The common good

Filed under: Editorial — Laurence Tratt @ 13:37

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!


Extreme Modeling 2012 Special Edition

Filed under: Editorial — Laurence Tratt @ 14:27

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)


The Song Remains (Almost) The Same

Filed under: Editorial — Laurence Tratt @ 11:47

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!


TOOLS Europe 2012 Special Section

Filed under: Editorial — Jan Vitek @ 10:40

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.


Changing of the guard

Filed under: Editorial — Jan Vitek @ 04:04
The Journal of Object Technology is the only open access academic publication dedicated to object-orientation in all its forms. Objects have been with me for my entire scientific career, it is thus an honor to take over from outgoing editor in chief Oscar Nierstrasz.  My goal  as the next editor of JOT is first and foremost to continue on the path blazed by Oscar, strengthening the scientific quality and increasing the readership of JOT.  One challenge that a journal like JOT faces is to find its proper place in the changing landscape of scientific publishing. Why should authors submit to JOT rather than to a conference or to another journal? Unlike most conferences, journals allow a dialogue between authors and reviewers, one that leads to improved papers rather than simple binary decisions. As to why JOT, I believe that our editorial board is unique in its composition and ensures that papers on topics related to object technology will receive some the best and most helpful expert reviews from world-renowned experts who share a passion for objects.

Jan Vitek


Farewell editorial

Filed under: Editorial — Oscar Nierstrasz @ 11:41

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

Lies, Damned Lies and UML2Java

Filed under: Column — richpaige @ 11:40

We review far too many research papers for journals and conferences. (Admittedly, we probably write too many papers as well, but that’s another story.) We regularly encounter misunderstandings, misconceptions, misrepresentations and plain old-fashioned errors related to Model-Driven Engineering (MDE): what it is, how it works, what it really means, what’s wrong with it, and why it’s yet another overhyped, oversold, overheated idea. Some of these misunderstandings are annoyingly common for us to want to put them down on the digital page and try to address them here. Perhaps this will help improve research papers, or it will make reviewing easier; perhaps it will lead to debate and argument; perhaps this list will be consigned to an e-bin somewhere.

Our modest list of the ten leading misconceptions — which is of course incomplete — is as follows.

1. MDE = UML

At least once a year we read an article or blog post or paper that assumes that MDE is equivalent to using UML for some kind of systems engineering. This is both incorrect and monotonously boring. The reality is that MDE neither depends on, or implies the use of UML: the engineering tasks that you carry out with MDE can be supported by any modelling language that (a) has a metamodel/grammar/well-defined structure; and (b) has automated tools that allow the construction and manipulation of models. Using UML does not mean you are doing MDE — you might be drawing UML diagrams as rough sketches, or to enable simulation/analysis, or for conceptual modelling. Doing MDE does not mean you must be using UML: you could be using your own awesome domain-specific languages, or another general-purpose language that has nothing to do with UML.

We have noticed that this misunderstanding appears less frequently today than it did five years ago; perhaps the message is slowly getting through. The misunderstandings might have started because of the way in which we often introduce MDE to students: conceptual or design modelling with UML is often the first kind of modelling that students see.

So, the good news is that if you’re doing MDE, you don’t have to use UML; and if you are using UML, you don’t have to do MDE. The bad news is that there are many other misconceptions out there waiting to pounce. We are just getting started.

2. MDE = UML2Java

Code generation is often the first use case that’s thought of, mentioned, dissected and criticised in any technical debate about MDE. “You can generate code from your models!” is the cry of the tool vendor. This is usually followed by the even more thrilling: “you can generate Java code from your UML models!” As exciting a prospect as this is, the overemphasis of code generation in discussions of MDE has led to the myth of the UML-to-Java transformation, and that it is the sole way of doing MDE. Without doubt, this is a legitimate MDE scenario that has been applied successfully many times. But as we mentioned earlier, you do not have to use UML to do MDE. Similarly, you don’t have to target Java via code generation to do MDE. Indeed, there is a veritable medley of programming languages you can choose! C#, Objective-C, Delphi, C++, Visual Basic, Cobol, Haskell, Smalltalk. All of these exciting languages can be targeted from your modelling languages using code generators.

It would be much more interesting to read about MDE scenarios that don’t involve the infamous UML2Java transformation — there are undoubtedly countless good examples that are out there. It’s always helpful to have a standard example that everyone can understand, but eventually a field of research has to move beyond the standard, trivial examples to something more sophisticated that pushes the capabilities of the tools and theories.

3. MDE ⇒ code generation

But what if you don’t care about code generation? Clearly you are a twisted individual: if you’re doing MDE you must be generating code, right? Wrong! Code generation — a specific type of model-to-text transformation — from (UML, DSML) models is just another legitimate MDE scenario. Code may not be a desirable visible output from your engineering process. You may be interested in constructing and assessing the models themselves — producing a textual output may not deliver any value to you. You may be interested in generating text from your models, but not executable code (e.g., HTML reports, input to verification tools). You may be interested in serialising your models so as to persist them in a database or repository.

However, if you are generating code from models, you are probably applying a form of MDE (the nuance is really whether your models have a precisely defined structure [metamodel] and whether or not your code generators are externalised — and can be reused).

4. MDE ⇒ transformation.

We’ve established that MDE is more than code generation. MDE is also about more than transformation.

Some problems cannot be easily solved with transformation. As advocates of MDE do we pack our bags and look for furrows that we can plough with model transformation techniques? Or can MDE still be of use?

Supporting decision making — helping stakeholders to reason about trade-offs between competing and equally attractive solutions to a problem — is an area in which models and MDE are increasingly used. (See the wonderful world of enterprise architecture modelling for examples). Code, software or computer systems are not necessarily central to these domains, and transformation does little more for us than produce a nicely formatted report. Instead, we need to consider exploiting other state-of-the-art software engineering techniques alongside typical MDE fare. Perhaps search-based software engineering (i.e. describing what a solution looks like) is preferable to model transformation (i.e. describing how an ideal solution is constructed) in some cases. We have done work in this area at our university [DOI: 10.1007/978-3-642-31491-9_32], and there is growing interest in this topic.

Transformation is powerful. Refactoring, merging, weaving, code generating and many other exciting verb-ings would not be possible without transformation theory and tools. However, models are ripe for other types of analysis and decision support and for these tasks, transformation is often not the right approach. In 2003 model transformation was characterised as the heart-and-soul of MDE. In 2013 we believe that a more well-rounded view is preferable.

5. “The MDE process is inflexible.”

This was an actual quote from a paper we once had to review for a conference. It was both a strange sentence and an interesting one, because we didn’t know what it meant. Just what is “the MDE process”? Did we miss the fanfare associated with its announcement? Arguably “process” and MDE are orthogonal: if you are constructing well-defined models (with metamodels) and using automated tools to manipulate your models (e.g., for code generation) then you are carrying out MDE; the process via which you construct your models and metamodels and manipulate your models is largely independent. You could apply the spiral model, or V-model, or waterfall. You could embed, within one of these processes, the platform-independent/platform-specific style of development inherent in approaches like Model-Driven Architecture (MDA). There is no MDE process, but by carrying out MDE you are likely to follow a process, which may or may not be made explicit.

6. MDE = MOF/Ecore/EMF

You must conform to the Eclipse world. Or the OMG world. You must define your models and metamodels with MOF or Ecore. You will be assimilated.

This is, of course, nonsense. MOF and Ecore are perfectly lovely and useful metamodelling technologies that have served numerous organisations well. But there are other perfectly lovely and useful metamodelling technologies that work equally well, such as GOPRR, or MetaDepth, or even (shock horror) pure XML. Arguably, the humble spreadsheet is the most widely used and most intuitive metamodelling tool in the world.

MDE has nothing to do with how you encode your models and metamodels; it has everything to do with what you do with them (manipulate them using automated tools; build them with stakeholders). Arguably, you should be able to do MDE without worrying about how your models are encoded — a principle that we have taken to heart in the Epsilon toolset that we have developed at our university.

7. Model transformation = Refinement

Refinement is a well-studied notion in formal methods of software engineering: starting from an abstract specification, you successively “transform” your specification into a more concrete one that is still semantics-preserving. In some formal methods, the transformations that you apply are taken from a catalogue of so-called refinement rules (which provably preserve semantics). Their application ultimately results in a specification that is semantically equivalent to an executable program. The refinement process thus produces a program that is “correct-by-construction”.

You can follow the logical (mis-)deduction behind this misconception quite easily:

  • Refinement rules transform specifications.
  • Specifications are models (see earlier misconceptions).
  • Model transformations are a set of transformation rules.
  • Transformation rules transform models.
  • Therefore, refinement rules are transformation rules.
  • Therefore, refinement is transformation.

This is actually OK. Refinement is a perfectly legitimate form of model transformation. The problem is with the reverse inference, i.e., that a transformation rule is a refinement rule. If you assume that transformations must be semantics preserving, then this is not an unreasonable conclusion to draw. But model transformations need not preserve semantics.

Heretical statements like this usually generate one of several possible responses:

  • “This is crazy: why would I want to transform a model (which I have lovingly crafted and bestowed with valid properties and attributes) into something that is manifestly different, where information is lost?”
  • “OK, I can see that you might write a transformation that does not preserve semantics, but they must be dangerous, so we just need to be able to identify them and isolate them so that they never get deployed in the wild.”
  • “I don’t have to preserve semantics? That’s a relief! Semantics preserving transformations are a pain to construct anyway!”

These responses are all variants of misunderstandings we have seen previously: this idea that MDE is equated to a specific scenario or instance of application.

The first misunderstanding is, of course, confusing a specific category of model transformation — those that preserve semantics — with all model transformations. What are some examples of non-semantics preserving transformations? They are legion: measurement applied to UML diagrams is a classic example, where we transform a UML diagram into a number. The transformation process calculates some kind of (probably object-oriented) metric. Another example is from model migration: updating a model because its metamodel has changed. In some scenarios, a metamodel changes by deleting constructs; the model migration transformation likely needs to delete all instances of those constructs. This is clearly not semantics preserving.

The second misunderstanding is the classical “Well, you can do it but don’t expect me to like it” response. Unfortunately, in many real model transformation scenarios, you have to break semantics, and you probably need to enjoy it too. Consider a transformation scenario where we want to transform a very large model (e.g., consisting of several hundred thousand elements) conforming to a very large metamodel (like MARTE, AUTOSAR, SysML etc) into another very large model conforming to a different very large metamodel. Because we are good software engineers, we are likely to want to break this probably very large and complicated transformation problem into a number of smaller ones (see, for example, Jim Cordy’s excellent keynote at GPCE/SLE 2009 in Denver), which then need to be chained together. Each of the individual (smaller) transformations need not preserve semantics — indeed, some of the transformations may be to intermediate convenience languages that exist solely to make complex processing easier.

8. MDE can’t possibly work for real systems engineering because it doesn’t work well in complex domains where there is domain uncertainty.

In systems engineering we often have to cope with domain uncertainty — we don’t fully understand the threats and risks associated with a domain until we have got a certain way along the path towards developing a system. If there is domain uncertainty then the modelling languages that have been chosen, and the operations that we apply to our models (e.g., transformations, model differencing, mergings) are liable to change, and this becomes expensive and time-consuming to deal with. Domain uncertainty is a real problem — for any systems engineering technique, whether it is model-based, code-based or otherwise. Domain uncertainty will always lead to change in systems engineering. The question is: does MDE make handling the change associated with domain uncertainty any worse? Perhaps it does. If you’re using domain-specific modelling languages, then changes will often result in modifications to your modelling languages (and thereafter corresponding changes to your model transformations, constraints etc). If you are using code throughout development, changes due to domain uncertainty will be reflected in changes to your architecture, detailed modular design, protocols, algorithms, etc. Arguably, these are problems of similar conceptual complexity — it’s hard to see how MDE makes things worse, or indeed better: it’s an essentially hard problem of system engineering.

9. Metamodels never change

As we saw in the first misconception, MDE is not only about UML, but also about defining and using other modelling languages. However, when we (or you, or the OMG) design a modelling language, even a small one, we rarely get it right the first time. Or the fifth time. Or the ninth time. Like all forms of domain modelling, constructing a metamodel is difficult and requires consideration of many trade-offs. Language evolution is the norm, not the exception.

Despite this, we often encounter work that:

  • Does not consider or discuss tradeoffs made in language design. These kinds of papers often leave us wondering why a domain was modelled in a particular way (e.g. “why model X as a class, and Y as an association?” “why model with classes and associations at all?”).
  • Presents the product of language design, but not the process itself. How was the language designed? Did it arrive fully formed in the brain of a developer, or were their interesting stories and lessons to be learnt about its construction?
  • Proposes standardisation of domain X because “there is a metamodel.” A metamodel is often necessary for standardisation, it is not sufficient. (For example, does your favourite transformation language implement all of the QVT specification? We bet it doesn’t — and shame on you, of course!)
  • Contributes extensions to — or changes to — existing languages with little regard for the impact of these changes on models, transformations or other artefacts. Even in UML specifications, the impact of language evolution is not made apparent: there are no clear migration paths from one version to another, as we discovered at the 2010 Transformation Tool Contest (see also the forum discussion on UML migration).

Misconceptions about language evolution might stem from the way in which we typically go about defining a modelling language with contemporary MDE tools. We normally begin by defining a metamodel/grammar, then construct models that use (conform to) that metamodel/grammar, and then write model transformations or other model management operations. The linearity in this workflow is reminiscent of Big Design Up Front, and evokes painful memories of waterfall processes for software development.

However, we have found that designing a modelling language — like many other software engineering activities — is often best achieved in an iterative and incremental manner. We are not alone in this observation. Several recent modelling and MDE workshops (XM, ME, FlexiTools) have included work on inferring metamodels/grammars from example models; relaxing the conformance relationship (typing) of metamodels; and propagating metamodel changes to models automatically and semi-automatically. These are promising first steps towards introducing incrementality and flexibility into our domain-specific modelling tools, but the underlying issue is rather more systematic. As a community, we need to acknowledge that changing metamodels are the norm, and to better prepare to embrace change.

10. Modelling ≠ Programming

There is a tendency in many papers that we read to put a brick wall between modelling and programming — to treat them as conceptually different things that can only be bridged via transformations (created by these magical wizards, or transformation engineers). We’ve seen this type of thing before, in the 1980s, with programming and specification languages in formal methods. Some specification languages like Z were perfectly useful for specifying and reasoning, but were difficult to use for transition to code. Wide-spectrum languages, that unified programs and specifications in one linguistic framework (e.g., Carroll Morgan’s specification statements, Eric Hehner’s predicative programming, Ralph Back’s refinement calculus), did not have these difficulties. Treating models and programs in a unified framework — as artefacts that enable system engineering — would seem to have conceptual and technical benefits, and would allow us to have fewer academic arguments about their differences (and more arguments down at the pub).

Well, we lied when we said there were only ten misconceptions.

11. MDE = MDA

We end with a real chestnut: that MDE is the same thing as MDA.

MDA first appeared via the OMG back in 2001. It is a set of standards — including MOF, CWM and UML — as well as a particular approach to systems development, where business and application logic are separated from platform technology — the infamous PIM/PSM separation. MDE is more general than MDA: it does not require use of MOF, UML or CWM, nor for platform-specific and platform-independent logic and concerns to be kept separate. MDE does require the construction, manipulation and management of well-defined and structured models — but you don’t have to make use of OMG standards, or a particular style of development to do it.

So, for you authors out there: when you say that you have an MDA-based approach, please be sure that you really mean it. Are you using MOF and UML? Are you reliant on a PIM/PSM separation? If so, great! Carry on! If not, please think again, and prevent us from complaining loudly and publicly on Twitter.

The End

We have to stop somewhere. These are just a few of the misconceptions, myths, and misunderstandings related to MDE we’ve encountered. Do send us your own!

About the Authors

Richard Paige is a professor at the University of York, and complains bitterly about everything MDE on Twitter (@richpaige). He also likes really bad films. His website is http://www.cs.york.ac.uk/~paige

Louis Rose (@louismrose) is a lecturer at the University of York. He wrangles Java into the Epsilon MDE platform, tortures undergraduate students with tales of enterprise architecture, and is regularly defeated at chess. His research interests include software evolution, MDE and — in collaboration with Richard — evaluating the effects of caffeine on unsuspecting research students. His website is http://www.cs.york.ac.uk/~louis


ICOOLPS 2010 and MASPEGHI 2010 Special Section

Filed under: Special Section Editorial — markku @ 13:46

At ECOOP 2010 in Maribor, Slovenia, the two workshops MASPEGHI (MechAnisms for SPEcialization, Generalization and inHerItance) and ICOOOLPS (Implementation, Compilation, Optimization of Object-Oriented Languages, Programs and Systems) were combined because both were rather small and shared common concerns, their topic areas being strongly related. Six papers had been accepted to MASPEGHI, but only five were presented because the authors of one paper could not attend the conference and workshop. Three papers had been accepted to ICOOOLPS, and all were also presented.

The workshop authors were later asked to submit extended versions of their papers for possible publication in this special section. We received two extended papers from ICOOOLPS and one from MASPEGHI. They were carefully reviewed by three reviewers each, and then revised by the authors according to the reviewers’ comments. In our opinion, all revised papers were interesting, of high quality and significantly extended from the workshop versions. One of them, however, needed more work from its authors, and they could not complete it within a reasonable time. As a consequence, only two extended, reviewed and revised papers are now published in this special section.

Olivier Zendra (for ICOOOLPS),
Markku Sakkinen (for MASPEGHI)

International Workshop on Model Comparison Special Section

Filed under: Special Section Editorial — Tags: — ddr @ 13:46

This JOT special section contains three extended and peer reviewed papers obtained from the first and second editions of the International Workshop on Model Comparison in Practice (IWMCP), and an additional paper selected outside the contributions of the workshop. The first edition of IWMCP was held on July 1st, 2010 in Malaga, Spain, whereas the second edition was held on May 30, 2011 in Prague, Czech Republic. Both have been organized as satellite events of the TOOLS Europe conference.

Model Driven Engineering elevates models to first class artefacts of the software development process. To facilitate multi-user collaboration and enable version management and seamless evolution of models and metamodels, support for robust and performant model comparison and differencing mechanisms is essential. Previous research has demonstrated that mechanisms used for comparison and differencing of text-based artefacts (e.g. source code) are not sufficient for comparing models, as they are unaware of the structure and the semantics of the compared artefacts.

To date, several model-specific model comparison approaches have been proposed, each demonstrating different characteristics and focusing on particular sub-problems. For instance, model comparison techniques have been adopted for software refactoring, for transformation testing, to support the coupled evolution of metamodel and models, or to analyse existing artefacts with respect to some criteria. However the consensus is that this research area is still young and more research is required in order to achieve the full potential of model comparison.

The goal of IWMCP has been to bring together both researchers in the area of model comparison and differencing to report novel results, and adopters of existing approaches to present their experiences and provide insights on issues encountered when applying these approaches in practice.

In the first paper of this special section, Antonio Cicchetti, Federico Ciccozzi, and Thomas Leveque present an approach to support the concurrent versioning of metamodels and models. The proposed techniques exploit model comparison and merging mechanisms to provide a solution to issues related to concurrent and even misaligned evolution of both metamodels and models. In the second paper, Petra Brosch, Martina Seidl, Manuel Wimmer and Gerti Kappel propose the means to visualize and merge conflicts between concurrently evolved versions of a UML model. The profile mechanism of UML is leveraged to enable modelers to resolve conflicts within the used UML editor. In the third paper, Ludovico Iovino, Alfonso Pierantonio, and Ivano Malavolta deal with the problem of coupled evolution of metamodels and related artifacts. In particular, the authors propose an approach to i) establish relationships between the domain metamodel and its related artifacts, and ii) automatically identify those elements within the various artifacts affected by the metamodel changes. In the fourth paper, Philip Langer, Manuel Wimmer, Jeff Gray, Gerti Kappel, and Antonio Vallecillo propose the adoption of signifiers to enhance the different phases of the versioning process including comparing and merging models. In particular, signifiers are applied to specify the natural identifier of a model element to eliminate the issues related to the adoption of approaches based on artificial universally unique identifiers (UUIDs).

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
Dimitris Kolovos, University of York


ICMT 2011 Special Section

Filed under: Special Section Editorial — Tags: — jordicabot @ 11:37

This JOT special section contains two carefully selected papers from the fourth edition of The International Conference on Model Transformation (ICMT 2011) held on June 27–28, 2011 in Zürich, Switzerland.

Modelling is a key element in reducing the complexity of software systems during their development and maintenance. Model transformations are essential for elevating models from documentation elements to first-class artifacts of the development process. Model transformation includes model-to-text transformation to generate code from models, text-to-model transformations to parse textual representations to model representations, model extraction to derive higher-level models from legacy code, and model-to-model transformations to normalize, weave, optimize, and refactor models, as well as to translate between modeling languages.

Model transformation encompasses a variety of technical spaces, including modelware, grammarware, and XML-ware, a variety of transformation representations including graphs, trees, and DAGs, and a variety of transformation paradigms including rule-based graph transformation, term rewriting, and implementations in general-purpose programming languages.

The study of model transformation includes foundations, semantics, structuring mechanisms, and properties (such as modularity, composability, and parameterization) of transformations, transformation languages, techniques and tools. An important goal of the field is the development of high-level declarative model transformation languages, providing model representations of transformations that are amenable to ‘higher-order’ model transformation. To achieve impact on software engineering practice, tools and methodologies to integrate model transformation into existing development environments and processes are required.

ICMT is the premier forum for the presentation of contributions that advance the state-of-the-art in the field of model transformation and aims to bring together researchers from all areas of model transformation.

The 2011 edition of the conference received 62 abstracts, of which 51 materialized as full papers, and 14 were eventually selected — a 27% acceptance rate. Each submission was reviewed by at least 3 program committee members and on average by 4 program committee members. One of the submitted papers was also submitted to TOOLS Europe 2011 and was rejected by both conferences without reviews. Three papers were first conditionally accepted and subjected to a review of the revision taking into account reviewer comments. The program also includes an invited talk and paper by Alexander Egyed, who unfolded his research agenda for smart assistance in interactive model transformation.

In the first paper of this special section, Wimmer et al. present a framework for the classification of model-to-model transformation languages according to the rule-inheritance mechanisms they implement, covering both syntactic and semantics aspects. The framework is used to classify three prominent transformation languages: ATL, ETL and a forthcoming implementation of TGGs atop MOFLON. In the second paper, Jesús Sánchez Cuadrado, Esther Guerra and Juan De Lara outline how model transformations can be made generic, so that the same transformation can be used in a number of distinct instances. The particular mechanism allows a transformation to be associated to a number of meta-models, and for transformations to be effected for all the instances of such a meta-model.

We thank the people who made this special section possible. Most importantly, we thank the referees for giving of their time to thoroughly and thoughtfully review and re-review papers, and to the authors who put such hard work into the several revisions from conference submission to journal acceptance.

Jordi Cabot
Eelco Visser

August 2012

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