The first edition of GEMOC workshop was co-located with the MODELS 2013 conference in Miami, FL, USA. The workshop provided an open forum for sharing experiences, problems and solutions related to the challenges of using of multiple modeling languages in the development of complex softwarebased systems. During the workshop, concrete language composition artifacts, approaches, and mechanisms were presented and discussed, ideas and opinions exchanged, and constructive feedback provided to authors of accepted papers. A major objective was to encourage collaborations and to start building a community that focused on providing solutions that support what we refer to as the globalization of domain-specific modeling languages, that is, support coordinated use of multiple languages throughout the development of complex systems. This report summarizes the presentations and discussions that took place in the first GEMOC 2013 workshop.
Modern software-intensive systems serve diverse stakeholder groups and thus must address a variety of stakeholder concerns. These concern spaces are often associated with specialized description languages and technologies that are based on concern-specific problem and solution concepts. Software and system engineers are thus faced with the challenging task of integrating the different languages and associated technologies used to produce various artifacts in the different concern spaces.
GEMOC 2013 was a full-day workshop that brought together researchers and practitioners in the modeling languages community to discuss the challenges associated with integrating multiple, heterogeneous modeling languages. Supporting coordinated use ? This workshop is supported by the GEMOC initiative (http://gemoc.org) and the ReMoDD initiative (http://www.cs.colostate.edu/remodd) of modeling languages leads to what we call the globalization of modeling languages. The languages of interest for the participants ranged from requirements to runtime languages, and included both general-purpose and domain-specific languages. Challenges related to engineering composable languages, semantic composition of languages and to reasoning about systems described using heterogeneous languages were discussed
The workshop GEMOC 2013 was co-located with MODELS 2013 in Miami, FL, USA, on September 29th, 2013. In this report we document the various presentations, as well as the enthusiastic and intense discussions that took place during the workshop. The workshop report is organized as follows. Section 2 gives a broad overview of the workshop, including the topics of interest and relevant application domains. Section 3 describes the paper review and selection process, and the structure of the workshop. Section 4 summarizes the presentations made in the first half of the workshop day. Section 5 then presents the main points raised in the discussions that followed the presentations. The intent of the discussions was to position each presented approach in a language and model composition landscape. An initial global landscape was introduced and discussed in the second half of the workshop day. The results of that discussion are summarized in Section 6. Conclusions are drawn in Section 7. 2
Software intensive systems are becoming more and more complex and interconnected. Consequently, the development of such systems requires the integration of many different concerns and skills. These concerns are usually covered by different languages, with specific concepts, technologies and abstraction levels. While the use of multiple languages eases the development of target concerns, it also raises language and technology integration problems at the different stages of the software life cycle. In order to reason about the global system, it becomes necessary to explicitly describe the different kinds of the relationships that can exist between the different languages used in the development of a complex system. To support effective language integration, there is a pressing need to reify and classify these relationships, as well as the language interactions that the relationships enable.
In this context, the workshop attracted submissions that include outlines of language integration approaches and case studies, or that identify and discuss well-defined problems about the management of relationships between heterogeneous modeling languages. The goal was to facilitate discussions among the participants that lead to an initial classification of useful kinds of language relationships and their management.
The Call for Papers explicitly solicited contributions that describe case studies on coordinated use of multiple modeling languages, and/or practical experience, opinions and related approaches. Authors were invited to submit short papers describing (i) their language integration experience, or (ii) novel approaches for integrating modeling languages. Authors were also invited to store full versions of models used to illustrate their novel approach or experience in the Repository for Model Driven Development (ReMoDD). This allowed us to share the actual models with participants and the wider modeling community before, during and after the workshop.
The topics of interest for GEMOC 2013 was: – Composability and interoperability of heterogeneous modeling languages – Language integration challenges, from requirement to design, to analysis and simulation, to runtime. – Model and metamodel composition – Multi-paradigm modeling and simulation
Submissions describing practical and industrial experience related to the use of heterogeneous modeling languages were also encouraged, particularly in the following application domains: – Cyber-Physical Systems, System of Systems – Smart City, Smart Building, Home automation – Complex Adaptive Systems – Internet of Services, Internet of Things 3
Benoit Combemale, Julien Deantoni and Robert B. France organized and chaired the program committee (PC) for this GEMOC edition. The workshop website10 and the call for papers (CfP) was online, quite 6 months before the workshop date. Apart from the workshop website, the CfP was announced on different professional mailing lists (e.g., SEWORLD, pUML, planetmde).
We received 11 submissions and finally accepted 8 papers, resulting in an acceptance rate of 72%. Each submission was reviewed by at least three members of the PC. Papers were selected based on their relevance to the topics for the workshop and the reviews provided by PC members. The organizers are very grateful to PC members for performing this important service to the community and for the quality of their work. The PC consisted of: Walter Cazzola, (DICo, University of Milano, Italy), Benoit Combemale (University of Rennes 1, France), Julien DeAntoni (University of Nice Sophia Antipolis, France), Robert B. France (Colorado State University, USA), Jeff Gray (University of Alabama, USA), Jean-Marc Jézéquel (University of Rennes 1, France), Jörg Kienzle (McGill University, Canada), Marjan Mernik (University of Maribor, Slovenia), Pieter J. Mosterman (MathWorks, USA), Gunter Mussbacher (University of Ottawa, Canada), Bernhard Rumpe (RWTH Aachen University, Germany) and Eugene Syriani (University of Alabama, USA).
The format of the workshop reflected the goals of the workshop: To provide constructive feedback on submitted papers and models on the coordinated use of different modeling languages, and to foster collaborations and community building. The format of the workshop was that of a working meeting. Hence, it was less focused on presentations and more on producing and documenting a research roadmap that identifies challenges, different forms of language integration, and relates existing solutions.
The workshop day was split into two parts. In the first part, an introduction and short presentations of the accepted papers were given. The second part of the day was dedicated to open discussions of the presented contributions and other related topics. We lead the discussion towards a classification of existing and proposed forms of language integration. This workshop report is the result of the beneficial discussions we had. 10 Cf. http://gemoc.org/gemoc2013
The papers and the associated talks are available on the workshop web pages (http:
//www.gemoc.org/gemoc2013). The associated models are available in the ReMoDD
repository (http://www.remodd.org).
[
An important part of the workshop was dedicated to discussions on how to realize the vision of globalized modeling languages. The aim was to map out a landscape of language and model composition issues that reflected ideas raised in the previous presentations and the experiences of workshop participants. To structure the discussions, the organizers proposed to follow the Why? What? Where? How? pattern as reported in the rest of this section. 5.1
Why?
Composition of models is highly desired, because the history of computer science has
shown that development can only be managed by dividing a complex task or
product into smaller easier sub-structures. This in particular holds for models which we
like to decompose along sub-structures of the product, e.g. into components [
When different viewpoints are modeled in different languages, model composition
also becomes language composition, where models of different languages need to
become interoperable. This is necessary for example for the UML, where structural and
behavioral models describe the same system, but also in the recently emerging and
potentially more interesting domain of distributed systems, where several different, but
similar languages are used to describe the behavior of system components [
We can identify four main reasons for using models written using different formalisms: – The decomposition of a complex system into different parts that belong to different technical domains which have their own modeling formalisms and tools; – The change in the level of abstraction during the design of a system, for instance from a non-deterministic automata for specification, to VHDL for the concrete realization; – The need for different models of a system that model different aspects, or offer differents views on the system and therefore use different modeling formalisms: the timing or power consumption model of a system may use a different formalism than the functional model; – The need for different models of a system for different activities during the design process: a model used for code generation and a model used for verification may use different formalisms.
These four reasons lead to four corresponding issues: – How does one compose the structure and behavior of heterogeneous models? – How does one check that a model is a refinement of a more abstract model? – How does one synchronize different views on different aspects of a system? – How does one check the consistency of different models of a given system?
Only if these forms of composition are well understood will we be able to carry out integrated code generations, simulations, validations and verifications on integrated models. These composition issues are rooted in the semantics of the models, with the added complexity of the definition of a mapping between concepts that belong to different semantic domains and are represented according to different syntaxes.
Even though the composition of models and languages is somehow related to the forms of composition for products, we need to be explicitly aware that these are different forms of compositions. That is why it is necessary to explicitly clarify what the composition is about. In particular, it would be very nice if a specification formalism provides a composition operator for its specifications in such a way that this composition conforms to the composition of the specified components.
Identifying the relationships that exists between different languages is useful to
support the understanding of language composition, from a systemic point of view [
Additionally, besides the technical forms of composition, the ability to compose has also an organizational consequence. If we can compose individually developed models, we can decompose the team into smaller sub-teams developing individual parts. This is why composition of models is an important requisite for successful projects developing complex products. 5.2
Formally, composition is an operator taking at least two arguments and producing one
result. Model composition thus involves manipulation of models. Each model has a
syntax and a semantics. Composition can operate on the syntax, for example deriving an
integrated new model describing the information originally contained in both models
[
Furthermore, since models are developed incrementally across the development
lifecycle and at different rates in different sub-teams, requiring models to be complete
before composition can cause project delays. To address this we must also allow for
the meaningful composition of partially complete models [
Relying on an existing classification of existing composition supports the identification of the elements to compose during the process of designing a given composition. One can rely on the existing relations to guide its own development and support incremental approaches. The fact that a language L “implements” concepts modeled by a language L’ implies that both elements (the concept to be implemented in L’ and its associated artefacts in L) exists at the time of the composition, even if developed asynchronously. On the contrary, if L “uses” elements from L’, one cannot use L to work while the model in L’ is not complete.
These considerations hold for any kind of modeling languages, structural or behavioral. However, from a practical point of view, in a top-down approach we develop structure first and thus need decomposition on structure on the higher level. Typically behavioral aspects are only modeled and thus composed on a more fine-grained details level in the later phases of the development. On the other hand, a bottom-up approach involves composing already developed parts of a system to produce a complete system. However, in bottom-up approaches, the composition is usually made at the model level by making interoperable homogeneous interfaces and usually do not address composition of syntactic elements. 5.3
We outlined in the previous section how the composition can operate on different parts
of languages and models. It is also interesting to note that the composition can be
specified and applied at different level: From the language level to some compiled code.
Additionally, the specification of the composition and its application can also be done
at different levels. For instance, a composition operator can be specified between two
languages in order to create a new language [
This also includes their resulting infrastructure, for example, lexer, parser, symbol tables, or editors. For an efficient and agile composition of existing languages, these aspects should be reused as much as possible and only a minimal amount of additional glue-code should be necessary. The level at which the specification and the application of the composition is realized depends on the main objective of the composition (i.e. the why). For instance, because the semantics of a language combination has to be considered, the composition is preferably defined on the language level. However, in a reuse perspective the linkage should take place as late as possible to be able to provide the same language component for different compositions. The idea behind this is the same as for framework or libraries in programming languages which can be used as precompiled components without providing the sources. This speeds up the development process significantly as the libraries do not have to be compiled again and again for every usage while it restrains the possibility of analysis of the composed system. 5.4
How? In order to be able to compose different languages and models without developing the languages for each combination from scratch again or specifying the matching parts for each model combination we need a concise and consistent definition of the interfaces of languages and models. An approach similar to that used in existing programming languages, where methods or classes have an interface for its usage encapsulating the complexity of the actual implementation, may be applicable. If languages provide interfaces that hide their internal complexity, a library of language components could be created allowing the composition of languages by writing a minimal amount of gluecode for each combination.
The need for an interface holds for models as well. Each model should provide an
interface which can be used from other models without knowing the internal details
[
By using such approaches, a composition of languages can be reduced to a mapping between the language concepts needed to combine models along their interfaces. Only if the existing language concepts are not sufficient to define such a mapping, an extension of one or both languages is needed for the composition.
And finally the composition of the language tooling have to be considered. However, if all of these aspects are implemented using clear interfaces, the composition could be derived from the already defined mapping of the language concepts even automatically.
When only partial information is known about a model, techniques such as model
synthesis can be used to construct an approximate, but well-formed, model based on
the known information. Such approximate models can be used as stand-ins for partially
complete models in composition operations [
The various criteria about compositions lead to various implementations. Such
implementations can be hard coded [
The first edition of the workshop met its goals and thus can be considered a success. The discussions that took place during the workshop were of very high quality and provided insights into some of the pressing problems associated with the use multiple modeling languages in development projects. A key result is a deep appreciation by the participants of the need to develop support for globalizing modeling languages. The ongoing research that was reported in the workshop and the discussions that took place are a good indication that community around these problems is emerging. For more information about the GEMOC initiative please visit the following website: http: //gemoc.org. 7
GEMOC 2013 was supported by the GEMOC initiative (cf. http://gemoc.org) that promotes research seeking to develop the necessary breakthroughs in software languages to support global software engineering, i.e., breakthroughs that lead to effective technologies supporting different forms of language integration, including language collaboration, interoperability and composability. Part of this initiative, the workshop was partially supported by the ANR INS project GEMOC (grant #ANR-12-INSE0011).
GEMOC 2013 was also supported by the ReMoDD project, an NSF funded project (award number CNS-1305381).