Abstract not found

Introduction From an object-oriented point of view, software systems are considered to be dynamic collections of autonomous objects that interact with each other. Autonomy means that each object encapsulates all features needed to act as an independent computing agent: individual attributes (data), methods (operations) , behavior (process), and communication facilities. And each object has a unique identity that is immutable throughout lifetime. Coincidentally, objectorientation comes with an elaborate system of classes and types, facilitating structuring and reuse of software. The object approach is widely accepted in software technology, and there are object-oriented programming languages, database systems, and software development methods. The basic idea is not new, because essential features were already present in the programming language Simula [DMN67]. Wider acceptance came with Smalltalk [KG76, GR83]. While the object approach is success

. In this paper, we present two logics that allow for specifying distributed information systems, emphasizing communication among sites. The low-level logic D 0 offers features that are easy to implement but awkward to use for specification, while the high-level logic D 1 offers convenient specification features that are not easy to implement. We show that D 1 specifications may be automatically translated to D 0 in a sound and complete way. In order to prove soundness and completeness, we define our translation as a simple map of institutions. Our result may be useful for making implementation platforms like Corba easier accessible by providing high-level planning and specification methods for communication. 1 Introduction Two logics are presented that allow for specifying distributed information systems, emphasizing communication among sites. The low-level logic D 0 offers features that are easy to implement but awkward to use for specification, while the high-level logic D 1 offers...

Information systems are open, reactive, and often distributed systems that maintain persistent data. The Troll and omTroll languages aim at specifying information systems on a high level of abstraction, supported by tools integrated in the Tbench. The development is rooted in abstract data types, conceptual modeling, behavior modeling, specification of reactive systems, and concurrency theory.

We present fundamentals of an approach to object-oriented specification of distributed information systems. We do not assume global time for concurrent object systems. For specifying those systems we propose Dtl, a distributed temporal logic. The main contribution is that Dtl is capable of specifying complex constraints about the behavior of distributed systems and communication between concurrent objects. For instance, we distinguish different kinds of synchronous communication such as immediate calling vs. deferred calling. The ideas are illustrated by examples given in Troll, a formal object-oriented specification language. We introduce notations for formally specifying object-based distributed systems. Finally, we briefly explain how Dtl is semantically explained in terms of a true concurrent model, i.e., labelled event structures, and which concepts for in-the-large specification are covered by our approach. Keywords Object orientation, specification language, distributed system...

The formal step by step development of implementations from specifications is necessary to allow the incremental description of large software systems and hence split the software development process in manageable portions. Due to the complex notion of objects as units of structure and behavior, the refinement process has to be reconsidered in the object-oriented framework. Apart from refining structure the behavioral part gives rise to refine actions by transactions. Referring to information systems as application domain, concurrency control aspects come into play because of shared resources. We present an approach to incorporate transactions into object-oriented specification and illustrate the main problems of synchronizing them on commonly used resources.

In this paper we present a national project located in the area of computer aided testing and certifying (CATC) of physical devices. The objective of this project is to develop an information system that supports the various activities of different user groups in a German federal institute of weights and measures. We decided to use formal methods right from the beginning of the project. Our approach is based on the formal object oriented specification language Troll. Starting point of the development is an abstract model of the organization which will serve later on as a formal basis for implementation. We present parts of this specification and its relations with the underlying formal semantics. The experiences we made so far are rather positive and we expect further positive effects in the future. Copyright c fl1997 Elsevier Science Ltd Key words: Object Oriented Specification, Case Study, Information System, Information Modelling, Requirements Engineering, Formal Method 1...

The aim of our work is the modelling and design of information systems in the object-oriented setting. An object-oriented specification covers structural as well as behavioural aspects of the system.

From an arbitrary temporal logic institution we show how to set up the corresponding institution of objects. The main properties of the resulting institution are studied and used in establishing a categorial, denotational semantics of several basic constructs of object specification, namely aggregation (parallel composition), interconnection, abstraction (interfacing) and monotonic specialization. A duality is established between the category of theories and the category of objects, as a corollary of the Galois correspondence between these concrete categories. The special case of linear temporal logic is analysed in detail in order to show that categorial products do reflect interleaving and reducts may lead to internal nondeterminism. Key words: object-orientation, system specification, temporal logic, institution, denotational semantics, duality. 1 Introduction The advantages of object-orientation in software engineering in general and system specification in particular...

The general aim of our work is the specification of distributed information systems, that means reactive systems consisting of one or more databases and application programs. In this context the formal object oriented specification language Troll was developed and is now going to be extended by module concepts. In this paper we give a short introduction in Troll and a survey over related work done not only in the object oriented setting but also in the fields of specification languages in general, theory of abstract data types and parameterized programming. When presenting our own module concepts we explicitly distinguish between providing the possibility to structure a large system on one hand and supporting the reuse of (parts of) specifications on the other hand.