Mediator modules provide intermediary services in information systems, linking data resources and application programs. Programs that led to the concept of mediation were either constructed to support specific applications, or extended services from databases. Mediators are being built now by careful domain knowledge acquisition and hand crafting the required code. In this paper we present the conceptual underpinning for automating the mediation process. Our goal is not fully automatic code generation, since programming knowledge is necessary to provide the added value that offsets the costs of having the extra architectural layer due to formal mediation. The concept is based on the extraction of a hierarchical domain model out of the general network representing the available resources. Associated with the method are domain ontologies. Ontologies list the terms used by the models, and document their relationships. These terms provide the semantic foundation needed to perform the match...

This paper addresses the problem of how to construct refinements of specifications formally and incrementally. The key idea is to use a taxonomy of abstract design concepts, each represented by a design theory. An abstract design concept is applied by constructing a specification morphism from its design theory to a requirement specification. Procedures for propagating constraints, computing colimits, and constructing specification morphisms provide computational support for this approach. Although we conjecture that classification generally applies to the incremental application of knowledge represented in a taxonomy of design theories, this paper mainly focuses on algorithm design theories and presents several examples of design by classification.

Ontology concerns itself with the representation of the objects in the universe and the web of their various connections. The traditional task of ontologists has been to extract from this tangle a single ordered structure, in the form of a tree or lattice. This structure consists of the terms that represent the objects, and the relationships that represent connections between objects. Recent work in ontology goes so far as to consider several distinct, superimposed structures, which each represent a classification of the universe according to a particular criterion. Our purpose is to defer the task of globally classifying terms and relationships. Instead, we focus on composing them for use as we need them. We define contexts to be our unit of encapsulation for ontologies, and use a rule-based algebra to compose novel ontological structures within them. We separate context from concept, the unit of ontological abstraction. Also, we distinguish composition from subsumption, or containment, the relationships that commonly provide structure to ontologies. Adding a formal notation of encapsulation and composition to ontologies leads to more dynamic and maintainable structures, and, we believe, greater computational efficiency for knowledge bases.

Eliciting the requirements for a proposed system typically involves different stakeholders with different expertise, responsibilities, and perspectives. Viewpoints-based approaches have been proposed as a way to manage incomplete and inconsistent models gathered from multiple sources. In this paper, we propose a category-theoretic framework for the analysis of fuzzy viewpoints. Informally, a fuzzy viewpoint is a graph in which the elements of a lattice are used to specify the amount of knowledge available about the details of nodes and edges. By defining an appropriate notion of morphism between fuzzy viewpoints, we construct categories of fuzzy viewpoints and prove that these categories are (finitely) cocomplete. We then show how colimits can be employed to merge the viewpoints and detect the inconsistencies that arise independent of any particular choice of viewpoint semantics. We illustrate an application of the framework through a case-study showing how fuzzy viewpoints can serve as a requirements elicitation tool in reactive systems. 1

This article presents a theory of classes and inheritance built on top of constructive type theory. Classes are defined using dependent and very dependent function types that are found in the Nuprl constructive type theory. Inheritance is defined in terms of a general subtyping relation over the underlying types. Among the basic types is the intersection type which plays a critical role in the applications because it provides a method of composing program components. The class theory is applied to defining algebraic structures such as monoids, groups, rings, etc. and relating them. It is also used to define communications protocols as infinite state automata. The article illustrates the role of these formal automata in defining the services of a distributed group communications system. In both applications the inheritance mechanisms allow reuse of proofs and the statement of general properties of system composition. 1

this paper functional languages are proposed as such a methodology using an extension of the concept of skeletons --- higher-order functions coupled with parallel implementation templates. An essential part of the proposed methodology is the use of data distribution algebras

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This paper describes a method for applying formal specifications to automate a system design process based on reusable components and architectures. The focus is on identification and retrieval of components pertinent to a problem, and selection and application of architectures available for adapting these components. Component retrieval is facilitated by a heuristic based on specification semantics for approximating specification matches that indicate component reusability. To support adaptation, a formal model of architectures is developed that uses algebraic theories to specify relationships between the system and component specifications. Adaptation is performed by placing or replacing components within an architecture theory. Keywords Software reuse, specification-based retrieval, software architecture formalisms. INTRODUCTION As software systems are becoming larger and more complex, the demand for high levels of reliability and productivity is also increasing. New techniques ...

Formal methods are usually conceived as a way to obtain veri ably correct software, so many researchers have focused on applications requiring error-free code, such as safety-critical subsystems. There may be other paths to the ultimate success of formal methods. We argue that mechanized synthesis tools can have an impact in the production of high-performance algorithms. This thesis is supported by our work on the synthesis of transportation scheduling algorithms. 1

The connection between some modularity properties and interpolation is revisited and restated in a general "logicindependent " framework. The presence of uniform interpolants is shown to assist in certain proof obligations, which suffice to establish the composition of refinements. The absence of the desirable interpolation properties from many logics that have been used in refinement, motivates a thorough investigation of methods to expand a specification formalism orthogonally, so that the critical uniform interpolants become available. A potential breakthrough is outlined in this paper. 1. A refinement paradigm Let us consider program development by means of stepwise refinements. One postulates some abstract data typelike specification 1 (ADT), suitable for the problem at hand, which has to be implemented on the available system. The end product consists of (the text of) an abstract program manipulating the postulated ADT, together with a suite of (texts of) modules implementin...