The envisaged notion of object is presented as corresponding to the basic, universal building block of (information) systems. A simple mathematical model for fully concurrent objects (actors) is adopted that extends a suitable model for sequential processes. An object is defined as a process possibly endowed with initiative and tracedependent attributes. Transactional requirements are analysed within this framework as liveness requirements. Object aggregation is explained using the general notion of object morphism. The basic inheritance, overriding and reification mechanisms are also presented, as well as a suitable notion of object-type. The computational model is shown through examples to provide a sound basis for (information) systems design, including abstract conceptual modeling and layered implementation of both passive (record-like) and active (procedure-like) objects. The model establishes a suitable semantic domain for the envisaged broad spectrum specification/design languag...

The purpose of a logical framework such as LF is to provide a language for defining logical systems suitable for use in a logic-independent proof development environment. All inferential activity in an object logic (in particular, proof search) is to be conducted in the logical framework via the representation of that logic in the framework. An important tool for controlling search in an object logic, the need for which is motivated by the difficulty of reasoning about large and complex systems, is the use of structured theory presentations. In this paper a rudimentary language of structured theory presentations is presented, and the use of this structure in proof search for an arbitrary object logic is explored. The behaviour of structured theory presentations under representation in a logical framework is studied, focusing on the problem of "lifting" presentations from the object logic to the metalogic of the framework. The topic of imposing structure on logic presentations...

. Combined logics have recently deserved much attention. In this paper we develop a detailed study of a form of combination that generalises the temporalisation construction proposed in [9]. It consists of replacing an atomic part (formal parameter) of one (parameterised) logic by another (actual parameter) logic. We provide a categorial characterisation of parameterisation and illustrate it with an example. Under reasonable assumptions, we show that the result logic is a conservative extension of both the parameterised and parameter logics and also that soundness, completeness and decidability are transferred. 1 Introduction We need to work with evermore complex systems. The challenge is to identify abstractions that may lead to a modular and integrated management of this complexity. One such approach is the combination of logics. In practice, it is geared by the need for integrating heterogeneous platforms and tools. Theoretically, the study of logics for combined structures has bee...

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.

In this paper we continue previous work from Sannella, Sokolowski and Tarlecki on parameterization in specification languages. Within the loose approach, we define specification and model level semantics for two kinds of parameterizations (parameterized specifications and specifications of parameterized data types) and describe, in a compositional manner, parameter passing at the two levels. Moreover, the specification and the model level semantics of parameter passing are shown to be compatible. We also show that the results obtained do not only apply to the loose approach but can also be directly applicable to the initial framework, and in general to any other kind of monomorphic framework (i.e. a framework where all specifications are monomorphic). In particular, the results obtained generalize and extend previous results for the initial approach. Finally, for obtaining all our results, new categorical constructions of multiple pushouts, amalgamations and extensions, gen...

Reification is a popular technique to reduce complexity of the software design process. This technique has to be re-investigated for the comprehensive objectoriented approach. Object-oriented specifications comprise structure and behavior of systems. Due to this sophisticated idea two kinds of reification appear: data reification and action reification. In this paper we present an approach to incorporate action reification in object-oriented specification. A logic is defined which serves as a domain to translate specifications. Moreover, we define a language for reification and formalize it with the logic. Interpretation structures of this logic are labelled event structures which are introduced briefly and satisfaction of formulas is defined. With an example we explain our ideas of correct reification and establish a reification condition. Finally, we show how data reification is uniformly included in our approach.

One of the crucial operations on the path from specification to implementation is the modification of data structures. In this paper we demonstrate how this task can be accomplished constructively and, in particular, how it can be done within the Korso methodology. 1 Introduction One of the central activities in the course of the development of a software system is the realization of "abstract" data structures by "more concrete" ones. Originally, this task was only considered in the specific case, where an abstractly specified data type was "implemented" in terms of a concrete data type of a given programming language. But it soon became clear that the same principle also applied in situations where the "concrete" type was actually only specified algebraically. Thus, implementation became a step-by-step process, leading through several stages of algebraic specifications -- which were, however, more and more concrete -- until one eventually arrived at the level of a given programming ...

One of the crucial operations on the path from specification to implementation is the modification of data structures. In this paper we demonstrate how this task can be accomplished constructively and, in particular, how it can be done within the Korso methodology. 1 Introduction One of the central activities in the course of the development of a software system is the realization of "abstract" data structures by "more concrete" ones. Originally, this task was only considered in the specific case, where an abstractly specified data type was "implemented" in terms of a concrete data type of a given programming language. But it soon became clear that the same principle also applies in situations where the "concrete" type was actually only specified algebraically. Thus, implementation became a step-by-step process, leading through several stages of algebraic specifications -- which were, however, more and more concrete -- until one eventually arrived at the level of a given programming ...

Data Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 4.5.4 Special Approaches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 4.6 Semantics of Programming Languages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52 4.6.1 Semantics of Ada . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52 4.6.2 Action Semantics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52 4.7 Specification Languages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53 4.7.1 Early Algebraic Specification Languages . . . . . . . . . . . . . . . . . . . . . . . . 53 4.7.2 Recent Algebraic Specification Languages . . . . . . . . . . . . . . . . . . . . . . . 55 4.7.3 The Common Framework Initiative. . . . . . . . . . . . . . . . . . . . . . . . . . . 56 5 Methodology 57 5.1 Development Phases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57 5.1.1 Applica...

. One of the crucial operations on the path from specification to implementation is the modification of data structures. In this paper we demonstrate how this task can be accomplished constructively. 1 Introduction One of the central activities in the course of the development of a software system is the realization of "abstract" data structures by "more concrete" ones. Originally, this task was only considered in the specific case, where an abstractly specified data type was "implemented" in terms of a concrete data type of a given programming language. But it soon became clear that the same principle also applies in situations where the "concrete" type was actually only specified algebraically. Thus, implementation became a step-by-step process, leading through several stages of algebraic specifications -- which were, however, more and more concrete -- until one eventually arrived at the level of a given programming language. The concept of "implementing" one algebraic specifica...