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      <title-group>
        <article-title>Summary of the 12th International Workshop on Models@run.time</article-title>
      </title-group>
      <contrib-group>
        <contrib contrib-type="author">
          <string-name>Sebastian G o¨tz</string-name>
          <email>sebastian.goetz@acm.org</email>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Nelly Bencomoy</string-name>
          <email>nelly@acm.org</email>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Kirstie Bellmannz</string-name>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Gordon Blairx</string-name>
          <email>gordon@comp.lancs.ac.uk</email>
        </contrib>
      </contrib-group>
      <abstract>
        <p>-This year the 12th edition of the workshop Models@run.time was held at the 20th International Conference on Model Driven Engineering Languages and Systems. The workshop took place in the city of Austin, Texas, USA, on the 18th of September 2017. The workshop was organized by Sebastian Go¨tz, Nelly Bencomo, Kirstie Bellman and Gordon Blair. Here, we present a summary of the workshop and a synopsis of the topics discussed and highlighted during the workshop.</p>
      </abstract>
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    <sec id="sec-1">
      <title>I. INTRODUCTION</title>
      <p>
        Once more, the models@run.time community [
        <xref ref-type="bibr" rid="ref2">2</xref>
        ], [
        <xref ref-type="bibr" rid="ref3">3</xref>
        ], [
        <xref ref-type="bibr" rid="ref5">5</xref>
        ]
has met at the MODELS conference and discussed the newest
early stage research in our field. Compared with previous
editions of workshops in MODELS, in general, the number of
submissions dropped and it included our workshop. Notably,
this did not have any impact on the number of participants at
the workshop which was quiet high again. Although this year,
only 4 papers were accepted for presentation at the workshop,
we had approximately 20 active participants throughout the
day and lots of lively discussions. Table I and Figure 1 show
how the workshop quantitatively evolved over the last years.
      </p>
      <p>Accepted (Long+Short)
6+6
4+2
4+6
4+2
11
7+2
5
8
7
4</p>
    </sec>
    <sec id="sec-2">
      <title>II. WORKSHOP SESSIONS</title>
      <p>
        Among the participants, there were many new researchers –
an observation we regularly have over the last years. Hence, we
started the workshop with an introduction to models@run.time
in three parts. First, Nelly Bencomo gave a historical
perspective on the last 12 years of models@run.time based on [
        <xref ref-type="bibr" rid="ref1">1</xref>
        ].
After, Sebastian Go¨tz showed first results from an upcoming
literature survey on models@run.time covering 271 papers
from the field. Finally, Kirstie Bellman rounded up the
introduction by teasing challenging problems to be solved in the
60
50
40
30
20
10
0
2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018
      </p>
      <p>Attendees Submissions Accepted</p>
      <p>Fig. 1. The MRT Workshop Series since 2008
future by the community. After this introduction, two sessions
with paper presentations followed. The last session was used
for an intensive discussion of what the community considers
as challenging problems to be solved. In the following, all four
sessions will be summarized in more detail.</p>
      <p>The first session covering presentations by the authors
focused on the application of models@run.time with the purpose
to support software evolution.</p>
      <p>Hassan Gomaa gave the first talk, presenting his paper,
which was jointly authored with Emad Albassam, with the
topic “Run-time Software Architectural Models for Adaptation,
Recovery and Evolution’’. He presented an overview of
architectural runtime models and their use for adaptation recovery
as well as evolution.</p>
      <p>The second talk was given by Dhaminda Abeywickrama,
who presented his paper, jointly authored with Eila Ovaska,
with the topic “Reflexive and Evolutional Digital Service
Ecosystems with Models at Runtime”. In contrast to the
first paper, his approach applied models@run.time at three
abstraction levels: at the level of goals, of architecture and
of the domain/context. The approach was evaluated using a
case study from the ambient assisted living domain.</p>
      <p>The second session covering paper presentations had
assurance as its theme.</p>
      <p>Byron Devries gave the first presentation on his paper,
jointly authored with Betty Cheng, having the title “Using
Models at Run Time to Detect Incomplete and Inconsistent
Requirements”. He presented an approach to detect
incomplete requirements at runtime. Thus, this approach applied
models@run.time at the abstraction level of requirements. The
approach was evaluated using a case study from adaptive
cruise control.</p>
      <p>The second talk was given by Christopher Landauer on
his paper entitled “Active System Integrity Fences”. Fences, as
introduced by Christopher Landauer, are a generalized concept
of contract-based programming, i.e., the application of
modelbased contracts at system runtime. The approach was evaluated
argumentatively in the context of safety-critical systems.
C. Beyond Models@run.time</p>
      <p>Several issues were discussed during the last 60 minutes of
the workshop.</p>
      <p>One issue discussed was the need for a definition of
models@run.time-based architectural patterns, which was
coined by Peter Clarke. The idea is to take advantage of the
experience of the construction of different architectures during
more than a decade and to categorise the different experiences
by using patterns. By this, we could start discussing
models@run.time with the software architecture community.</p>
      <p>There was also discussion about using the notion of
transactions to support the causal connection needed to fully support
runtime models. The need to do further research on the use
of machine learning techniques for emerging runtime models
was also part of the lively discussion. Finally, Kirstie Bellman
introduced the idea of using runtime models for V&amp;V at
runtime.</p>
      <p>In the end, the audience agreed that it is a good idea to run
the workshop again in 2018.</p>
    </sec>
    <sec id="sec-3">
      <title>III. CONCLUSION</title>
      <p>The twelfth edition of the international workshop on
models@run.time was again very well visited (20 participants).</p>
      <p>The trend of submissions was low in comparison to the last
years. Notably, although only few papers were submitted (5),
as a set they presented high quality, which allowed us to accept
four (4) papers.</p>
      <p>One of the defining characteristics of the MRT workshop
is a commitment to discussion time and this year’s workshop
continued that tradition in a lively and informative fashion.
In order to develop high quality models for use at runtime,
we need to deal with the classical AI knowledge engineering
problem of how to get the knowledge that is in an experts
head OR in the systems sensors and status databases into the
models. One of the challenges going forward is to capture the
knowledge that is meaningful to the tasks and the decisions of
the system; this requires a great deal of flexibility and
metaknowledge in the reasoning processes.</p>
      <p>Another topic that was widely discussed was the need
for self-explanation so that the human users and developers
could better monitor when and how the different runtime
models were being used. This was noted as being especially
important when the system has crashed and has switched to
new configurations, and for assessing the progress towards new
goals. In a separate discussion, there was a great deal of
interest by the workshop participants in the growing literature
review, comparison, and gap analysis being done on 271
papers on Models@run.time by Go¨tz and Bencomo. This led
to a great deal of discussion on how to characterize the diverse
findings and what to do with the information gained from the
study and especially how to encourage filling in the research
gapsby the community.</p>
      <p>Branching off from this discussion,we also discussed how
to integrate multiple runtime models.</p>
      <p>We ended the workshop with a discussion of some of the
overarching challenges and problems for MRT.</p>
      <p>This included technical challenges and social challenges for
identifying and bringing in the expertise we need into the
community. Among the technical challenges, one keychallenge was
to better define and support the relationship between design
time and MRT systems for long-term improvement, analysis,
and system understanding. Another was the importance of
discovery processes for the ability to find the relevant MRT
models for a given goal, especially in distributed systems.
The third major challenge was how to share results (including
how to gauge their relevancy) among different MRT models
in distributed, complex systems.</p>
      <p>Among the social issues, we discussed how to encourage the
community to develop more theoretical foundations for such
difficult MRT issues as integration, self-modeling, and model
generation. We also discussed what kinds of new expertise we
need in the community to better address MRT challenges.</p>
      <p>
        Since the first edition of the workshop, it was constantly
co-located to the MODELS conference and, consequently,
mainly attracted participants from the modelling community.
However, this year for the second time we also ran a separate
edition of models@run.time at ICAC [
        <xref ref-type="bibr" rid="ref4">4</xref>
        ] to attract people
from self-aware and autonomous computing. We plan to
continue both editions next year, i.e., a third workshop on
models@run.time for self-aware computing systems at ICAC
and a 13th workshop on models@run.time at MODELS.
      </p>
    </sec>
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