The model-driven development of systems involves multiple models, metamodels and transformations, and relationships between them. A bidirectional transformation (bx) is usually defined as a means of maintaining consistency between “two (or more)” models. This includes cases where one model may be generated from one or more others, as well as more complex (“symmetric”) cases where models record partially overlapping information. In recent years, binary bx, those relating two models, have been extensively studied. Multiary bx, those relating more than two models, have received less attention. In this paper, we consider how a multiary consistency relation may be defined in terms of binary consistency relations and how consistency restoration may be carried out on a network of models and relationships between them. In particular, we consider the circumstances under which we can prove non-interference between several bidirectional transformations that impact on the same model and how the use of a more refined notion of consistency can help in cases where this is not possible. In the process, we develop an abstract theory of parts of a model that are read or modified by a bidirectional transformation. We relate the work to megamodelling and discuss further research that is needed.

Abstract Software build systems tackle the problem of building software from sources in a way which is sound (when a build completes successfully, the relations between the generated and source files are as specified) and optimal (only genuinely required rebuilding steps are done). In this paper, we explain and exploit the connection between software build and the megamodel consistency problem. The model-driven development of systems involves multiple models, metamodels and transformations. Transformations—which may be bidirectional—specify, and provide means to enforce, desired “consistency” relationships between models. We can describe the whole configuration using a megamodel. As development proceeds, and various models are modified, we need to be able to restore consistency in the megamodel, so that the consequences of decisions first recorded in one model are appropriately reflected in the others. At the same time, we need to minimise the amount of recomputation needed; in particular, we would like to avoid reapplying a transformation when no relevant changes have occurred in the models it relates. The megamodel consistency problem requires flexibility beyond what is found in conventional software build, because different results are obtained depending on which models are allowed to be modified and on the order and direction of transformation application. In this paper, we propose using an orientation model to make important choices explicit. We show how to extend the formalised build system pluto to provide a means of restoring consistency in a megamodel, that is, in appropriate senses, flexible, sound and optimal.

The model-driven development of systems involves multiple models, metamodels and transformations. Transformations -- which may be bidirectional -- specify, and provide means to enforce, desired "consistency" relationships between models. We can describe the whole configuration using a megamodel. As development proceeds, and various models are modified, we need to be able to restore consistency in the megamodel, so that the consequences of decisions first recorded in one model are appropriately reflected in the others. At the same time, we need to minimise the amount of recomputation needed; in particular, we would like to avoid reapplying a transformation when no relevant changes have occurred in the models it relates. In general, however, different results are obtained depending on which models are allowed to be modified and on the order and direction of transformation application. In this paper we propose using an orientation model to make important choices explicit. We explain the relationship between software build systems and the megamodel consistency problem. We show how to extend the formalised build system pluto to provide a means of restoring consistency in a megamodel that is, in appropriate senses, flexible, sound and optimal.

No abstract available.

The model-driven development of systems involves multiple models, metamodels and transformations, and relationships between them. A bidirectional transformation (bx) is usually defined as a means of maintaining consistency between "two (or more)" models. This includes cases where one model may be generated from one or more others, as well as more complex ("symmetric") cases where models record partially overlapping information. In recent years binary bx, those relating two models, have been extensively studied. Multiary1bx, those relating more than two models, have received less attention. In this paper we consider how a multiary consistency relation may be defined in terms of binary consistency relations, and how consistency restoration may be carried out on a network of models and relationships between them. We relate this to megamodelling and discuss further research that is needed.

Abstract An important use of the Unified Modelling Language (UML) is modelling synchronous object-oriented software systems. State diagrams are used to model interesting object behaviour, including method invocation. However, almost all previous work formalising state diagrams has assumed asynchronous communication. We show that UML’s “run to completion” semantics leads to anomalous behaviour in the synchronous case, and in particular that it is not possible to model recursive calls, in which an object receives a second synchronous message whilst still in the process of reacting to the first. We propose a solution using state diagrams in two complementary ways.

The IEEE/ACM CCSE initiative to propose guidelines for an undergraduate program in software engineering provides an opportunity to rethink the role of software maintenance and evolution in software engineering curricula. The purpose of this panel is to share experiences and discuss novel ways in which evolution and maintenance can be incorporated in an undergraduate software engineering curriculum.

The reengineering of legacy systems --- by which we mean those that have value and yet "significantly resist modification and evolution to meet new and constantly changing business requirements" --- is widely recognised as one of the most significant challenges facing software engineers. The problem is widespread, affecting all kinds of organisations; serious, as failure to reengineer can hamper an organisation's attempts to remain competitive; and persistent, as there seems no reason to be confident that today's new systems are not also tomorrow's legacy systems.This paper argues1. that the main problem is not that the necessary expertise does not exist, but rather, that it is hard for software engineers to become expert;2. that the diversity of the problem domain poses problems for conventional methodological approaches;3. that an approach via systems reengineering patterns can help.We support our contention by means of some candidate patterns drawn from our own experience and published work on reengineering. We discuss the scope of the approach, how work in this area can proceed, and in particular how patterns may be identified and confirmed.