COOPN/2 : A Specification Language for Distributed Systems Engineering

In this article we present the concurrent object-oriented specification language COOPN/2 which extends the COOPN (Concurrent Object Oriented Petri Nets) formalism, destined to support the development of large heterogenous distributed systems. The development of distributed applications has recently been the subject of intensive research, due to potential benefits that can be expected to offer in increasing reliability and overall performance of computer processing. One way of improving the effectiveness of the distributed system construction is to adopt a rigorous approach for system development, based on structuring principles. The COOPN/2 approach proposes a specification language, based on the object-oriented paradigm, which includes a fine description of true concurrent behaviors. This hybrid approach (model and property-oriented) allows for a description of the concurrent aspects through the use of a high-level Petri nets formalism which includes data structures expressed with the algebraic abstract data types and a synchronization mechanism for building hierarchies of abstraction. This latter notion is the concept which is used in structuring applications. Interesting properties of COOPN, such as the progressive refinement of specifications, allow for the building of systems in an incremental manner.In this article, we introduce COOPN/2 informally, by means of a typical example of distributed systems, the transit node, in order to introduce each useful and innovative mechanism of the language. Then, in the context of distributed software engineering with COOPN/2, we present our current works done in order to provide formal methods for several steps of a life cycle model test, prototyping, analysis,....). Keywords: software engineering, formal specification language, refinement, prototyping, distributed systems, object orientation, concurrency, Petri nets, algebraic specification.

Formal Development of Java Programs

The Java object-oriented programming language has been the subject of an important involvement from programmers and industry. Especially for applications related to the Web. The problem of such rapid penetration of Java programs into commercial product is that software engineers does not have any methodology and have to develop complex parallel applications. In this paper, we present, using a real (http://lglsun.epfl.ch/Team/GDM/DSGamma.html) but simple Web parallel application, a possible formal development methodology based on the stepwise refinement of CO-OPN/2 formal specifications. The application chosen is based on the Gamma paradigm, in which additions are realized across distributed multisets of integers maintained by local Java applets. CO-OPN/2 is an object-oriented specification formalism allowing the formal specification of abstract data types based on algebraic specification and of concurrent objects using a Petri net like approach. An interesting feature of CO-OPN/2 is that it gives a coherent solution for the expression of complex properties combining inheritance, concurrency and synchronizations. The refinement of formal descriptions for building progressively the Java program is presented in several refinement steps. This refinement process focuses on the distribution of data and treatments, and validation and verification are studied through the refinement of system properties.

1997

Stepwise refinement of formal specifications based on logical formulae

One of the steps making it possible to increase the quality and the reliability of the software executing on distributed systems consists of the use of methods of software engineering that are known as formal. The majority of the formal methods currently existing correspond in fact more to formal specifications languages than to methods themselves. This is due to the fact that the two fundamental aspects which are: the logic of use of the language and the coverage of the software life cycle are not, for the majority, defined. The development by stepwise refinement is one of the means making it possible to define these two aspects. This thesis aims to the definition of the concepts of refinement and implementation of model-oriented formal specifications. It brings a methodological base making it possible to use such a specifications language during a development by stepwise refinements and during the implementation stage. This thesis defines, initially, a theoretical framework for the refinement and the implementation of formal specifications. The main idea consists in associating a contract with each specification. A contract explicitly represents the whole of the properties of the specification which it is necessary to preserve at the time of a refinement of this specification. To show that a concrete specification refines some abstract specification, it is then a matter of showing that the contract of the concrete specification is sufficient to ensure the properties corresponding to the contract of the abstract specification. The second part of this thesis consists in applying this theoretical framework in the context of the CO-OPN/2 language. CO-OPN/2 is an object-oriented formal specifications language founded on algebraic specifications and Petri nets. Thus, definitions of the concepts of contracts, refinement and implementation are proposed for this language. The contracts are expressed using the Hennessy-Milner temporal logic (HML). This logic is used in the theory of test provided with language CO-OPN/2. Thus, the verification of the contractual properties, as well as the verification of the stages of refinement are facilitated. Refinement and implementation are controlled semantically by the satisfaction of the contracts; syntactically, a renaming is authorised. We specifically study the implementation using the Java programming language. We show how to specify classes of the Java programming language using language CO-OPN/2, so that the last stage of the process of refinement leads to a specification entirely built using CO-OPN/2 components specifying Java classes. The stage of implementation in the Java language itself is thus facilitated. The third part of this thesis shows how it is possible to practically verify that a CO-OPN/2 specification satisfies its own contract, that a stage of refinement is correctly carried out, and finally that the stage of implementation is correctly performed. These verifications are carried out using the theory of the test provided with language CO-OPN/2. Finally, the last part of this thesis illustrates the cogency of this approach by applying it to a complete and detailed case study. A distributed Java application is developped according to the method introduced for the CO-OPN/2 language. Refinement is guided mainly by the satisfaction of functional requirements and by constraints of design integrating the concept of client/server architecture. Lastly, the stages chosen in the refinement process of this development make it possible to study aspects specific to distributed applications, and to propose generic schemas for the design of such applications.

EPFL1999

Stepwise Refinement of Formal Specifications Based on Logical Formulae: from COOPN/2 Specifications to Java Programs

1999

Stepwise Refinement of Formal Specifications Based on Logical Formulae: from COOPN/2 Specifications to Java Programs

1999

Stepwise refinement of formal specifications based on logical formulae

EPFL1999