Grit Denker

Logics for specifying concurrent information systems

This chapter concentrates on a challenging problem of information system specification and design, namely how to cope on a high level of abstraction with concurrent behaviour and communication as implied by distribution. Since distributed information systems are reactive and open systems maintaining data bases and applications, it is crucial to develop high-level specification techniques that can cope with data and programs as well as with concurrent workflow and communication issues. Techniques from conceptual modeling, abstract data types, concurrent processes and communication protocols are relevant and have to be combined. In the approach presented here, temporal logic is used for specifying sequential object behaviour, and communication facilities are added for specifying interaction between concurrent objects. We study two distributed temporal logics dealing with communication in two different ways. D0 adds basic statements that can only express synchronous “calling” of predicates, while D1 adds much richer facilities for making local statements about other objects in their respective local logics. D0 is more operational and can be animated or implemented more easily, while D1 is intuitively more appealing and convenient for modeling and specification. We demonstrate by example how D1 can be effectively reduced to D0 in a sound and complete way.

Information systems modelling with TROLL formal methods at work

Abstract 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.

Constructing Systems as Object Communities

We give a survey of concepts for system specification and design based on the viewpoint that a system is a community of objects. Objects are self-contained units of structure and behavior capable of operating independently and cooperating concurrently. Our approach integrates concepts from semantic data modeling and concurrent processes, adopting structuring principles partly developed in the framework of object-orientation and partly in that of abstract data types. A theory of object specification based on temporal logic is briefly outlined.

Integrating the ER Approach in an OO Environment

We translate Entity-Relationship (ER) schemas into the object-oriented specification language TROLL light. This language describes the Universe of Discourse (UoD) as a system of concurrently existing and interacting objects, i.e., an object community. Thereby two essential aspects, structure and behavior, are integrated in one formalism. By doing the translation from ER to TROLL light we preserve the visual advantages of the former and receive a formalism through the latter which can be mapped to an adequate object-oriented database system. Proceeding this way we hope our proposal for transforming ER schemas into TROLL light specifications provides a valuable link between structural and dynamic modeling.

Towards Reliable Information Systems: The KorSo Approach

Within the compound project KorSo our team is concerned with the research on techniques and methods for the development of reliable information systems on the basis of formal specifications. Our work focuses on the specification language TROLL light which allows to describe the part of the world which is to be modeled as a community of concurrently existing and communicating objects by determining their structure as well as their behavior. Moreover we develop and implement a computer aided specification environment for TROLL light which permits a prototyping animation as well as the proof of properties of specifications.

Developing an Information System Using TROLL: An Application Field Study

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 effects in the future.

A Linear Temporal Logic Approach to Objects with Transactions

Our concern is the high level specification of reactive software systems such as information systems. We adopt an object oriented, temporal logic based approach to specification. The notion of transaction incorporates various application domains, for instance transactions as abstractions from processes as known from refinement theory, transactions as abstractions from business processes as known in business process modelling or database transactions. In this paper we investigate object specifications with transactions. We illustrate the use of transactions by examples given in an object oriented style and introduce a linear temporal logic with transactions (Tosl) which serves as denotional model for such object specifications with transactions. We explain how Tosl is semantically defined in terms of life cycles and illustrate by example the translation of object specifications to Tosl. Using Tosl for system specification results in sets of formulae which are independent from the level of granularity.

TROLL light - The Language and its Development Environment

In our sub-project we are concerned with techniques for the development of reliable information systems on the basis of their formal specification. Our work focuses on the specification language TROLL light which allows to describe the part of the world to be modeled as a community of concurrently existing and communicating objects. Our specification language comes along with an integrated, open development environment. The task of this environment is to give support for the creation of correct information systems. Two important ingredients of the environment to be described here in more detail are the animator and the proof support system.

Object-Oriented Design of Information Systems: Theoretical Foundations

Information systems are reactive systems with a database. For their specification and design, concepts from conceptual data modeling and concurrent processes are relevant. In this paper, we outline a unifying theory borrowing ideas from these approaches and from abstract data type theory. Our approach utilizes a variant of temporal logic. It has been used to give a formal semantics for TROLL, the object-oriented information systems specification language developed at TU Braunschweig.

Translating TROLL light Concepts to Maude

The specification language TROLL light is designed for the conceptual modeling of information systems. Maude is a logic programming language, which unifies the two paradigms of functional and concurrent object-oriented programming. Because of the very similar features offered by both languages, we present a translation from TROLL light concepts into the Maude language in order to compare the languages. Apart from presenting the translation, the languages are briefly described and illustrated by examples.