Behavioural theories are a generalization of first-order theories where the equality predicate symbol is interpreted by a behavioural equality of objects (and not by their identity). In this paper we first consider arbitrary behavioural equalities determined by some (partial) congruence relation and we show how to reduce the behavioural theory of any class of algebras to (a subset of) the standard theory of some corresponding class of algebras. This reduction is the basis of a method for proving behavioural theorems whenever an axiomatization of the behavioural equality is provided. Then we focus on the important special case of (partial) observational equalities where two elements are observationally equal if they cannot be distinguished by observable computations over some set of input values. We provide general conditions under which an obvious infinite axiomatization of the observational equality can be replaced by a finitary one and we provide methodological guidelines for finding such...

“In software engineering people often believe a state is a node in a graph and don’t even care about what a state means in reality.” David Parnas, 1998 This note clarifies the concept of syntax and semantics and their relationships. Today, a lot of confusion arises from the fact that the word “semantics ” is used in different meanings. We discuss a general approach at defining semantics that is feasible for both textual and diagrammatic notations and discuss this approach using an example formalization. The formalization of hierarchical Mealy automata and their semantics definition using input/output behaviors allows us to define a specification, as well as an implementation semantics. Finally, a classification of different approaches that fit in this framework is given. This classification may also serve as guideline when defining a semantics for a new language. 1

The World-Wide Web is changing the nature of software development to a distributive plug & play process. This requires a new way of managing software by so-called intelligent software brokers. The aim of the European IBROW3 project is to develop an intelligent brokering service that enables third party knowledge-component reuse through the World-Wide Web. Suppliers provide libraries of knowledge components adhering to some standard, and customers can consult these libraries -- through intelligent brokers -- to configure a knowledge system suited to their needs by selection and adaptation. IBROW3 integrates research on heterogeneous databases, interoperability and web technology with knowledge-system technology and ontologies. The aim is to develop a broker that can handle web requests for classes of knowledge system (e.g. diagnostic systems) by accessing libraries of reusable problem-solving methods on the Web, and selecting, adapting and configuring these methods in accor...

algorithms for copies convergence

This article presents a new formal approach to testing. In the field of dynamic testing, as soon as a program fails for a test set, it is flagged incorrect. The remaining question is: how far can a successful program be considered as correct? We give a definition of program correctness with respect to a specification which is adequate to dynamic testing. Similarly to the field of abstract implementation, the idea is that in order to declare a program as correct, it suffices that its behavior fulfills the specification requirements. An intermediate semantic level between the program and the specification, called the oracle framework, is introduced in order to interpret observable results obtained from dynamic experiments on the program. This allows to give algebraic semantics (i.e. a set of models) to the program, compatible with the program behavior. Program correctness is then defined by some adequacy criterion between the specification semantics and the program semantics. We point ou...

A model theory for proving correctness of abstract data types is developed within the framework of the behavior-realization adjunction. To allow for incomplete specifications, proof-of-correctness ...

. Currently much effort is being spent on providing objectoriented databases with ad hoc query facilities. In this paper we present a SQL-like query calculus whose major contribution lies in its inherent orthogonality and rigorous mathematical foundation. The calculus is essentially a calculus of complex values but it is defined independently of any concrete database model. The calculus can be used to formulate queries in value-based and object-based data models. Moreover it provides a general facility for the manipulation of complex values. 1 Introduction Object-oriented database systems (OODB) are usually embedded in a programming language environment providing full computational power. Consequently, designers of OODB at first did not feel the need to integrate ad hoc query facilities into their systems. However, it has been recognized that some associative retrieval is of importance even for OODB [8, 12, 13]. A well-tried ad hoc query language is SQL. SQL came up with relational da...

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During the last years, a number of formal specification languages for knowledge-based systems has been developed. Characteristic for knowledge-based systems are a complex knowledge base and an inference engine which uses this knowledge to solve a given problem. Specification languages for knowledge-based systems have to cover both aspects. They have to provide means to specify a complex and large amount of knowledge and they have to provide means to specify the dynamic reasoning behaviour of a knowledge-based system. This paper focuses on the second aspect. For this purpose, we survey existing approaches for specifying dynamic behaviour in related areas of research. In fact, we have taken approaches for the specification of information systems (Language for Conceptual Modelling and TROLL), approaches for the specification of database updates and logic programming (Transaction Logic and Dynamic Database Logic), and the generic specification framework of Abstract State Machines. Keywords...

this paper, we will describe the main techniques for the semantic definition of some of the most used structuring and modular constructs. Our main aim will be to study the generic, "institutionindependent ", version of each construct. However, in order to provide intuition, in most cases, we will first study these constructions in connection to equational logic.