ontologies,

Nested loop execution of object-oriented queries retains the promise of maintaining the full generality of the object paradigm, independent of the specifics of any single object model. Thus, from this starting point we have developed an object-oriented query optimizer and execution engine. The methods, developed to date for only acyclic queries, augment nested loops structures with a simple marking mechanism such that unnecessary loop iterations are not repeated. In the case of acyclic queries, the executions are asymptotically optimal. In contrast to optimal query methods based on semijoin reductions our method involves no preprocessing step and thus avoids the extra I/O associated with semijoins and prevents the formal benefits of semijoin reduction from appearing as a practical improvement. Empirical results comparing our query environment with a commercially available product demonstrate significant performance improvement. 1 Introduction We develop a technique for the optimizatio...

This paper presents an object-oriented database model for broadband telecommunication networks, which can be used both for network management and for network planning purposes. The object-oriented data model has been developed using the parallel object-oriented specification language Maude [8,11], which allows us to define not only structural aspects of the database, but also procedural aspects. Several modeling approaches are compared, emphasizing the definition of the object relationships and some of the procedural aspects of the model. 1 Introduction Maude is a specification language based on rewriting logic [7], which integrates equational and object-oriented programming in a satisfactory way. Its logical basis facilitates a clear definition of the object-oriented semantics and makes it a good choice for the formal specification of object-oriented systems. Rewriting logic was first proposed by Meseguer as a unifying framework for concurrency in 1990 [6]. Since then much work has b...

Extending a strongly typed object-oriented programming language system technology to an object-oriented database technology requires a high-level, object-oriented specification language that would perform the role of a query language in classical database technologies (for example, the relational one). Our goal is to design and implement such a specification language as a semantic extension of an advanced, polymorphic, object-oriented database type system, so that procedural specification of methods will be abandoned whenever possible. A variety of logic paradigms have been explored in the literature as candidates for the formal basis of such a language (O-logic, F-logic, Horn-clause logic with equality and its extensions, the rewriting logic). Our contribution is in demonstrating that an appropriately defined temporal logic tied with an advanced object-oriented type system is better suited than any of the other candidates for expressing complex behavioral properties of objects and state transitions in particular. On the implementation side of the issue, we demonstrate that our specifications are effectively executable. This observation leads to a prototyping tool as a powerful assistant in designing complex objectoriented systems in strongly typed manner, allowing complex design decisions to be tested structurally and behaviorally prior to the major implementation efforts.