Article pp.7-9 du Vol.9 n°4 (2003)

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Editorial

Object-Oriented technology plays an increasingly important part in engineering software systems. Although the basic features of Object-Oriented have been around for a number of decades, until recently they have been restricted to the implementation phases of project development. Within the last few years, the software industry has started to adopt Object-Oriented techniques in earlier stages of development such as specification and design.

All of the benefits of Object-Oriented technology for programming such as re- use, modularity and abstraction are also claimed for earlier stages. There is clear commercial benefit from this approach: system quality is increased by using modular component based techniques; component designs can be reused due to inheritance and polymorphism; system architectures can be designed for reuse; and there is increased scope for developing software product lines whereby many different products can be generated from a core system description by replacing and extending well-defined components.

Object-Oriented modeling, particularly the Unified Modeling Language (UML), has become widespread. UML is used to construct a model of various aspects of a system including its architecture, static structure and behaviour. New initiatives within the Object-Oriented community, such as Agile Modeling, Aspect Oriented Modeling and Model Driven Architecture, aim to increase the amount of modeling that takes place during system development.

Increased interest in meta-modeling has lead to the development of a number of techniques for Domain Specific Modeling Languages whereby modeling languages are developed whose features and properties are specifically oriented towards the application domain. A number of papers in this volume describe research that aims to increase the quality of software system modeling and UML in particular.

Object-Oriented implementation techniques are now sufficiently mature to be adopted by industries such as defence and aviation where safety issues and real-time issues are very important. In order to support these critical features, Object- Oriented methods must be supported by formal techniques that allow developers to reason about the properties of the system. A number of papers in this volume show how Object-Oriented formal techniques can be applied to software development.

As Object-Oriented spreads, there is an increased need for rigorous methods that guide the developer in the use of the supporting technology. The aim of the

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8 RSTI - L’Objet – 9/2003. Rigorous Object-Oriented Methods

ROOM workshop series is to provide a forum where researchers into rigorous object-oriented methods for system development can report and discuss recent results. The series has successfully held four workshops at Imperial College (1997), University of Bradford (1998), University of York (2000) and King’s College London (2001). This volume of the journal L’Objet contains a number of key papers from the workshop held at King’s College in March 2002.

The paper by France, Ghosh and Turk provides an overview of the issues relating to the use of Object-Oriented modeling in Industry. It proposes that there are problems with current modeling methods and notations and proposes a new approach based on designing specific modeling languages and using recurring patterns in systems to address different aspects of a system including such properties as safety and fault-tolerance. The advantage of their approach is that key properties of a system can be addressed individually thereby increasing the scope for quality control.

Commercial interest is growing in the potential of MDA whereby the focus of development effort is moved from the details of delivery platforms to abstract models. Standard transformations are used to produce implementations on many different platform architectures from the same model. There are clear benefits from this approach to Industry: models are easier to develop, maintain and reuse.

However, the technology used to translate from models to implementations is in the early stages of development. The paper by Clark, Evans, Kent, Maskeri, Sammut and Willans makes a contribution in the area by proposing a standard architecture for defining transformations.

Notation used to model the static aspects of systems is very mature in comparison with the notations used to express the dynamic aspects. With respect to the UML notation, there is broad agreement regarding the meaning of class diagrams and there are many tools that translate class diagrams to program skeletons. There is much less agreement on the meaning of dynamic aspects of UML; as a consequence many UML tools provide good support for class diagrams whilst being very weak with respect to notations such as statecharts and collaboration diagrams. The paper by Lano, Clark and Androutsopoulos makes a contribution by proposing a formal model for class diagrams and statecharts and a route to analysis of dynamic properties via a translation to SMV. In addition, the paper by Royer shows how to formally verify dynamic properties of a UML model by translating models, including OCL expressions, into a form suitable for the Larch Theorem Prover.

As modeling is becoming widespread, there is increasing interest in defining bespoke notations for specific application areas. The UML notation provides profiles and stereotypes as mechanisms for tailoring the notation; there are profiles for Ada, real-time systems and telecomms applications. It is usual to define a new notation in terms of a meta-model that specifies the structure and semantics of a new notation. Meta-modeling is an area of study in its own right, for example the UML

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Editorial 9

meta-model is expressed in a notation called MOF that is itself meta-modelled in MOF. Such circularities in language design raises a number of interesting problems that are addressed by the paper by Barr.

As modeling technologies are applied to increasingly large applications it has become apparent that there is a management issue relating to models of entire systems. This has lead to constructing system as a collection of interrelated aspects or views. A system has aspects including its static structure and dynamic behaviour, its quality of service, and its security. Each aspect is expressed using a suitable notation; each notation has its own semantics. The resulting collection of aspect models must be reconciled. The paper by Paige describes how PVS theorem proving technology can be used to test the integrity of multiple aspect models.

Tony Clark, King’s College London

Andy Evans,

Kevin Lano, King’s College London