risks along with defining proper metrics to protect the
endangered system and estimating plant states in spite
of attacks (Na, Park, and Eun 2019; Lezoche and
Panetto 2018). Encountering such observations,
brought about another level of attempts to elevate
resiliency of the system: revolving around
characteristics like predictability and diagnosability
which also stood at the high ranks of the FCA double
clustering.
Redundancy and reliability were also the
characteristics that coupled well with resiliency in
FCA and were also discussed closely with the concept
in the literature. As mentioned by (Na, Park, and Eun
2019), redundancy is the principle that can be
advantageous in estimating resiliency in majority of
the systems. On the other hand, the intention of
redundancy in the system can be increasing its
reliability since it relies on employing multi-pronged
solutions rather than a single technique which also
improves the security and resiliency of the system
(Lezoche and Panetto 2018).
In addition to all, stability was also a characteristic
that was paid attention to on reaching safety, security
and consequently the resiliency of the system since
fast reconfiguration of attacks can lead to maintaining
the stability of the system which keeps it safe and
helps it retain normal operation (Potteiger, Zhang,
and Koutsoukos 2020).
7 CONCLUSIONS
The paper presented a study on Cyber Physical
Systems meta-models and their representative
characteristics. To this extent, two main steps were
taken to find out about ‘How are CPS metamodels
described and characterized?’, and ‘How is
Knowledge represented in CPS metamodels?’
through which CPS meta-models were profoundly
investigated regarding what characteristics they are
designed to mirror in the metamodels.
Implementing Formal Concept Analysis (FCA) as
the clustering technique, the most aimed
characteristics in CPS meta-models were studied.
Due to the results, “resiliency” was the dominant
characteristic that was targeted implicitly or explicitly
in the scientific paper. “Fault-Tolerant”,
“diagnosability”, “redundancy” and “safety and
security” were the ones followed resiliency in the list
but with noticeable difference. Implementing the
association rules by the clustering technique has also
confirmed the results and showed that with a
probability of 85% and above, resiliency is the one
characteristic looked for in CPS meta-model,
implicitly or explicitly.
In a sequel, the work makes a contribution in the
concept of Cyber Physical Systems characteristics in
a way that it not only lists the characteristics that has
been studied implicitly or explicitly in meta-model
constructions, it also takes care of the road map to the
most focused characteristic in CPS metamodels.
Thanks to FCA and its association rules, it was
possible to find the hidden relationship between the
characteristics that mainly characterize the CPS meta-
model.
The present work can be an initial point of
development of a CPS-family metamodel. The goal is
to improve the actual metamodel with the dynamic
part and all the inner semantics that is mandatory for
an evolutive and adaptive CPS.
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