Purpose – The purpose of this paper is to provide a feature‐based characterization of version control systems (VCSs), providing an overview about the state‐of‐the‐art of versioning systems dedicated to modeling artifacts.Design/methodology/approach – Based on a literature study of existing approaches, a description of the features of versioning systems is established. Special focus is set on three‐way merging which is an integral component of optimistic versioning. This characterization is employed on current model versioning systems, which allows the derivation of challenges in this research area.Findings – The results of the evaluation show that several challenges need to be addressed in future developments of VCSs and merging tools in order to allow the parallel development of model artifacts.Practical implications – Making model‐driven engineering (MDE) a success requires supporting the parallel development of model artifacts as is done nowadays for text‐based artifacts. Therefore, model versioning ca...

A survey on model versioning approaches

IntroductionModel Driven Engineering (MDE) techniques support extensive use of models in order to manage the increasing complexity of software systems. Appropriate abstractions of software system elements can ease reasoning and understanding and thus limit the risk of errors in large systems. Automatic model transformations play a critical role in MDE since they automate complex, tedious, error-prone, and recurrent software development tasks. Airbus uses automatic code synthesis from SCADE models to generate the code for embedded controllers in the Airbus A380. Commercial tools for model transformations exist. Objecteering and Together from Borland are tools that can automatically add design patterns in a UML class model. Esterel Technologies have a tool for automatic code synthesis for safety critical systems.Other examples of transformations are refinement of a design model by adding details pertaining to a particular target platform, refactoring a model by changing its structure to enhance design quality, or reverse engineering code to obtain an abstract model. These software development tasks are critical and thus the model transformations that automate them must be validated.A fault in a transformation can introduce a fault in the transformed model, which if undetected and not removed, can propagate to other models in successive development steps. As a fault propagates across transformations, it becomes more difficult to detect and isolate. Since model transformations are meant to be reused, faults present in them may result in many faulty models.Model transformations constitute a class of programs with unique characteristics that make testing them challenging. The complexity of input and output data, lack of model management tools, and the heterogeneity of transformation languages pose special problems to testers of transformations. In this paper we identify current model transformation characteristics that contribute to the difficulty of systematically testing transformations. We present promising solutions and propose possible ways to overcome these barriers.

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Barriers to systematic model transformation testing

As Model-Driven Engineering (MDE) is increasingly applied to larger and more complex systems, the current generation of modelling and model management technologies are being pushed to their limits in terms of capacity and efficiency. Additional research and development is imperative in order to enable MDE to remain relevant with industrial practice and to continue delivering its widely recognised productivity, quality, and maintainability benefits. Achieving scalability in modelling and MDE involves being able to construct large models and domain-specific languages in a systematic manner, enabling teams of modellers to construct and refine large models in a collaborative manner, advancing the state of the art in model querying and transformations tools so that they can cope with large models (of the scale of millions of model elements), and providing an infrastructure for efficient storage, indexing and retrieval of large models. This paper attempts to provide a research roadmap for these aspects of scalability in MDE and outline directions for work in this emerging research area.

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A research roadmap towards achieving scalability in model driven engineering

The paper presents WebGME, a novel, web- and cloud-based, collaborative, scalable (meta)modeling tool that supports the design of Domain Specific Modeling Languages (DSML) and the creation of cor- responding domain models. The unique prototypical inheritance, origi- nally introduced by GME, is extended in WebGME to fuse metamodel- ing with modeling. The tool also introduces novel ways to model cross- cutting concerns. These concepts are especially useful for multi-paradigm modeling. The main design drivers for WebGME have been scalability, extensibility and version control. The web-based architecture and the constraints the browser-based environment introduces provided signif- icant challenges that WebGME has overcome with balanced trade-os. The paper describes the architecture of WebGME, argues why the major design decisions were taken and presents the novel features of the tool.

/pdf/next-generation-meta-modeling-web-and-cloud-based-2ch19pic3g.pdf

Next Generation (Meta)Modeling: Web- and Cloud-based Collaborative Tool Infrastructure

This survey paper presents the current state of model comparison as it applies to Model-Driven Engineering. We look specifically at how model matching is accomplished, the application of the approaches, and the types of models that approaches are intended to work with. Our paper also indicates future trends and directions. We find that many of the latest model comparison techniques are geared towards facilitating arbitrary meta models and use similarity-based matching. Thus far, model versioning is the most prevalent application of model comparison. Recently, however, work on comparison for versioning has begun to stagnate, giving way to other applications. Lastly, there is wide variance among the tools in the amount of user effort required to perform model comparison, as some require more effort to facilitate more generality and expressive power.

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A Survey of Model Comparison Approaches and Applications

For a widespread success of the model-driven paradigm, appropriate tools such as "Version Control Systems" (VCS) allowing for consistency maintenance between concurrently edited model versions are required to adequately support a model-based development process. Initial attempts for graph-based versioning of model artifacts are either tightly coupled to the modeling environment, not flexible with respect to the used modeling language or cannot interpret the model's semantics. On basis of those characteristics, the goal of the outlined thesis presented in this paper is to provide mechanisms to detect conflicting modifications between parallel edited model versions more accurately. By reducing falsely indicated conflicts and by finding additional semantic conflicts, the resolution process can be simplified by means of appropriate techniques for comparison, conflict detection, conflict resolution and merge.

/pdf/models-in-conflict-towards-a-semantically-enhanced-version-59rwh5i1q7.pdf

Models in Conflict --- Towards a Semantically Enhanced Version Control System for Models

In collaborative software development, the utilization of Version Control Systems VCSs is a must. For this, a multitude of pessimistic as well as optimistic VCSs for model artifacts emerged. Pessimistic approaches follow the lock-edit-unlock paradigm whereas optimistic approaches allow parallel editing of one resource, which are therefore the preferred ones. To be flexible for the ever increasing variety of modeling environments and languages such tools should be independent of the modeling environment and applicable to various modeling languages. Those VCS characteristics may implicate a lack of information for the conflict detection method by virtue of firstly receiving solely the state of an artifact without concrete editing operations and secondly due to unavailable knowledge about the semantics of a modeling language. However, in optimistic VCSs concurrent changes can result in conflicts and inconsistencies. In environment and language independent VCSs inconsistencies would even arise more often due to information losses. Hence, accurate conflict detection methods are indispensable for the realization of such VCSs. To tackle this task, the "Semantically enhanced Model Version Control System" SMoVer is presented. With SMoVer it is possible to specify the semantics of a modeling language, needed for conflict detection in order to provide more accurate conflict reports than other current environment and language independent VCSs. In this work, it is exemplified how semantics of a specific modeling language can be specified in SMoVer, how those specifications can improve the accuracy of conflict reports and finally how those can be presented to modelers.

Semantics for Accurate Conflict Detection in SMoVer: Specification, Detection and Presentation by Example

To make the model-driven paradigm a widespread success, appropriate tools such as version control systems (VCS) are required to adequately support a model-based development process. However, first approaches specializing on model-based versioning, do not take into account the semantics of the artefacts they operate upon. Thus, conflict detection mechanisms are based on detecting conflicting concurrent modifications on a software artefacts syntactic representation, only, without explicitly considering the semantics the artefact stands for. As opposed to a heavyweight approach relying on formal mathematics, we follow a lightweight approach that is based on creating views of a model that explicate a certain aspect of a modeling language’s semantics. Such a view is created through a model transformation from the original model edited by the developers. Using both the original model and the created view our approach relies on graph-based comparison strategies to detect conflicts due to concurrent editing to determine socalled syntactic and semantic conflicts, respectively. Consequently, by means of various example scenarios, we demonstrate how our approach is able detect conflicts that otherwise would remain undetected.

http://www.schwinger.at/PUBLICATIONS/18_2007_MDEIS___ModelsInConflict_Detection_of_Semantic_Conflicts_in_ModelBased_Development.pdf

Models in Conflict – Detection of Semantic Conflicts in Model-based Development

Accessibility for graphics in web applications is still not only a shortcoming for visually impaired people but may also be a request of people with other special needs. In the Access2Graphicsproject SVG (Scalable Vector Graphics) is used to dynamically generate graphics that are adapted to the user's individual requirements in order to make them accessible for each user. Beside the users also the graphics designer (provider) need support to be able to offer accessible graphics. The focus of this paper therefore mainly is on introducing the analysis as well as the verification component of Access2Graphics. Both, reuse of existing graphics and verification with respect to defined guidelines should make the generation process of graphics more efficient regarding the development time and quality.

Kerstin Altmanninger

Papers

A survey on model versioning approaches

Models in Conflict --- Towards a Semantically Enhanced Version Control System for Models

Semantics for Accurate Conflict Detection in SMoVer: Specification, Detection and Presentation by Example

Models in Conflict – Detection of Semantic Conflicts in Model-based Development

Accessible Graphics in Web Applications: Dynamic Generation, Analysis and Verification