SpaceFOM is the reference standard adopted by space agencies for simulating space missions. Although specifically designed for handling space systems, it currently faces a significant limitation when simulating interplanetary missions: a fixed Federation Time Step. This constraint hinders accurate and flexible modeling of space missions, which limits the dynamic changes of simulation pace, especially during critical phases that require particular temporal granularities. This work proposes extending the SpaceFOM standard to address this issue by enabling dynamic adjustment of Federation Time Step granularity. The proposed solution allows fine-grained time steps for mission-critical phases and coarse-grained steps for extended phases while smoothly combining continuous temporal progression. Furthermore, the proposed solution is general-purpose and can be applied to other domains requiring dynamic temporal granularity.

Abstract To capture the dynamics of modern Cyber-Physical Systems, hybrid system models are introduced to combine their continuous dynamics with the discrete ones. Unfortunately, one important negative issue can affect hybrid system models: the so-called Zeno phenomenon, which results in an infinite number of discrete transitions in a finite amount of time occurring during the model’s simulation that leads to inconsistent results. In this context, the paper investigates the use of a recently proposed numerical algorithm, based on the Infinity Computer methodology, to handle the Zeno phenomenon and evaluate it with respect to standard numerical methods by considering the hybrid system models of two exemplary Cyber-Physical Systems: the Water tanks and the Thermostat.

Today, the design and development of space systems are conducted cooperatively by historical space agencies in this area such as NASA, ESA, Roscosmos, and JAXA together with their industrial partners. The space system lifecycle is characterized by high costs, uncertain conditions, and dangerous scenarios. To mitigate these issues, space agencies rely heavily on Modelling and Simulation as a key technology to support the analysis, design, and operation of space systems. To support large-scale distributed simulations, the scientific community has developed several standards to support the reuse and interoperability of simulation models such as IEEE 1516 High-Level Architecture (HLA), Real-time Platform Reference Federation Object Model (RPR FOM), Simulation Model Portability (SMP), and the novel Space Reference Federation Object Model (SpaceFOM). While the SpaceFOM standard has been specifically conceptualized for handling space systems, the other ones are more general-purpose and can be used to design and simulate generic complex systems. As a consequence, there is a lake of rules and guidelines to enable interoperability among these standards. The paper presents solutions and experiences for enabling interoperability and transferability of HLA, RPR FOM, and SMP simulation models with SpaceFOM.

Abstract The increasing complexity of cyber-physical systems (CPSs) makes their design, development and operation extremely challenging. Due to the nature of CPS that involves many heterogeneous components, which are often designed and developed by organizations belonging to different engineering domains, it is difficult to manage, trace and verify their properties, requirements and constraints throughout their lifecycle by using classical techniques. In this context, the paper presents an integrated solution to formally define system requirements and automate their verification through simulation. The solution is based on the FOrmal Requirements Modeling Language and the Modelica language. The solution is exemplified through two case studies concerning a Trailing-Edge High-Lift system and a Heating, Ventilation and Air Conditioning system.

Counterfeiting represents one of the most widespread phenomena at a global level that indiscriminately affects all product sectors, from fashion to food, from medicines to digital media. The fight against counterfeiting remains a significant challenge for industries. Most of the current supply chains rely on centralized authorities or intermediaries that are not sufficient robust to guarantee anti-counterfeiting and traceability of goods.

Researchers and leading IT companies are increasingly proposing hybrid cloud/edge solutions, which allow to move part of the workload from the cloud to the edge nodes, by reducing the network traffic and energy consumption, but also getting low latency responses near to real time. This paper proposes a novel hybrid cloud/edge architecture for efficiently extracting Regions-of-Interest (RoI) in a large scale urban computing environment, where a huge amount of geotagged data are generated and collected through users's mobile devices. The proposal is organized in two parts: ($i$) a modeling part that defines the hybrid cloud/edge architecture capable of managing a large number of devices; (ii) a simulation part in which different design choices are evaluated to improve the performance of RoI mining algorithms in terms of processing time, network delay, task failure and computing resource utilization. Several experiments have been carried out to evaluate the performance of the proposed architecture starting from different configurations and orchestration policies. The achieved results showed that the proposed hybrid cloud/edge architecture, with the use of two novel orchestration policies (network- and utilization-based), permits to improve the exploitation of resources, also granting low network latency and task failure rate in comparison with other standard scenarios (only-edge or only-cloud).

The ever-growing advances in science and technology have led to a rapid increase in the complexity of most engineered systems. Cyber-physical Systems (CPSs) are the result of this technology advancement that involves new paradigms, architectures and functionalities derived from different engineering domains. Due to the nature of CPSs, which are composed of many heterogeneous components that constantly interact one another and with the environment, it is difficult to study, explain hypothesis and evaluate design alternatives without using Modeling and Simulation (M&S) approaches. M&S is increasingly used in the CPS domain with different objectives; however, its adoption is not easy and straightforward but can lead to pitfalls that need to be recognized and addressed. This paper identifies some important pitfalls deriving from the application of M&S approaches to the CPS study and presents remedies, which are already available in the literature, to prevent and face them.

Abstract Numerical computing is a key part of the traditional computer architecture. Almost all traditional computers implement the IEEE 754-1985 binary floating point standard to represent and work with numbers. The architectural limitations of traditional computers make impossible to work with infinite and infinitesimal quantities numerically. This paper is dedicated to the Infinity Computer, a new kind of a supercomputer that allows one to perform numerical computations with finite, infinite, and infinitesimal numbers. The already available software simulator of the Infinity Computer is used in different research domains for solving important real-world problems, where precision represents a key aspect. However, the software simulator is not suitable for solving problems in control theory and dynamics, where visual programming tools like Simulink are used frequently. In this context, the paper presents an innovative solution that allows one to use the Infinity Computer arithmetic within the Simulink environment. It is shown that the proposed solution is user-friendly, general purpose, and domain independent.

Modern systems are exposing an ever increasing degree of complexity also due to the heterogeneity of the involved components. Distributed simulation is widely recognized as an effective tool to carry out verification and validation activities for heterogeneous and complex systems. Unfortunately, the use of distributed simulation frameworks and related implementation technologies require a proper modeling and simulation know-how, as well as a significant effort and software development skills. As a result, distributed simulation is not typically addressed by systems engineers who do not have the required expertise or background. The MONADS model-driven method has been introduced to overcome such limitations and provide systems engineers with the ability to properly carry out simulation-based verification and validation activities. The method specifically addresses the HLA (High Level Architecture) distributed simulation framework and introduces an automated approach to generate a significant portion of the HLA code from system models specified in SysML, the standard modeling language in the systems engineering field. The automatically obtained code is then to be finalized by a manual programming activity. This paper contributes to make easier and further reduce the effort of such a manual activity by integrating the reactive features of the RxHLA framework into the MONADS method. This integration enables the use of streams to effectively manage HLA-based asynchronous interactions. The paper describes the technical details of the various strategies that can be used to integrate RxHLA into the MONADS method, thus providing a significant degree of flexibility to MONADS users.

Distributed and Real-Time Simulation represents a solid and effective approach to manage the ever-increasing complexity of modern systems. The IEEE 1516-2010 for Modeling and Simulation (M&S) High Level Architecture (HLA) is an interoperability standard for Distributed Simulation (DS) used to support analysis, engineering and training in different research and industrial domains. Using HLA, simulation entities (called Federates) can interact (that is, to publish and/or subscribe ObjectClasses and InteractionClasses, to communicate data, and to synchronize actions) with other Federates in a common simulation environment (called Federation) through the services provided by the Run-Time Infrastructure (RTI) that abstract and hide the details of the computing infrastructures making them communicable. In today's HLA-DS systems, in which simulation entities are highly concurrent, distributed, and the interactions among them are asynchronous, great benefits can derive from the exploitation of reactive approaches, tools and techniques so as to reactively manage the Federates' communication flow instead of handling it through HLA Callbacks. In this context, the paper presents a solution for defining reactive HLA Federates along with the RxHLA software framework that aims at defining and building reactive, concurrent, and distributed time/event-driven simulation components (Federates) in a r.eactive fashion.

The design and development of modern Large-Scale systems and System-of-Systems (SoSs) requires the use of new Modeling and Simulation (M&S) methods, models and techniques so as to manage their ever-increasing complexity. In this context, distributed simulation (DS) can effectively support the analysis and design of these systems by enabling the evaluation and comparison of different design choices. In the DS domain the IEEE 1516-2010 - High Level Architecture (HLA) represents the most mature standard. Unfortunately, the development of DS compliant with the HLA standard is a challenging and costly task. To overcome this problem, the Business Process Model and Notation (BPMN) standard could represent a viable solution, since it offers a standardized graphical notation based on a flowcharting technique that allows developers to easily specify the behavioral view of such a system in terms of business processes. The paper presents a Model-Driven method that, according to the Model-Driven systems engineering paradigm, allows to generate the HLA-based simulation code from BPMN models by use of a chain of model-to-text transformations.

Summary Cybersecurity compliance analysis is the process of assessing whether the behavior of an IT system or application conforms to the cybersecurity rules and regulations in force. This assessment can be offered as a service by exploiting available cloud technologies, and, indeed, it is one of the services classified by the Cloud Security Alliance (CSA) as part of the security information and event management (SIEM) category of the SecaaS (security as a service) domain. The definition and implementation of this typology of cloud services are challenging activities due to the complexity of both the reference business domain and the compliance analysis services to be provided themselves. The paper exploits a recently proposed requirements methodology, called GOReM (goal‐oriented requirements methodology), to support the conceptualization and subsequent implementation of cybersecurity compliance analysis services. In particular, two different application scenarios regarding compliance analysis of an existing or under development IT system/application are presented and discussed. In both the scenarios, GOReM allows to grasp and understand the many and complex issues to address for providing secure cloud services to worldwide customers, also due to the numerous, different and ever changing legal aspects, which have to be taken into account by service providers.

In the Risk Analysis domain an increasing interest has been gaining by the System Risk Analysis that aims at investigating the risk deriving by the interdependence of the system under consideration by other systems and, in general, by the interactions among them. Indeed, an adverse event occurring in a certain system can cause negative effects on the other interconnected systems and compromise their operation. An effective analysis of the Systemic Risk requires suitable methods and techniques able to handle the high level of complexity typical of Systems and Systems characterized by several interconnected, distributed, autonomous and changing components. In this context, the paper proposes a method for Systemic Risk Analysis that combines a Goal-Oriented Methodology for Requirement Modeling (GOReM) with a Model-Based method for System Dependability Analysis (RAMSoS). Such combination enables the modeling and the evaluation of Systemic Risk scenarios by using agent-based simulations and the complementary quantitative evaluation of performance indices through Bayesian Networks. A concrete exploitation of the proposed approach to Systemic Risk Analysis in the cyber-security domain is also presented1.

The IEEE 1516-2010 - Standard for Modeling and Simulation High Level Architecture (HLA) range of standards are widely used for distributed simulation, interoperability, reusability and the modeling of large-scale systems in many application domains. Although it provides several advantages, the development of distributed simulations based on the HLA standards remains a challenging task that requires a considerable effort in terms of time, cost and expertise. The HLA Development Kit software framework (DKF) is a software framework that aims to facilitate the development of HLA-based distributed simulations. This tutorial presents an overview of the DKF and a methodology for its use. Examples of the DKF in action are given from the Simulation Exploration Experience (SEE), a worldwide project led by NASA that annually gives the opportunity to build collaboratively a distributed simulation of a scientific base placed on the moon surface.

In the Space domain the High Level Architecture (HLA) is one of the reference standard for Distributed Simulation. However, for the different organization involved in the Space domain (e.g. NASA, ESA, Roscosmos, and JAXA) and their industrial partners, it is difficult to implement HLA simulators (called Federates) able to interact and interoperate in the context of a distributed HLA simulation (called Federation). The lack of a common FOM (Federation Object Model) for the Space domain is one of the main reasons that precludes a-priori interoperability between heterogeneous federates. To fill this lack a Product Development Group (PDG) has been recently activated in the Simulation Interoperability Standards Organization (SISO) with the aim to provide a Space Reference FOM (SRFOM) for international collaboration on Space systems simulations. Members of the PDG come from several countries and contribute experiences from projects within NASA, ESA and other organizations. Participants represent government, academia and industry. The paper presents an overview of the ongoing Space Reference FOM standardization initiative by focusing on the solution provided for managing the execution of an SRFOM-based Federation.

An architecture-based model-driven design approach, enabled by tools for system synthesis, simulation, and simulation content management, is exploited to efficiently explore design variants at a system level. This paper shows a case study where this design is successfully applied to an aircraft leading-edge slat system. In this case, different variants of design were investigated and compared.

Distributed and Real-Time Simulation plays a key-role in the Space domain being exploited for missions and systems analysis and engineering as well as for crew training and operational support. One of the most popular standards is the 1516-2010 IEEE Standard for Modeling and Simulation (M&S) High Level Architecture (HLA). HLA supports the implementation of distributed simulations (called Federations) in which a set of simulation entities (called Federates) can interact using a Run-Time Infrastructure (RTI). In a given Federation, a Federate can publish and/or subscribes objects and interactions on the RTI only in accordance with their structures as defined in a FOM (Federation Object Model). Currently, the Space domain is characterized by a set of incompatible FOMs that, although meet the specific needs of different organizations and projects, increases the long-term cost for interoperability. In this context, the availability of a reference FOM for the Space domain will enable the development of interoperable HLA-based simulators for related joint projects and collaborations among worldwide organizations involved in the Space domain (e.g. NASA, ESA, Roscosmos, and JAXA). The paper presents a first set of results achieved by a SISO standardization effort that aims at providing a Space Reference FOM for international collaboration on Space systems simulations.

The development of high quality complex software systems and quick time-to-market with full customer satisfaction often appear as two competing forces. Many industry efforts have been directed towards agile methodologies completed with the DevOps approach, whereas traditional requirements engineering with much documentation, is considered surpassed. The aim is to obtain a longer life software because it suddenly responds to the customers changing requirements from which it receives continuous input. This might create a serious cost implication and a real risk to lose system requirements control. In this paper, we propose a framework able to govern the complexity of the system requirements and to allow the embedding, occasionally, of technological innovations into the overall system. ResDevOps joins the value of the agile world with DevOps, with the additional value deriving from an unceasing parallel innovation management process, which we call ResDevs. ResDevOps includes a continuous research and innovation process, which provides an asynchronous, additional input to the agile process inside a chain of concurrent engineering collaboration. This is a suitable trade-off to maintain modern IT Systems live for a longer time, with many consequent advantages for both total investment and system quality. The practical use of the ResDevOps approach is shown by means of a case study.

The Modeling & Simulation (M&S) of modern cyber-physical systems is presenting new challenges. New M&S techniques, methods and tools are emerging that take advantage of distributed simulation environments. One of the most mature and popular standard for distributed simulation is the IEEE 1516-2010 - High Level Architecture (HLA) that, although originally developed for military applications, is increasingly exploited in a great variety of application domains due to its capabilities to enable the interoperability and reusability of distributed simulation components. However, the development of fully fledged simulation models, based on the IEEE 1516-2010 standard, is still a challenging task and requires considerable development effort that often results not only in an increase in development time but also in low reliability. In this context, the paper presents a general-purpose, domain-independent framework that aims to ease the development of HLA-based simulations. Its effectiveness is exemplified in the context of the Simulation Exploration Experience (SEE) project lead by NASA and which involves several U.S. And European Institutions.

The IEEE 1516-2010 High Level Architecture for distributed simulation is used to facilitate the development of large-scale simulations. However, there is a steep learning curve. The annual Simulation Exploration Experience (SEE) presents the opportunity for multiple international student-led teams to gain experience in developing distributed simulations in an interesting lunar-based scenario. To support the student learning process, a prototype HLA Development Kit has been created that has the goal of reducing the complexity of distributed simulation design and implementation. A student-led team used the Kit to create a lunar excavator federate using agent-based simulation implemented in REPAST. The excavator federate successfully interoperated with the University of Liverpool UAV during SEE 2015. This paper presents a short overview of the Kit and experiences in developing the lunar excavator federate.

Compliance analysis is an important step for the security management process of systems. It aims at both increasing service quality and reducing service vulnerabilities by exploiting security mechanisms able to improve the fulfillment of requirements whose failure may cause direct and indirect costs, related to the existence of missed normative provisions, risk of loss of certifications, and increased probability and impact of security incidents. Due to the increasing in system complexity there are hundreds of requirements that must be observed simultaneously and satisfied. As a consequence, the need for innovative approaches centered on effective solutions able to support the evaluation and the validation of requirements and constraints over the time is today greater than ever. In this context, the paper proposes a method for supporting the compliance assessment of services, in respect of norms and regulations, exploitable both in design phase or during the operation of existing services supported by (semi-)automatic tools. The effectiveness of the method is then tested through a case study taken from the experience of the Computer Emergency Response Team (CERT) of Poste Italiane, concerning the compliance assessment of an Electronic Payment Service by credit card.

The paper presents UNICOM, a project based on HLA (High Level Architecture) that aims at providing: (i) flexible communication services to the entities populating a Moon base simulated scenario and (ii) a real-time 3D visualization of this scenario by connecting the MÄK RTI (Run Time Infrastructure) and Unity 3D. UNICOM has been developed in the context of the 2014 edition of the Simulation Exploration Experience (SEE), an event organized by the Simulation Interoperability Standards Organization (SISO), in collaboration with NASA and other research and industrial partners, with the objective to promote the adoption of the HLA standard and compliant tools by involving university teams in the distributed simulation of a Moon base. The paper aims also to share the experience of the University of Calabria Team in participating to the SEE initiative so to encourage and guide the participation of new teams to the next editions of this exciting event.