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https://ceur-ws.org/Vol-2019/multi_intro.pdf
Preface to the 4th International Workshop
on Multi‐Level Modelling (MULTI 2017)
Tony Clark
Sheffield Hallam University, UK
Ulrich Frank
University of Duisburg-Essen, Germany
Manuel Wimmer
TU Wien, Austria
number of participants was around 20. MULTI 2015 also
I. INTRODUCTION spawned a new Wiki for the multi-level modeling research
Traditional approaches to modelling systems tend to community:
emphasize two-levels: type and instance. Recently, the benefits http://homepages.ecs.vuw.ac.nz/Groups/MultiLevelModeling/
of meta-level access have been argued to be of importance in
terms of language definition, particularly in terms of domain-
specific languages. The ability to define elements at the meta- The scope of the MULTI workshops includes the following
level improves the scope for abstraction, reuse, and ultimately topics:
system quality. Providing meta-level access introduces a
1. The exact nature of elements in a multi-level hierarchy
number of methodological and technological challenges: how,
and whether, to introduce strict separation between levels; how and how best to represent them.
to express the relationships between elements at different 2. The importance and role of potency and its variants
levels; technologies for expressing multi-level concepts. such a durability and mutability.
3. The structure and labeling of a multi-level modelling
The roots of multi-level modelling can be traced back over framework.
15 years to when the first papers on flaws in the OMG’s four 4. Methods and technique for discovering clabjects,
level modelling architecture were published. From these roots, specializations and classification relationships.
various flavours of multi-level modelling have emerged over
5. Formal approaches to multi-level modelling.
time, many with associated supporting tools. Examples include
DPF workbench, GModel, Melanee, MetaDepth, Nivel, 6. Experiences and challenges in providing tool support
OMME and XModeller. Although these technologies share for multi-level modelling.
many common ideas, there are significant differences in the 7. Experiences and challenges in applying multi-level
fundamental principles they use to support multi-level modelling techniques to large and/or real world
modelling. As a result, the current tool landscape is highly problems.
fragmented with different tools designed to serve very different 8. Model management languages (transformation, code
purposes. There is also a lack of common multi-level generation etc.) in a multi-level setting.
modelling guidelines, educational material and even 9. Criteria and approaches for comparing multi-level
terminology. Without a common foundation and an evidence- modelling approaches.
base for case studies on the benefits of multi-level modeling, 10. Integration of modelling and programming languages.
particularly in industry, it will be difficult for the approach to
evolve beyond the currently active research community. II. PAPERS
The MULTI series of workshops aims to provide a forum MULTI 2017 attracted 14 submissions and accepted 8 as
for advances in the field to be presented and discussed. The full papers and an additional poster. The papers covered a wide
first MULTI workshop (www.miso.es/multi/2014/) was held at spectrum of topics related to the multi-level modelling,
MODELS 2014 in Valencia and spawned a special theme issue demonstrating that the field is active and has significant
of SoSyM. The second (www.miso.es/multi/2015/) and third applicability. The workshop introduced the MULTI challenge
MULTI workshops were held at MODELS 2015 in Ottawa and (described below) and included a presentation addressing its
at MODELS 2016 in St. Malo respectively. The average issues.
A configuration is a physical artifact that is composed of components. A component may be composed of other components or
of basic parts. There is a difference between the type of a component and its instances. A component has a weight. A bicycle is
built of components like frame, a handle bar, two wheels, etc. A bicycle component is a component. A frame, a fork, a wheel,
etc. are bicycle components. Frames and forks exist in various colors. Every frame has a unique serial number. Front wheel and
rear wheel must have the same size. Each bicycle has a purchase price and a sales price. There are different types of bicycles for
different purposes such as race, mountains, city, etc. A mountain bike or a city bike may have a suspension. A mountain bike
makes have a rear suspension. That is not the case for city bikes. A racing fork does not have a suspension. It does not have a
mud mount either. A racing bike is not suited for tough terrains. A racing bike is suited for races. It can be used in cities, too.
Racing frames are specified by top tube, down tube, and seat tube length. A racing bike can be certified by the UCI. A racing
frame is made of steel, aluminum, or carbon. A pro race bike is certified by the UCI. A pro race frame is made of aluminum or
carbon. A pro racing bike has a minimum weight of 5200 gr. A carbon frame type allows for carbon or aluminum wheel types
only. “Challenger A2-XL” is a pro-racer for tall cyclists. The regular sales price is 4999.00. Some exemplars are sold for a
lower price. It is equipped with a Rocket-A1-XL pro race frame. The Rocket-A1-XL has a weight of 920.0 gr. A sales manager
may be interested in the average sales price of all exemplars of a certain model and may also be interested in the average sales
price of all mountain bikes, all racing bikes etc.
Figure 1: The MULTI Challenge (2017)
A key problem faced by the MULTI community is one that Urbán and Theisz who propose a modular approach that offers
arises from the variety of approaches and definitions for a validation framework.
concepts and relationships. The paper Developing an
Ontological Sandbox: Investigating Multi-Level Modelling’s Multi-level modelling offers the potential for increased
Possible Metaphysical Structures by Partridge, de Cesare, abstraction and reuse when representing data. Such abstraction
Mitchell, Gailly and Khan addresses this issue by proposing a is key when aiming to achieve data integration through the
structure within which definitions can be constructed and definition of new language features whose property constraints
analyzed. apply across type levels. The paper Applying Multi-Level
Modeling to Data Integration in Product Line Engineering by
System engineering tooling is an area that is highly Nesic and Nyberg describes how power-types can be used in
appropriate for the application of multi-level modelling since product-lines to succinctly capture constraints such as
tools must manage type-level information as data while at the disjointness and completeness.
same time allowing tool-users to manipulate tool data as types.
The benefits of the approach together with a proof of concept Working with multi-level models poses an interesting
implementation is investigated in the context of model-based challenge since there is no agreed approach to visually present
user interface development in the paper A Multi-level Approach and manipulate the many different type levels and their
for Model-Based User Interface Development by Bjorn Benner. relationships. The paper An Example Application of a Multi-
In addition, tooling must offer a range of user functionality that Level Concrete Syntax Specification with Copy-and-Complete
is an extension of that supported by traditional tools, Semantics by Jens Gulden describes the application of a new
addressing issues such as: what happens to models and their language (the Topology Type Language) to this problem in
instances when type-levels are changed. The paper terms of the step-by-step construction of a multi-level model.
Maintenance of Multi-Level Models – An Analysis of The field of multi-level modelling has recently expanded to
Elementary Change Operations by Toepel and Benner presents produce several approaches and technologies. Some address
a framework within which multi-level model change different problem domains as described by the papers in this
functionality can be defined and studied. workshop; some agree on key features and others take
Programming languages have provided meta-level features opposing views. There is a need to provide a way of evaluating
since the early days of Lisp and Smalltalk. Lisp has run-time the application of multi-level approaches as described in the
types and a self-defined interpreter. Smalltalk has meta-classes. paper On Evaluating Multi-Level Modeling by Atkinson and
More recent languages, such as Java, have a reflective library Kühne.
to inspect the program at run-time. However, the motivation in The poster Extending a UML and OCL Tool for Multi-
most cases relates to implementation issues rather than Levels: Applications towards Model Quality Assessment by
modelling. The paper DeepRuby: Extending Ruby with Dual Doan and Gogolla shows how the USE tool can be extended to
Deep Instantiation by Neumayr, Schuetz, Horner and Schrefl support multi-level modelling.
shows how principled multilevel modelling can be
implemented in the Ruby programming language. III. MULTI CHALLENGE
Multi-level modelling introduces the notion of user-defined Multi-level modelling is an active field with potential to
types together with the constraints that classify the instances of provide significant improvements to system engineering.
the type. The question of how to check the user-defined type However, it is a challenging area and to date the multi-level
constraints is addressed by the paper Validated Multi-Layer community has tended to focus on technology issues making
Meta-modeling via Intrinsically Modeled Operations by Mezei, the benefits difficult to appreciate for those outside the field.
The MULTI 2017 organizers proposed and presented a
challenge based on a real-word scenario, and invited
researchers to use the challenge as the basis of concrete
contributions that can be used to raise the profile of the field.
The challenge was discussed at the workshop whose delegates
agreed to refine the details for MULTI 2018 with the aim of
attracting as many contributions as possible. The 2017 version
of the challenge is shown in figure 1. The challenge is intended
as the basis for any multi-level modelling approach providing
that concrete benefits can be demonstrated.
Multi-level features of any submission to the challenge may
include any of the following: knowledge about the domain
should be represented at the highest level possible; the model
can be a foundation for a software system suited for a wide
range of general bicycle stores including specialization to, for
example, a dealer of professional racing bikes; associations and
constraints should cross levels where appropriate; the integrity
of lower levels of the model should be consistent with any
changes applied to higher levels; mechanisms should
synchronize MLM-based models with code.
The following are examples of application-level features of any
submission to the challenge: multi-level modelling can be used
as a basis for configuration for example every bicycle type
except for racing bikes may be equipped with an electric motor
and electric bikes need enforced brakes and a battery; as a
basis for advanced business analytics, for example find every
bicycle type that has an electric motor and that has the least
number of sales in 2017; representing business processes in
multi-level models, for example order management, such as
Customer, Order; addressing behaviour abstraction within
multi-level models, for example most dealerships favour their
own type of order management process, a multi-level model of
an order management process should support the reuse of
common aspects of order management and extend/refine them
to satisfy particular requirements; generating a bicycle product
management system from a multi-level model that uses
models@run-time to support the addition of new types of
bicycle.
The challenge is used as the basis of exemplifying multi-
modelling using MultEcore as demonstrated in the MULTI
2017 paper Multilevel Modelling with MultEcore: A
Contribution to the MULTI 2017 Challenge by Macías, Rutle
and Stolz.