System-of-systems Research Articles

The MED-SUV virtual research environment for enabling the GEO Geohazard supersites in Italy

This paper presents the Virtual Research Environment (VRE) enabling two European GEO Geohazard Supersites in Italy. According to GEO (Group on Earth Observation) vision, Geohazard Supersites provide access to spaceborne and in-situ geophysical data and models for selected sites prone to natural hazards –noticeably, earthquakes and volcano eruptions. The VRE was implemented in the framework of the Mediterranean Supersite Volcanoes (MED-SUV) project, funded by the European Commission. MED-SUV realized one of the European supersite demonstrators covering the two Permanent Supersites selected in Italy: Mt. Etna and Campi Flegrei/Vesuvius. The MED-SUV VRE provides advanced services for heterogeneous data and information management and sharing. MED-SUV started identifying the main supersite requirements including: the interoperability with existing data/information supply systems, the support of policy-based access control, the access to processing capabilities provided by external platforms, the management resources for publishing and sharing new products, the integration with significant global systems such as GEOSS and EPOS. MED-SUV adopted a System of Systems (SoS) approach to address interoperability with the identified heterogeneous systems supplying data and information. The SoS approach is based on a brokering architecture, where a specialized component (i.e the MED-SUV Broker: MSB) connects the existing and next-coming data sources leaving them autonomous. MSB carries out all the necessary mediation and harmonization tasks exposing standard interfaces enabling the interconnection with external systems like GEOSS and EPOS. In addition, MSB is accessible via a JavaScript library implementing Web APIs to facilitate the development of Web and mobile applications.

Exploring Systemic Risks in Systems-of-Systems Within a Multiobjective Decision Framework

Physical infrastructures are commonly composed of interconnected and intra- and interdependent subsystems, which in their essence constitute systems-of-systems (S-o-S) with multiple functions, operations, and stakeholders. Their complexity is characterized by highly interconnected and interdependent physical, cyber, organizational, and economic subsystems through shared resources, decisions, and states. This paper explores potential sources of systemic risks in complex S-o-S by analyzing unique failure modes of such systems in a nonlinear dynamic multiobjective sequential decision-making process. We posit that certain preferences of decision-makers when choosing among multiple competing objectives may reduce the safety margin of a specific subsystem within the S-o-S to withstand unexpected external perturbations due to the interdependencies manifested by shared states among the subsystems. This can contribute to the failure of an entire S-o-S even though all decisions are made based on Pareto-optimality. By quantifying the level of subsystem interdependency caused by shared states, this paper develops a method to mitigate such systemic risks through decomposing and coordinating the interconnected subsystems of an S-o-S in a decentralized way. The implication of the proposed theory is demonstrated using an illustrative example of a highway bridge S-o-S.

A System of Systems approach for data centers optimization and integration into smart energy grids

This paper addresses the problem of proactive planning and optimizing the operation of a Systems of Systems (SoS) over a time horizon while considering the characteristics of each constituent system and complex interactions among them. We define a mathematical formalism for modeling complex systems composed of a mesh of sub-systems with linear and non-linear behaviors and abstractions like discrete time, atomic systems and interconnection of atomic system. The proposed modeling approach is simple enough to allow fast computations and simulations, and at the same time complex enough to capture the essential features of the real system thus allowing the mapping of proactive optimization problems to Mixed-Integer Optimal Control Problems. The proactive planning uses hierarchical optimization processes that compute predictions and optimization plans at various time granularities, each finer layer plan adjusting and refining the ones with higher granularity. To show case our approach we model a Data Center which is a well-known case of a large scale complex system aiming to plan and optimize its operation to use as much as possible the locally produced renewable energy and optimize its integration in smart grid advanced context. Simulation based results show a reduction of 5% of the carbon footprint and at the same time an increase in profit of more than 14% due to flexible energy shifting.

Cloud Computing Cost and Energy Optimization through Federated Cloud SoS

The two most significant differentiators among contemporary cloud computing service providers have increased green energy use and data center resource utilization. This paper addresses these two issues from a system's architectural optimization viewpoint. The proposed approach herein allows multiple cloud providers to utilize their individual computing resources in three ways by: (1) cutting the number of datacenters needed, (2) scheduling available datacenter grid energy via aggregators to reduce costs and power outages, and lastly by (3) utilizing, where appropriate, more renewable, and carbon-free energy sources. Altogether our proposed approach creates an alternative paradigm for a federated cloud system-of-systems (SoS) approach. The proposed paradigm employs a novel control methodology that is tuned to obtain both financial and environmental advantages. It also supports dynamic expansion and contraction of computing capabilities for handling sudden variations in service demand as well as for maximizing usage of time-varying green energy supplies. Herein we analyze the core SoS requirements, concept synthesis, and functional architecture with an eye on avoiding inadvertent cascading conditions. We suggest a physical architecture that diminishes unwanted outcomes while encouraging desirable results. Finally, in our approach, the constituent cloud services retain their independent ownership, objectives, funding, and sustainability means.

Risk Modeling of Interdependent Complex Systems of Systems: Theory and Practice.

The emergence of the complexity characterizing our systems of systems (SoS) requires a reevaluation of the way we model, assess, manage, communicate, and analyze the risk thereto. Current models for risk analysis of emergent complex SoS are insufficient because too often they rely on the same risk functions and models used for single systems. These models commonly fail to incorporate the complexity derived from the networks of interdependencies and interconnectedness (I-I) characterizing SoS. There is a need to reevaluate currently practiced risk analysis to respond to this reality by examining, and thus comprehending, what makes emergent SoS complex. The key to evaluating the risk to SoS lies in understanding the genesis of characterizing I-I of systems manifested through shared states and other essential entities within and among the systems that constitute SoS. The term "essential entities" includes shared decisions, resources, functions, policies, decisionmakers, stakeholders, organizational setups, and others. This undertaking can be accomplished by building on state-space theory, which is fundamental to systems engineering and process control. This article presents a theoretical and analytical framework for modeling the risk to SoS with two case studies performed with the MITRE Corporation and demonstrates the pivotal contributions made by shared states and other essential entities to modeling and analysis of the risk to complex SoS. A third case study highlights the multifarious representations of SoS, which require harmonizing the risk analysis process currently applied to single systems when applied to complex SoS.

Systems‐of‐systems modeling using a comprehensive viewpoint‐based SysML profile

AbstractIn recent years, more and more efforts have been devoted in supporting the design of systems‐of‐systems (SoS). Designing such systems is a multidisciplinary problem which involves considering emergent phenomena, assuring the achievement of dependability/security requirements, guaranteeing system responsiveness, and supporting dynamicity/evolution and multicriticality of provided services. A first step towards a viable design approach is to provide a conceptual model of SoS which captures SoS concepts, and their interrelationships aiming at enhancing the understandability of SoS to stakeholders and providing the basis for further automated analysis. In this context, the AMADEOS European project is bringing together researchers and practitioners to provide the support to design SoS starting from the definition of a domain specific ontology serving as a vocabulary for SoS. Our contribution consists in the modeling of the key SoS concepts and relationships defined in AMADEOS adopting a systems modeling language visual modeling language. We propose a systems modeling language profile for SoS, and we show its applicability in a Smart Grid scenario. We show how to use the profile in a model‐driven engineering process to support different types of analyses, and we discuss how to integrate the profile in a user‐friendly model‐driven engineering tool for SoS rapid modeling, validation, code‐generation, and simulation.

Agile digital transformation of System-of-Systems architecture models using Zachman framework

Abstract Emergent behavior is behavior of a system that does not depend on its individual parts, but on their relationships to one another. Such behavior exists in biological systems, physical systems as well as in the human performance. It is an inherited nature of a System-of-Systems (SoS). A suitable framework is needed to guide the development of SoS architecture, which includes emergent behavior. Enterprise architecture (EA) is a discipline driving change within organizations. Aligning and integrating business and IT thereby belongs to strategic management. The management of EA change is a challenging task for enterprise architects, due to complex dependencies amongst EA models, when evolving towards different alternatives. In this paper, various architecture frameworks are explored for an application on SoS architecture: the Department of Defense Architecture Framework (DoDAF) and Ministry of Defense Architecture Framework (MODAF) are declared inappropriate. The Open Group Architecture Framework (TOGAF), the Federal Enterprise Architecture Framework (FEAF) and the Zachman Framework on the other hand are suitable. The use of Zachman Framework to guide the architecture development is described in step-by-step details in this paper. The agent-based simulation is recommended to develop the SoS architectural models following the Zachman Framework guidance. Ultimately, SysML and UML should be integrated with the agent-based model. An example with the collaborative engineering services for the global automotive supply chain is hereby described.

Modelling System of Systems Interface Contract Behaviour

A key challenge in System of Systems (SoS) engineering is the analysis and maintenance of global properties under SoS evolution, and the integration of new constituent elements. There is a need to model the constituent systems composing a SoS in order to allow the analysis of emergent behaviours at the SoS boundary. The Contract pattern allows the engineer to specify constrained behaviours to which constituent systems are required to conform in order to be a part of the SoS. However, the Contract pattern faces some limitations in terms of its accessibility and suitability for verifying contract compatibility. To address these deficiencies, we propose the enrichment of the Contract pattern, which hitherto has been defined using SysML and the COMPASS Modelling Language (CML), by utilising SysML and Object Constraint Language (OCL). In addition, we examine the potential of interface automata, a notation for improving loose coupling between interfaces of constituent systems defined according to the contract, as a means of enabling the verification of contract compatibility. The approach is demonstrated using a case study in audio/video content streaming.

Applying a model-based methodology to develop web-based systems of systems

Systems of Systems (SoS) are emerging applications composed by subsystems that interacts in a distributed and heterogeneous environment. Web-based technologies are a current trend to achieve SoS user interaction. Model Driven Web Engineering (MDWE) is the application of Model Driven Engineering (MDE) into the Web development domain. This paper presents a MDWE methodology to include Web-based interaction into SoS development. It's composed of ten models and seven model transformations and it's fully implemented in a support tool for its usage in practice. Quality aspects covered through the traceability from the requirements to the nal code are exposed. The feasibility of the approach is validated by its application into a real-world project. A preliminary analysis of potential bene ts (reduction of e ort, time, cost; improve of quality; design vs code ratio, etc) is done by comparison to other project as an initial hypothesis for a future planned experimentation research.

A quality requirements model and verification approach for system of systems based on description logic

System of systems engineering (SoSE) involves the complex procedure of translating capability needs into the high-level requirements for system of systems (SoS) and evaluating how the SoS quality requirements meet their capability needs. One of the key issues is to model the SoS requirements and automate the verification procedure. To solve the problem of modeling and verification, meta-models are proposed to refine both functional and non-functional characteristics of the SoS requirements. A domain-specific modeling language is defined by extending Unified Modeling Language (UML) class and association with fuzzy constructs to model the vague and uncertain concepts of the SoS quality requirements. The efficiency evaluation function of the cloud model is introduced to evaluate the efficiency of the SoS quality requirements. Then a concise algorithm transforms the fuzzy UML models into the description logic (DL) ontology so that the verification can be automated with a DL reasoner. This method implements modeling and verification of high-level SoS quality requirements. A crisp case is used to facilitate and demonstrate the correctness and feasibility of this method.

Construction of composite indicator system based on simulation data mining

The indicator system is the foundation and emphasis in the effectiveness evaluation of system of systems (SoS). In the past, indicator systems were founded based on qualitative methods, and every indicator was mainly determined by the expert with experience. This paper proposed a brand-new method to construct indicator systems based on the repeated simulation of the scenario space, and calculated by quantitative data. Firstly, the selection of key indicators using the Gini indicator importance measure (IIM) is calculated by random forests (RFs). Then, principal component analysis (PCA) is applied when we use the selected indicators to construct the composite indicator system of SoS. Furthermore, a set of rulesare is developed to verify the practicability of the indicator system such as correlation, robustness, accuracy and convergence. Experiment shows that the algorithm achieves good results for the construction of composite indicators of SoS.

An Application of SMC to continuous validation of heterogeneous systems

This paper considers the rigorous design of Systems of Systems (SoS), i.e. systems composed of a set of heterogeneous components whose number evolves with time. Such components cooperate to accomplish functions that they could not achieve in isolation. Examples of SoS include smart cities or airport management system. The dynamical evolution of SoS behavior and architecture makes it impossible to design an appropriate solution beforehand. Consequently, existing approaches build on an iterative process that takes SoS evolution into account. A key challenge in this process is the ability to reason about and analyze a given view of the SoS (on a fixed number of SoS constituents) with respect to a set of goals, and use the results to eventually predict the evolution of the SoS. To address this challenge, we rely on a scalable formal verification technique known as Statistical Model Checking (SMC). SMC quantifies how close the current view is from achieving a given mission. We integrate SMC with existing industrial practice, by addressing both methodological and technological issues. Our contribution is: (1) a methodology for validation of SoS formal requirements; (2) a formal specification language able to express complex SoS requirements; (3) the adoption of current industry standards for simulation and heterogeneous systems integration ; (4) a robust SMC tool-chain integrated with system design tools used in practice.We illustrate the application of our SMC tool-chain and the obtained results on a case study.

Coordination of Constituent Systems for Functionalizing Systems of Systems: An Exploration

Coordinating the constituent systems of a system of systems (SoS) in operations is an important task for functionalizing the SoS. The choice of a coordinating strategy needs to consider the autonomy, belonging, and connectivity levels of constituent systems. The diversity and emergence characteristics of SoS are outcomes of coordination. This paper analyzes different strategies for coordinating constituent systems from the perspective of SoS characteristics and, therefore, derives the mechanism for choosing a coordinating strategy. Challenges are found in implementing the coordinating strategies for SoS. The paper summarizes representative challenges facing system engineers. Methods for addressing these are proposed, including the multi-stage multi-scale coordination and smart coordination of operating mode switches. An island energy system composed of both diesel engine generators and microgrids with renewable energy sources is presented in this paper as an example of SoS network. Various aspects of coordinating constituent systems in this SoS network are presented to illustrate how the choice and execution of coordinating strategies functionalize SoS.

SoS thinking: an approach to conceptualising and understanding military systems-of-systems

Systems-of-systems (SoS) are acknowledged as an engineering challenge for defence organisations, due to high complexity of various military SoS and their development processes. Challenges in achieving a clear and shared understanding of SoS problems and difficulties in managing complexity have undermined not only application effectiveness of architectural approaches and SoS methodologies, but also quality of their outcomes. This paper introduces SoS thinking that offers a language and process to effectively conceptualise, understand, communicate about and assess military SoS. Based on the proposed critical thinking in multi-dimensions, high complexity of SoS problems can be explored, contextualised and addressed through using a set of SoS lenses in a number of important aspects, including the engineering factor, diversity, relationships, design paradigm, development states and technical statuses.

A system of systems framework for autonomy with big data analytic and machine learning

Large data has been accumulating in all aspects of our lives for quite some time. Advances in sensor technology, the Internet, wireless communication, and inexpensive memory have all contributed to an explosion of “Big Data”. System of Systems (SoS) are integration of independent operatable and non-homogeneous legacy systems to achieve a higher goal than the sum of the parts. Today’s SoS are also contributing to the existence of unmanageable “Big Data”. Recent efforts have developed promising approach, called “Data Analytics”, which uses machine learning tools from statistical and soft computing (SC) such as principal component analysis (PCA), clustering, fuzzy logic, neuro-computing, evolutionary computation, Bayesian networks, deep architectures and deep learning, etc. to reduce the size of “Big Data” to a manageable size and apply these tools to a) extract information, b) build a knowledge base using the derived data, and c) eventually develop a non-parametric model for the “Big Data”. This keynote attempts to construct a bridge between SoS and Data Analytics to develop reliable models for such systems. A photovoltaic energy forecasting problem of a micro grid SoS, traffic jams forecasting and a system of autonomous vehicles will be offered for case studies. These tools will be used to extract a nonlinear Model for a SoS-generated BIG DATA. Videos for autonomous vehicles will be shown.

Maintaining System of Systems That Are Fit for Purpose: Effectively and Efficiently Preparing for the Unforeseeable

This article hypothesizes that a system of systems (SoS) that is not fit for purpose (FFP) is unfit because it cannot implement the correct, timely, and complete transfers of matter, energy, and information (MEI) between its constituents and with its external environment that are necessary to achieve a particular result. This research addresses the problem of maintaining an SoS FFP after unpredictable changes in operation, composition, or external factors by creating a method implemented as an engineering process and supported by an analysis technique to enhance the affordance of the SoS constituents for MEI transfer (MEIX) and to reveal potential undesirable transfers.

A Framework of System of Systems Design with Scenario, Multi-Agent Simulation and Robustness Assessment

A system of systems (SoS) is a heterogeneous, autonomous and complex systems. This paper aims at proposing a new framework of SoS design. First, this research discusses the complex situations of SoS, and addresses the three issues of SoS design: 1) nonlinearity and discontinuity of design space, 2) emergence behavior, and 3) high uncertainty. The framework adopts a scenario design method, a multi-agent simulation method, and a robust design method to solve these issues, and integrates them in a sophisticated manner. A case study of designing subsidy polices for a distributed generation system, which is a typical SoS, is demonstrated.

SoS thinking: an approach to conceptualising and understanding military systems-of-systems

SoS thinking: an approach to conceptualising and understanding military systems-of-systems

Decision Support Systems and Integrated Platforms: New Approaches for Managing Systems of Systems

Currently, in different contexts of strategic relevance, there is the increasing need of integrating and coordinating previously autonomous elements and systems to reach a common that is otherwise not achievable. Such a challenge requires competencies from many heterogeneous domains, leading to very complex and often ineffective management processes. The need to formalize a structured and unifying framework to support decision makers leads to the introduction of the systems of systems (SoS), that is, large-scale integrated systems that are heterogeneous and independently operable on their own, but are networked together for a common goal [1].

A system of systems view on integrating control for energy efficient building assessment

The ability to simulate combined control and building performance applications in a distributed manner is increasingly becoming an invaluable tool in the assessment of automated buildings (ABs) for better design and operation. To make such assessments without the need for costly and time consuming experiments, distributed simulations can be used so as to simultaneously fulfil the occupants' needs while minimising energy use and potentially reducing greenhouse gas emissions. Therefore, distributed simulations are necessary to assess the impact of control systems on building performance applications (i.e., building indoor environments) over a network. This paper describes the development and implementation of a unified framework based on a system of systems (SoS) concept for distributed control and building performance simulations involving two or more different software tools via a network. The main objective of this framework is to couple one or multiple building performance simulation tool(s) with a control systems modelling environment by run-time over a network in order to similarly represent building automation and control systems (BACS) architecture in a simulation. Finally, the paper ends with some conclusions and perspectives for future work.