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This JOT special section contains three extended and peer reviewed papers from the first and second editions of the International Workshop on Verification Of modeL Transformation (VOLT). The first edition of VOLT was held on April 21st, 2012 in Montreal, Canada as satellite event of the 5th International Conference on Software Testing, Verification and Validation (ICST 2012). The second edition was held on June 17th, 2013 in Budapest, Hungary as a satellite event of Federated Conferences on Software Technologies: Applications and Foundations (STAF 2013).

Model transformations are everywhere in software development, implicitly or explicitly. They became first-class citizens with the advent of Model-Driven Engineering (MDE). Despite some recent activity in the field, the work on the verification of model transformations remains scattered and a clear perspective on the subject is still not in sight. Moreover, current model transformation tools often lack verification techniques to support such activities. The goal of VOLT is to offer researchers a dedicated forum to classify, discuss, propose, and advance verification techniques dedicated to model transformations. VOLT promotes discussions between theoreticians and practitioners from academy and industry. A significant part of the workshop editions includes a forum for discussing practical applications of model transformations and their verification, including interesting properties to verify and efficient techniques to actually compute those properties.

For this special section, we selected three papers by means of at least two rounds of reviews. All papers were refereed by four well-known experts in the field. The selected papers are the following:

• Moussa Amrani, Benoit Combemale, Levi Lucio, Gehan Selim, Juergen Dingel, Yves Le Traon, Hans Vangheluwe and James Cordy in their paper entitled “Formal Verification Techniques for Model Transformations: A Tridimensional Classification” discuss the evolution, trends, and current practices in model transformation verification found in the literature from three viewpoints: the transformations, their properties, and the verification techniques.
• David Lindecker, Gabor Simko, Tihamer Levendovszky, István Madari and Janos Sztipanovits in their paper entitled “Validating Transformations for Semantic Anchoring” present a technique to validate that a domain-specific language satisfies the intentions that the designer had in mind when engineering the language. The approach consists of validating the consistency between a formalization of intention of a language designer and the semantic mapping of the language, the latter being expressed as a formal model transformation.
• Rick Salay, Marsha Chechik, Michalis Famelis and Jan Gorzny in their paper entitled “A Methodology for Verifying Refinements of Partial Models” present a technique to verify how uncertainty present in models and transformations is reduced after refining models and model transformations.

We would like to thank everyone who has made this special section possible. In particular, we are obliged to all past VOLT organizers, to the reviewers for giving off their time to thoroughly and thoughtfully review papers multiple times, to the authors for contributing to VOLT and JOT with high quality papers, and to the JOT editorial board for making this special issue possible.

Eugene Syriani, University of Montreal (Canada)
Manuel Wimmer, Vienna University of Technology (Austria)

We asked. You said. We listened.

From this issue onwards, all JOT articles will be licensed under a Creative Commons licence. Currently, authors can choose either Attribution 4.0 International (CC BY 4.0) or Attribution-NoDerivatives 4.0 International (CC BY-ND 4.0) as their paper’s license (depending on feedback, we may extend these options over time). The author instructions have been updated accordingly.

In doing this, we’re giving back rights to authors and stating explicitly: JOT is on your side. Practically speaking, this move will make authors’ lives easier, and ultimately that of readers. We hope you enjoy the result!

This JOT special section contains four extended and peer reviewed papers from the first edition of the Extreme Modeling Workshop (XM2012) held on October 1st, 2012 in Innsbruck, Austria as satellite event of the 15th International Conference on Model Driven Engineering Languages & Systems (MODELS2012).

The goal of XM 2012 was to bring together both researchers in the area of modeling and model management in order to discuss more disciplined techniques and engineering tools to support flexibility in several forms in a wide range of modeling activities, including metamodel, model, and model transformation definition processes. The workshop aimed at a) better identifying the difficulties in the current practices of MDE related to the lack of flexibility and b) soliciting contributions of ideas, concepts, and techniques also from other areas of software engineering, such as that of specific language communities (e.g. the Smalltalk and Haskell communities, and the dynamic languages community). These contributions could be useful to revise certain fundamental concepts of Model Driven Engineering (MDE), such as the conformance relation.

From 8 initial submissions we selected 4 papers by means of at least two rounds of reviews. All papers were refereed by three well-known experts in the fields. The selected papers are the following:

• Vadim Zaytsev in his paper entitled Negotiated Grammar Evolution presents a study about the adaptability of metamodel transformations. In particular, some metamodel transformation paradigms, like unidirectional programmable grammar transformation, are rather rigid. They are written to work with one input grammar, and are not easily adapted if the grammar changes. In the paper, the author proposes a solution able to entail isolation of the applicability assertions into a component separate from the rest of the transformation engine, and enhancing the simple accept-and-proceed vs reject-and-halt scheme into one that proposes a list of valid alternative arguments and allows the other transformation participant to choose from it and negotiate the intended level of adaptability and robustness.
• Paola Gómez, Mario Sánchez, Héctor Florez and Jorge Villalobos in their paper entitled An approach to the co-creation of models and metamodels in Enterprise Architecture Projects discuss the problems related to the lack of dynamicity of model editors and the impossibility to load new metamodels at runtime. In the paper, they present an approach able to address such problems by separating ontological and linguistic aspects of metamodels. The GraCoT tool is an implementation of the approach based on GMF and it is also discussed in the paper.
• Konstantinos Barmpis and Dimitrios S. Kolovos in their paper entitled Evaluation of Contemporary Graph Databases for Efficient Persistence of Large-Scale Models compare the commonly used persistence mechanisms in MDE with novel approaches such as the use of graph-based NoSQL databases. Prototype integrations of Neo4J and OrientDB with EMF are used to compare with relational database, XMI and document-based NoSQL database persistence mechanisms. The paper benchmarks also two approaches for querying models persisted in graph databases to measure and compare their relative performance in terms of memory usage and execution time.
• Zoe Zarwin, Marija Bjekovic, Jean-Marie Favre, Jean-Sébastien Sottet, and Henderik A. Proper in their paper entitled Natural Modelling motivate the need for instruments that enable a wider adoption of modeling technologies. To this end it is necessary that such technologies are perceived as natural as possible. After having defined the natural modeling concept, the authors discuss how human aspects of modeling could be better instrumented in the future by using modern technologies.

We would like to thank everyone who has made this special section possible. In particular, we are obliged to the referees for giving off their time to thoroughly and thoughtfully review and re-review papers, to the authors for their hard work on several revisions of their papers, from workshop submission to journal acceptance, and to the JOT editorial board for organising this special issue.

Davide Di Ruscio, University of L’Aquila (Italy)
Alfonso Pierantonio, University of L’Aquila (Italy)
Juan de Lara, Universidad Autónoma de Madrid (Spain)

For me, taking over as Editor-in-Chief of JOT is no small matter. The most recent editors — Oscar Nierstrasz and Jan Vitek — have done sterling work in establishing JOT as a well-read reference for substantial computing research, a job that Bertrand Meyer and Richard Wiener began before them. JOT continues to fill an important role in computing: an open-access journal with rigorous standards. In most senses, my job is to strive to continue Oscar and Jan’s sterling work. After all, when the JOT formula isn’t broken, why break it?

Of course, no such formula can be perfect, because the world around us changes: habits change, needs change, and attitudes change. It is the latter aspect which I wish to address in this, my first editorial. Research, at its best, is intended to benefit mankind: when, instead, it is hidden behind paywalls, its purpose is obstructed. JOT is therefore an open-access journal: whoever you are, whatever your status is, wherever you are in the world, you can read the research we publish in JOT without hindrance.

But JOT has one vestige shared with traditional journals: when authors publish their research in JOT we ask them to transfer the copyright of their paper over to us. What this means is that JOT is then the legal guardian of the paper: anyone who wishes to distribute or alter it — even the original authors — has to ask JOT for permission to do so. This was done with the aim of ensuring that JOT maintained the definitive home of the research and JOT has the legal right to prevent people duplicating (or, worse, plagiarising) the research we publish.

Attitudes in recent years have shifted. Authors want to publish copies of their papers on the homepages, in university paper repositories, and other online paper repositories. It is reasonable for them to ask why, if they put in the effort to perform and write-up the research, they should lose the legal right to post copies of their paper where they wish to.

In consultation with the JOT Steering Committee, I therefore believe that JOT should move to a world where we no longer require authors to transfer copyright to us. There are several possible models for how we might go about this, and we are opening up this discussion to the JOT community, seeding it with an initial proposal. With luck, we will put the new process into place later in the (northern hemisphere) summer.

Our initial proposal is as follows, based in part on the approach taken by similar journals such as PLOSOne and LMCS. Instead of requiring authors to transfer copyright to us, we propose that authors whose papers have passed JOT’s peer-review process are required to place their papers under a Creative Commons license before their paper will be published. Doing so will give everyone — including JOT — the right to host copies of their paper. We intend giving authors the freedom to choose between between the Attribution CC BY or Attribution-NoDerivs CC BY-ND licenses. Broadly speaking, the former would allow anyone to distribute (possibly altered versions of) the paper; the latter would allow anyone to distribute, but not alter, a paper. In both cases, the right to distribute the specific version of the paper accepted by JOT is irrevocable: it will be publicly available for all time. We would request that all copies the authors place on other sites use the JOT template so that JOT is properly credited as the publication that put the effort into reviewing and publishing the paper, but this will rely on author’s goodwill, rather than any legal mechanism.

Please feel free to leave your suggestions in the comments below or by contacting me directly. I would like whatever process we come up with to be as good as it can be, and that is most likely to happen when the JOT community puts its collective brain to the task!

Carlo A. Furia  and   Sebastian Nanz

The 50th International Conference on Objects, Models, Components, Patterns (TOOLS Europe 2012) was the closing event in a series of symposia devoted to object technology and its applications. The conference program included 24 paper presentations covering a broad range of topics, from programming languages to models and development practices. This variety, typical of the TOOLS conferences, is a sign of the vast success of object technology and of its theoretical underpinnings.

This Special Section of the Journal of Object Technology (JOT) consists of the extended versions of two contributions selected among those presented at TOOLS Europe 2012. We picked these two pieces of work among those receiving the most positive reviews before the conference, raising substantial interest at the conference, and passing the muster of additional thorough refereeing for this Special Section after the conference. Besides being mature and high-quality research work in their own right, the two papers target topics that are indicative of the vitality of object technology even now that it has become commonplace.

Lilis and Savidis’s paper “An Integrated Approach to Source Level Debugging and Compile Error Reporting in Metaprograms” discusses techniques and tools to improve the readability and understandability of error reporting with metaprograms — that is, programs that generate other programs, such as the template programming constructs available in C++. Their solution is capable of tracing errors along the complete sequence of compilation stages and also targets aspects of IDE integration. It is also fully implemented and available for download: note the demonstration video linked to at the end of the article.

Wernli, Lungu, and Nierstrasz’s paper “Incremental Dynamic Updates with First-class Contexts” tackles a difficult problem frequently present in complex software systems that must be highly available: how to reduce the downtime required to perform system updates. Their solution hinges on turning contexts into first-class entities. Their Theseus system is thus capable of performing updates incrementally, with different threads running in parallel on different versions of the same class. The conference version of this paper also won the TOOLS 2012 Best Paper Award sponsored by the European Association for Programming Languages and Systems (EAPLS).

We are glad to be able to offer such an interesting Special Section to readers of JOT. We thank Antonio Vallecillo for suggesting this Special Section. We thank the anonymous referees for their punctual and dedicated work, instrumental in guaranteeing high quality presentations; and we thank the authors for choosing TOOLS Europe and JOT to present some of their most interesting research work.

Jan Vitek

It is my great pleasure to welcome Jan Vitek as incoming Editor-in-Chief of JOT. Jan is a long-time contributor to the object-oriented community and is well known for his research in various aspects of programming languages and software engineering, more specifically in the areas of dynamic languages, mobile computation, transactional memory and embedded systems.

It has been nearly three years since Bertrand Meyer invited me to take over as Editor-in-Chief from Richard Wiener, who had done an amazing job of building up JOT’s readership and providing a steady flow of provocative articles on a variety of topics.
There have been mainly two kinds of changes to JOT since then. The first is visible to readers: JOT has a new look, with the web site being driven largely by meta-data. This makes it much easier to keep the web site up-to-date and consistent, and makes it easier to add new features. The second set of changes are visible to authors: the review process is formalized and more rigorous. Despite the added rigor, the review process is very competitive with other journals, with accepted papers typically appearing within six months to a year of initial submission.

In order to make this work, JOT relies on a dedicated team of associate editors (listed in the Masthead), and a large pool of anonymous reviewers who contribute their time to carefully reviewing submissions. In addition to regular articles, JOT has a strong tradition of publishing special issues and special sections of revised, selected papers from workshops and conferences related to object technology. These are prepared by invited editors, usually the PC Chairs of the original event. Finally there is nothing to review if there is not a steady stream of submissions. I would therefore like to sincerely thank all the authors, anonymous reviewers and associate and invited editors who contributed to JOT over the past three years!

Finally, I would like to offer my best wishes to Jan Vitek and encourage him to explore new ways for JOT to serve the OO community.

Oscar Nierstrasz
2013-01-25

JOT is continuing with its policy of publishing issues as soon as new material is available. With this issue we have two regular papers: “DeepFJig — Modular composition of nested classes”, and “A Catalogue of Refactorings for Model-to-Model Transformations”, and we have two special sections, one with selected and expanded papers of ICMT 2011 (international Conference on Model Transformation, Guest editors: Jordi Cabot and Eelco Visser), and a second with selected and expanded papers from RefTest 2010 (Refactoring and Testing Workshop, Guest editors: Steve Counsell and Stephen Swift).

There is a healthy pipeline of submitted papers. 35 regular papers have been submitted so far this year (compared with a total of 60 last year, not counting special sections). 6 regular papers are currently in review, and another 3 are undergoing revision.

Several more special issues are currently in the works, in particular, one on IWMCP 2011 (Guest editors: Dimitris Kolovos and Davide Di Ruscio), and another on TOOLS Europe 2012 (Guest editors: Sebastian Nanz and Carlo Furia). Antonio Vallecillo, the Special Section editor is currently negotiating further sepcial sections, and would be glad to hear from you concerning further proposals.

Oscar Nierstrasz
August 2012

In 2011, JOT experimented with a new, single-issue format, in which articles and special sections were published immediately upon acceptance of the final version. This scheme had the advantage that authors and readers did not have to wait for a backlog of previously scheduled issues before a paper would be published. The disadvantage is that it is harder to see when new material is published, since there is a new “issue” only once a year.

With this issue, JOT is reverting to a format with multiple issues throughout the year, however we will continue to publish new material “as soon as possible”. In practice this means that new articles will appear either in a current, open issue, or in the next scheduled issue. We plan to target four regular issues a year, and two to four further special issues dedicated to special topics.

Publishing material “as soon as possible” means that JOT will keep no backlog of papers for future issues. The risk for JOT is that an empty pipeline may lead to delays in publishing an issue. The advantage for the community is timely publication of new papers. As always, we call on you to submit previously unpublished research articles, surveys, tutorials, and technical notes on all aspects of object technology.