=Paper=
{{Paper
|id=Vol-2326/paper4
|storemode=property
|title=Domain Model for Cyber-Physical Systems
|pdfUrl=https://ceur-ws.org/Vol-2326/paper4.pdf
|volume=Vol-2326
|authors=Asma Djouad,Fadila Atil,Abdelhak-Djamel Seriai,Chahrazed Beddiar
|dblpUrl=https://dblp.org/rec/conf/icaase/DjouadASB18
}}
==Domain Model for Cyber-Physical Systems==
https://ceur-ws.org/Vol-2326/paper4.pdf
Domain Model for Cyber-Physical Systems
Asma Djouad, Fadila Atil, Abdelhak-Djamel Chahrazed Beddiar,
LISCO, LISCO, Seriai LISCO,
Department of Department of LIRMM, Department of
Computer Science, Compute Science, University of Computer Science,
Badji Mokhtar Badji Mokhtar Montpellier/CNRS Badji Mokhtar
University Annaba University Annaba seriai@lirmm.fr University Annaba
asma.djouad@univ- atil_fadila@yahoo.fr Chahrazed.beddiar@gmail.
annaba.org com
Abstract and integrated by a computing and
communication core [Raj10]. This integration of
Cyber Physical systems refer to new class of computation with physical processes in CPS is about
systems that features the integration of intersection, not the union of the physical and the cyber
computation, communications and control [Lee17]. Currently, a precursor generation of CPS can
technologies. The processing elements be found in areas as diverse as aerospace,
coordinate and communicate with sensors and manufacturing, civil infrastructure, chemical processes,
actuators to monitor and affect the entities in healthcare, energy, transportation, and automotive.
the physical world. In this paper, we propose a Designing cyber-physical systems is a
domain model for CPS that tries to bring a challenge originating from the multidisciplinary and
clear terminology, by providing a common heterogeneous nature of integrated components,
lexicon and taxonomy of the CPS domain. networks and types of processed data. In addition
This model describes the most important to the use of more advanced technologies for
concepts in regards to the CPS and the sensors and actuators, and wireless
relationship between these concepts, in order communication, which make CPS applications
is defining a modeling language aims at harder to model, harder to design, and harder to
providing a means of communications analyze than homogeneous systems[Lee17].
between stakeholders in the engineering Consequently, a suitable application development
process. abstraction is required to enable experts from
Keywords: Cyber-physical systems, Domain various domains to specify CPS applications
model, heterogeneous systems. in their fields, and define with ease the rich
interactions between the large numbers of
1 Introduction dissimilar devices. This will be accomplished by
establishing a common grounding and a common
During the recent decades, the rapid advances language for CPS architectures and CPS systems.
in digital computing and communication The first step towards this at that point is to
technologies, has led the development of construct a suitable description logic that provides
advanced sensors, data acquisition system, a common lexicon and taxonomy of the CPS
wireless communication devices and distributed domain, and also to allow scientific discourse
computing solutions. Such technologies are among researchers, system programmers, as well as
integrated into a new system called Cyber- non- technical stakeholders.
physical System (CPS), a harmony of physical The main purpose of this research is to
dynamical systems with the cyberspace. propose a domain model for CPS to
Cyber-physical systems (CPS) have gained a lot generate a common understanding of the
of attention in recent years and are considered components and concepts that constitute them,
as an emerging technology [Haq14]. They are and to expose the CPS specific functionalities
physical and engineered systems whose to domain experts. This model includes a definition
operations are monitored, coordinated, controlled of the main abstract concepts, their
responsibilities and their relationships, on which
Copyright © by the paper’s authors. Copying permitted only for private
and academic purposes.
CPS architectures can be built.
In: Proceedings of the 3rd Edition of the International Conference on
Advanced Aspects of Software Engineering (ICAASE18), Constantine,
Algeria, 1,2-December-2018, published at http://ceur-ws.org
International Conference on Advanced Aspects of Software Engineering
ICAASE, December, 01-02, 2018 Page 34
Domain Model for Cyber-Physical Systems ICAASE'2018
The goal of this paper is to define a modeling Some other propose that represents a congruence of
language aims at providing a means of technologies in embedded systems, distributed systems,
communications between stakeholders in the dependable systems, and real-time systems with
enginnering process. advances in energy-efficient networking,
Besides of the reasons mentioned above, a microcontrollers, sensors and actuators [Raj10].
domain model enables modularity in design, which Cyber-physical systems link between cyber and
the system can be divided into subsystems that physical worlds. The cyber components coordinate and
can be created independently. Thus, it helps communicate to affect the physical processes usually
in development process, since the functions of each with feedback loops where physical processes affect
component are well-known. computations and vice versa [Lee17].
The paper is organized as follows. Section 2 The coordination between cybernetic world and
provides an overview of cyber-physical system, physical world by connecting with human through
includes its definitions and principals’ computation, communication and control is a key factor
characteristics. Section 3 presents our main for future technological developments that changes
contribution which consists of domain model that future computational facilities in all areas including
describes the concepts relevant of cyber-physical business, science, defense, and healthcare with
systems. Finally, section 4 concludes this paper and unprecedented capabilities [Bah11].
provides insight for future work.
2 General Overview of CPS
This section gives an overview of CPS systems. We
present key concepts and components, as well as the
characteristics of CPS.
2.1 Definitions
CPS was identified as a key research area in
2008 by the National Science Foundation (NSF) of
the United States and was ranked as the number one
research priority by the Council of Advisers on Science
and Technology [Lee14].
What is CPS? - The term cyber-physical systems
(CPS) can be viewed as a new generation of systems Figure 1: CPS capabilities
with tight combination between computational and
physical capabilities that can interact with humans What is not CPS?- A CPS is not the computer in
through many new modalities [Bah11]. general (PC), traditional embedded system, and also
The term CPS also refers to distributed not networked control systems (NCS). CPS can be
heterogeneous systems that conducts feedback control regarded as networked embedded systems.
on widely distributed embedded computing systems Wireless sensor network (WSN), internet of things
with organic integration and in-depth collaboration of (IoT) are different from CPS.
computation, communications and control technology IoT is generally considered as interconnecting
(see Figure 1),subject to the theory and technology of internet information sensing devices like wireless
existing network systems and physical systems [Liu17]. sensor and radio frequency through hierarchical
Also a complex CPSs definition was provided by communication infrastructure, while CPS stress the
Shankar Sastry from University of California, Berkeley cooperation between physical procedures and
in 2008: “A cyber-physical system (CPS) integrates computational elements.
computing, communication and storage capabilities WSN is a network formed by a large number of
with monitoring and/or control of entities in the sensor nodes which collaborate together using ad hoc
physical world, and must do so dependably, safely, network technologies to achieve a well-defined purpose
securely, efficiently and real-time”. of supervision of some area, some physical process, etc.
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Domain Model for Cyber-Physical Systems ICAASE'2018
Rather than focusing on the identification of entity, •Networked: cyber-physical systems components are
WSN just senses the signal, and not necessarily typically networked at multiple and extreme scale. The
distinguishes the particular one from numerous entities advanced connectivity is needed for various subsystems
being sensed. It underscores the perception of to coordinate with each other and to ensure real-time
information using data collection, processing and data acquisition from the physical world and
routing functionalities. CPS not just has the capacity of information feedback from the cyber space.
sensing the physical world, yet in addition has solid •Autonomy: CPS can provide high degrees of
capacity to control. Its computational capacity automation, and the control loops must close.
requirement for computing devices far exceeded that of Typically, CPS is a closed loop system, where sensors
IOT and WSN [6]. make measurements of physical dynamics. These
CPS forms a new type of system which deeply measurements are processed in the cyber subsystems,
integrates the ability of computing, communication and which then drive actuators and applications that affect
control. In other terms, CPS is a method of the physical processes.
understanding and designing real world. [Gua16]
CPS Examples- CPSs range from tiny systems such 3 The CPS Domain Model
as pacemaker: which is a small electronic system that
can sense physiological data to assist monitor and The general idea of a CPS is to collect sensory data
control the heart in maintaining regular rhythm, to (measuring properties of the physical world) from a
large-scale systems such as power grid: an electricity variety of sources, convert it to information in the
supply network which includes computer intelligence cybernetic world, process it, understand it, and then
and networking abilities to control the production and notify the physical systems about the findings, and
distribution of electricity. sometimes send control commands to make appropriate
actions back in the physical world or reconfigure
2.2 Characteristics
system parameters if required [Sim15] and [Ala17] (see
Since CPSs are characterized by a large number of figure 2).
variables, many scientific papers have attempted to
define the characteristics of these systems. We propose
in the following a classification of their characteristics
according to certain criteria, and based on the works of:
[Liu17], [Raw14], [Raj10], [Kim12] and [Haq14].
•Hybrid: CPS collects the information of physical
world (continuous variable) and transmits that
information to virtual worlds (discrete event), where
information is processed and sent back to the physical
world. Hybrid system refers to those systems that
explicitly and simultaneously involve continuous
variables and discrete events and have mutual influence
and interaction. Therefore the hybrid system is a
foundation of CPS.
•Heterogeneous: The components of a cyber-
physical system are of various types consisting of
computing devices, interfaces, distributed sensors and
actuators, and requiring interfacing and interoperability
across multiple platforms and different models of
computation.
•Dynamic: The environment of the CPS evolves
continually and thus the design and operations of the
system must account for such dynamic changes in the Figure 2. Structure of CPS.
environment.
Inspired by some models [Ala17] and [Pat11] that
have been proposed in the closely related fields of
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Domain Model for Cyber-Physical Systems ICAASE'2018
Internet of things, wireless sensors networks and as well. the Device would be modelled as an entity
software engineering in general, we have extracted the itself, with regard to specific application, whose
concepts and associations that we believe are suitable principle issue is the devices and not the physical
for representing applications in the field of CPS. These entity. For instance device management is used for
concepts are a refinement of the most relevant concepts managing or configuring the physical devices, ports
and interfaces of a computer or server.
found on comprehensive overviews of recently research
publications and CPS applications from the real world Human- might be a part of the physical part,
since the human could be considered as a physical
[Ala17], [Tan08] and [Raj14].
entity that the CPS is sensing and acting on. Health
In this section, we present our domain model for monitoring is a decent case of this.
CPS as shown in figure 3. The model is described using
a UML class diagram [OMG14]. This last illustrates Cyber-Physical part:
the entities of the CPS domain model involved, as well
as the interactions between domain concepts, including From CPS domain model point of view, Cyber-
cardinalities of such relationships. The remainder of Physical part includes components that provide an
this section is dedicated to the description of the four interface between the physical and cybernetic world. It
converts data and information collected from the
main aspects of the model and the interfaces between
physical world into digital data for use in the cybernetic
these aspects. world. It includes transducers that can be sensor or
actuator and user interfaces.
3.1 The main abstract concepts and Sensor- defines the set of possible sensing
relationships devices usable to sense the physical entity. Sensors
By applying separation of concerns design provide information, knowledge, or data about the
principal, we divide the CPS concepts into five physical properties of the physical entity and
major parts. generate a d igital representation of the
measurement corresponding to physical process.
Physical part: Thermometer and accelerometer are examples of
sensors.
As the CPS pertains to the physical Actuator- defines the set of possible actuating
world, the characteristics of the physical world devices usable to effect a change in the physical
play an important role. It concerns the concepts world by triggering actions (e.g. rotate, switch on
related to the real world. /off, translate…) based on output from processing
Physical process- is the observable in the cybernetic world. Heating or cooling
phenomenon that consists of a set of physical elements, speakers, lights are examples of actuators.
properties of the associated Physical Entity. User interface- defines a set of tasks designed
The temperature of a room is an example of a to help a user to interact with physical entities by
physical process. means of a given CPS application. For various
Physical Entity- is an identifiable element purposes such as:
of the physical environment that is of interest to o gaining information- The physical entities are
the user for the completion of her goal. For observed by sensors, and then the observed
instance it can be any object or environment information is sent; such as providing information
that the CPS senses and acts on, such as rooms, about electricity consumption or receiving a fire
cars, animals, humans, book, electronic appliances, notification in case of emergency to remote users.
jewellery or clothes, etc. o Controlling actuators- A user through user
interface can control an actuator by triggering a
The Physical Entity consists of the physical command (e.g., switch off the heater / controlling a
processes which represent properties that describe heater according to a temperature preference).
it. Furthermore, the entity of the physical world has
a context representing the location where is
situated. Locations of the entities are useful in
almost every application and as a result are included
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Domain Model for Cyber-Physical Systems ICAASE'2018
Figure 3. UML representation of the CPS Domain Model.
physical process that is used by others or fed
Cybernetic part: directly to a data stored service or a control decision
that triggers an action of an actuator.
The cybernetic part includes executable code for
Storage element- provides access to a
accessing, processing, and storing sensor information
datastores for storing and managing a collection of
and produce new information, as well a code for
data related to the monitored physical entities.
controlling actuators. It comprises computational
elements and storage elements. CPS application- is an end-user application. It
Computational element- takes input from is a type of cyber component, consists of
sensor or non-sensor data sources (for example, computational services that is designed to assist a
other processors and datastores), and processes it user to perform tasks by interacting with other cyber
according to a defined algorithm, and generates an components.
output. An output could be information message Cyber components communicate with each other
representing the measurement corresponding to in a well-known and consistent manner to exchange
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Domain Model for Cyber-Physical Systems ICAASE'2018
data and control to reach a common goal. data), and they may provide actuation
capabilities as well, and hardware elements
Data & Information part: which must have at any rate some level of
communication, computation and storage
Information services allow querying, changing and abilities for the purposes of the CPS.
adding information about the physical entity in
question. There are two types of information:
Sensory Data- Sensors collects the data of 4 Disccussions
physical world which cyber components Based on the definition of cyber-physical
consume as inputs. They are described by a set systems we extracted commonalities and created a
of attributes as well as equations and CPS Domain model applicable to cyber-physical
constraints between the attributes (called systems. We cite the following benefits of our
invariants) to define the laws of physics domain model:
describing the inputs, Generality: The CPS Domain Model is
Information- They are the physical independent of specific technologies. It defines the
outputs which are generated by the computational language, the concepts, and the entities of the CPS
elements in order to provide a meaningful world and how they are related to each other, which
representation of the Physical Entity. These do not change from one application to other and
outputs could be the Measurement which is thus, introduced the foundation of CPS which
characterized by a set of attributes to often serves as a base of knowledge about a specific
measure the physical process application in this broad domain.
corresponding to the physical entity or the Modularity: Development of CPS is a
control decision used by the actuator to trigger sophisticated activity which requires a
an action so as to affect the physical entity. multidisciplined approach where knowledge from
The information also can be used by other multiple concerns intersects, since varied set of
cyber components to perform other tasks or to skills are required during the process. By applying
be stored. separation of concerns design principle we have
divided the concepts and the associations among
Deployment part: them into different parts each part addresses a
separate concern, which is matched with a precise
The concepts that fall into this part describe stakeholder according to skills. The special value of
information about devices. this separation is to allow stakeholders to developed
Physical Device- is a technical component and updated independently.
which is a combination of hardware and software In order to support the development of CPS
forming a usable computing system that based on CPS domain model a development
performs some kind of computation and methodology can be proposed. It comprises three
exposes some intelligence. It provides the steps. At first, the System Requirements must be
ability of interacting with other devices and gathered, analyzed, and afterward used to instantiate
with the external environment. Mobile phones the CPS Domain Model, along these lines getting
and smart watch are examples of devices. A CPS Domain Model of the particular system that
physical device hosts a number of resources and has to be implemented. In the conceptual high-level
is connected to a network of other model a representation of the high-level features, at
computer controlled physical devices. It can be cyber, physical, cyber-physical, deployment and
aggregations of several Devices of different types. information concern, are acquired. . Each concern is
The devices can be attached to or embedded matched with a precise stakeholder according to
in the entities themselves – thus creating smart skills and abilities. The obtained model can be
things. A good example for that is healthcare iteratively refined in order to move from a
monitoring. Resource- It is any digital or conceptual high-level model to a more detailed one.
hardware components connected to a physical
device. It comprises cyber components that offer
information about the things (identifier, sensed, 5 Conclusion
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Domain Model for Cyber-Physical Systems ICAASE'2018
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domain model understandable to a large audience. [Bah11] R. Baheti., and H. Gill., "Cyber-physical
Indeed, we have highlighted some concepts and Systems". In:Samad, T., Annaswamy, A.M. (eds.), IEEE
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These abstractions are independent from any particular
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reduce some barriers in scientific discourse regarding [Gua16] X. Guan., Senior, Yang B., Chen C., Dai W.,
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Our future work intends to finalize the model by
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and including information about runtime platform Physical Systems: A Perspective at the Centennial",
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model for CPS. [Ala17] K. M. Alam., and A.El Saddik., "C2PS: A
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