[Jot-newsletter] [JOT] JOT Subscriber Newsletter Volume 11, no. 3 ( 2012)

Journal of Object Technology editor at jot.fm
Tue Oct 2 13:57:40 CEST 2012


For Volume 11, no. 3 ( 2012)

I. Letter from the JOT Editor

Dear Readers,

This latest issue consists of two special sections, the first containing four papers on the International Workshop on Model Comparison, and the second containing two papers on the ICOOLPS and MASPEGHI workshops at ECOOP 2010.

Oscar Nierstrasz
Editor-in-Chief, Journal of Object Technology
editor at jot.fm -- http://www.jot.fm

II. Content


International Workshop on Model Comparison.
By Davide Di Ruscio, Dimitris Kolovos

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.



A Solution for Concurrent Versioning of Metamodels and Models.
By Antonio Cicchetti, Federico Ciccozzi, Thomas Leveque

Model-Driven Engineering has been widely recognised as a powerful paradigm for shifting the focus of software development from coding to modelling in order to cope with the rising complexity of modern systems. 
Models become the main artefacts in the development process and therefore undergo evolutions performed in different ways until the final implementation is produced.
Moreover, modelling languages are expected to evolve too and such evolutions have to be taken into account when dealing with model versioning. Since consistency between models and related metamodels is one of the pillars on which model-driven engineering relies, evolution of models and metamodels cannot be considered as independent events in a model versioning system.
This article exploits model comparison and merging mechanisms to provide a solution to the issues related to model versioning when considering metamodel and model manipulations as concurrent and even misaligned. A scenario-based description of the challenges arising from versioning of models is given and a running example is exploited to demonstrate the proposed solutions.


Conflict Visualization for Evolving UML Models.
By Petra Brosch, Martina Seidl, Manuel Wimmer, Gerti Kappel

The urgent demand for supporting teamwork and continuous evolution of
software models triggered intensive research on optimistic
version control systems for models. State-of-the-art model versioning approaches primarily
focus on detecting changes and conflicts between concurrently evolved versions of
a model. However, techniques for conflict visualization have been hardly
investigated yet.
In this paper, we propose to support the visualization of conflicts in the concrete syntax of UML models.
For this purpose, we present an approach to tentatively merge
concurrently evolved versions of one model featuring
all performed changes, yet keeping conformance to the UML metamodel.
Changes and conflicts are visualized in this
tentatively merged model without requiring any editor extensions.
Instead, we employ the powerful profile mechanism of UML to enable modelers to resolve conflicts within their favorite UML editor.


On the Impact Significance of Metamodel Evolution in MDE.
By Ludovico Iovino, Alfonso Pierantonio, Ivano Malavolta

Harnessing metamodels to engineer application domains is at the core of Model-Driven Engineering. A large number of artifacts pursuing a common scope are defined starting from metamodels which represent the nucleus of an ecosystem. Analogously to any software artifact, metamodels are equally prone to evolution. However, changing a metamodel might affect the components of the ecosystem. In fact, when a metamodel undergoes modifications, the related artifacts might require to be consistently adapted in order to recovery their validity. This is an intrinsically difficult process. It requires different techniques for each specific kind of artifact and can easily lead to inconsistencies and irremediable information erosion, if based on spontaneous and individual skills.
This paper discusses the problem of identifying, predicting and evaluating the significance of the metamodel change impact over the existing artifacts. The approach is agnostic of the adaptation technique and formalizes the whole ecosystem and the relatedness of the involved artifacts in terms of megamodels. This allows developers i) to establish relationships between the metamodel and its related artifacts, and ii) to automatically identify those elements within the various artifacts affected by the metamodel changes. The approach can be considered as preparatory to any systematic adaptation process.


Language-Specific Model Versioning Based on Signifiers.
By Philip Langer, Manuel Wimmer, Jeff Gray, Gerti Kappel, Antonio Vallecillo

In model-driven engineering (MDE), models constitute the central artifacts in the development process, and thus, are often built by teams of developers. As a consequence, adequate version control for models is crucial to the success of MDE-based projects. Several model versioning systems have been proposed recently.
Most of them are generic in the sense that they are agnostic to modeling languages. Although this ensures a wide applicability, important merge issues may not be detected.
In this paper, we present an orthogonal extension to generic model versioning systems for enabling the detection of an important subset of language-specific merge issues. Users may enhance the versioning system's capabilities by defining signifiers, which describe the combination of features of a model element type that convey the superior meaning of its instances. Signifiers improve the different phases of the versioning process including comparing and merging models leading to a higher quality of the finally merged models. We showcase the applicability of our approach by enhancing the versioning support for the modeling language Ecore.



ICOOLPS 2010 and MASPEGHI 2010.
By Olivier Zendra, Markku Sakkinen

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.



Efficient Compilation of .NET Programs for Embedded Systems.
By Olivier Sallenave, Roland Ducournau

Compiling under the closed-world assumption (CWA) has been shown to be
an appropriate way for implementing object-oriented languages such as
Java on low-end embedded systems. In this paper, we explore the
implications of using whole program optimizations such as Rapid Type Analysis (RTA) and coloring on
programs targeting the .NET infrastructure. We extended RTA so that it takes
into account .NET specific features such as (i) array covariance, a language feature also supported in Java, (ii) generics, whose specifications in .NET impacts type analysis and (iii) delegates, which encapsulate methods within objects. We also use an intraprocedural control flow analysis in addition to RTA . We evaluated the optimizations that we implemented on programs written in C#. Preliminary results show a noticeable reduction of the code
size, class hierarchy and polymorphism of the programs we optimize. Array covariance is safe in almost all cases, and some delegate calls can be implemented as direct calls.


Towards a full multiple-inheritance virtual machine.
By Roland Ducournau, Flor\'{e}al Morandat

Late binding and subtyping create runtime overhead for object-oriented
languages, especially in the context of both multiple inheritance and
dynamic loading.
Recent experiments show that this overhead is marked with static, non-adaptive
compilers, which work under the open-world assumption.
Therefore, dynamic, i.e. adaptive, compilation might present a solution to this
efficiency issue.
This paper presents the abstract architecture of a virtual machine and a
dynamic compiler for unrestricted multiple-inheritance.
This architecture involves an object representation that allows for shortcuts
in the default implementations,
coupled with compilation/recompilation protocols that maintain the most
efficient implementations compatible with the current state of the program.
The object representation proposed is based on perfect class hashing,
which shortcuts to static calls or the single-subtyping implementation.
Moreover, this article proposes a new methodology, based on random simulation,
for evaluating the runtime efficiency and recompilation cost of the proposed
The resulting experiments show that the architecture proposed should provide
the same runtime efficiency as Java and .NET, thus offsetting most of the
multiple-inheritance overhead.


III. About JOT

The Journal of Object Technology (JOT) is a peer-reviewed, open-access journal dedicated to the timely publication of previously unpublished research articles, surveys, tutorials, and technical notes on all aspects of object technology.

JOT is available online at http://www.jot.fm and is free to both readers and authors, with no registration required.

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