System-of-systems Research Articles

Performance measurement and management in complex environments: a system of systems approach for the public sector

Issues related to rapidly changing digital environments and turbulent or complex settings, such as the public sector, often hinder successful implementations of Performance Measurement and Management (PMM) systems. Despite the availability of PMM methods, the challenge of implementing successful systems in turbulent settings persists. This article introduces a novel PMM framework employing a System of Systems (SoS) approach, integrating Data Envelopment Analysis and Machine Learning to guide organisational changes by enhancing the efficiency of Decision-Making Units (DMU). Validated by a case study within the Brazilian Navy, the framework demonstrates a significant capacity to interpret the impact of DMU characteristics on operational efficiency and draw actionable insights. Our findings suggest that leveraging SoS principles emphasises adaptability and ongoing improvement through a data-driven process, suggesting the framework’s potential to navigate through complexity by enabling more effective management practices and decision-making. Future research directions include longitudinal studies and the incorporation of technologies to support managerial decision-making.

Enhancing Energy Systems and Rural Communities through a System of Systems Approach: A Comprehensive Review

Today’s increasingly complex energy systems require innovative approaches to integrate and optimize different energy sources and technologies. In this paper, we explore the system of systems (SoS) approach, which provides a comprehensive framework for improving energy systems’ interoperability, efficiency, and resilience. By examining recent advances in various sectors, including photovoltaic systems, electric vehicles, energy storage, renewable energy, smart cities, and rural communities, this study highlights the essential role of SoSs in addressing the challenges of the energy transition. The principal areas of interest include the integration of advanced control algorithms and machine learning techniques and the development of robust communication networks to manage interactions between interconnected subsystems. This study also identifies significant challenges associated with large-scale SoS implementation, such as real-time data processing, decision-making complexity, and the need for harmonized regulatory frameworks. This study outlines future directions for improving the intelligence and autonomy of energy subsystems, which are essential for achieving a sustainable, resilient, and adaptive energy infrastructure.

Embracing multi-functionality in European infrastructure projects: A system of systems perspective

Infrastructure projects undergo multiple changes throughout their lifecycle, adapting to new mobilities, technologies and environments. We build on the System of Systems (SoS) theoretical concept to understand the implications of such infrastructure transformations, specifically when projects move from a single purpose to hosting multiple functions. Using multiple case studies in Europe, we investigate which functions will likely be added to the original infrastructure and the rationale for adding these functions. Therefore, we expand upon the theoretical concepts of circularity, resilience, and social sustainability, wherein multifunctional infrastructure adapts, renews, and complements existing infrastructure.

Model for Global Quality Management System in System of Systems

This study inaugurates an innovative field of research for Global Quality Management System (G-QMS) in System of Systems (SoS), integrating emerging and rapidly evolving disciplines of QMS, SoS Globalization, and Systems approaches, chiefly Systems Thinking. This manuscript introduces, for the first time, a conceptual model for G-QMS in sectors of SoS, developed from an extensive field study conducted in real SoS global organizations, employing the Grounded Theory methodology. We found that this model can be described by two separate supra entities, despite their extensive interrelationships. This manuscript focuses on the first supra entity, which constitutes the foundation for understanding the second supra entity. The model pertaining to the first supra entity, named G-QMS of G-Organization in Sectors of SoS, is introduced through a detailed description of its structural principles. Additionally, a detailed description of its complementary aspects and elements is provided, which condenses these principles into a complete conceptual model picture. This field of research is highly significant for such organizations. These organizations typically maintain leading and advanced quality bodies, especially in comparison to the broader industry. Therefore, the G-QMS model developed through this research can offer substantial contributions to these organizations, but also to all other global organizations.

System-of-Systems Resilience Analysis and Design Using Bayesian and Dynamic Bayesian Networks

A System-of-Systems (SoS) is characterized both by independence and by inter-dependency. This inter-dependency, while allowing an SoS to achieve its objectives, also means that failures can cascade throughout the SoS. An SoS needs to be resilient to deal with the impact of complex internal and external environments. In this paper, we propose a resilience analysis method of an SoS based on a hierarchy structure. Firstly, we establish a hierarchy structure, which is ranked from high to low as capability level, activity level and system level. Then, Bayesian Networks (BNs) and Dynamic Bayesian Networks (DBNs) are used to analyze the resilience of the SoS. A resilience-based system importance metric is introduced, which is used in the budget allocation optimization problem during the development domain of an SoS. This paper proposes a mathematical programming model aimed at optimizing SoS resilience by optimally using budget to the subsystem. The application of the proposed approach is demonstrated using a case study: a Next Generation Air Transportation setting. The study results provide evidence that the proposed inter-dependency analysis based on Bayesian theory and the SoS resilience design approach can assist SoS system engineers in increasing expected SoS resilience during the development domain.

Aviation armament system-of-systems modeling and identification method of vulnerable nodes based on interdependent network

Aiming at the problem that it is difficult to build model and identify the vulnerable equipment for aviation armament System-of-Systems (SoS) due to complex equipment interaction relationships and high confrontation, the interdependent network theory is introduced to solve it. Firstly, a two-layer heterogeneous interdependent network model for aviation armament SoS is proposed, which reflects the information interaction, functional dependency and inter-network dependence effectively. Secondly, using the attack cost to describe the confrontation process and taking the comprehensive impact on kill chains as the entry point, the node importance index and the attack cost measurement method are constructed. Thirdly, the identification of vulnerable nodes is transformed into the optimization problem of node combinatorial selection, and the vulnerable node identification method based on tabu search is proposed. Based on vulnerable nodes, a robustness enhancement strategy for aviation armament SoS network is presented. Finally, the above methods are used to an aerial confrontation SoS, and the results verify the rationality and effectiveness of the proposed methods.

A performance-driven framework with a system-of-systems approach for augmented asset management of railway system

The railway system is a complex technical system-of-systems (SoS). To address the complexity of the railway system, a holistic approach is needed that facilitates the development of an appropriate asset management regime. A systems-of-systems (SoS) approach considers the complex nature of the railway system, comprising interconnected subsystems like rolling stock and infrastructure. Neglecting these interdependencies risks sub-optimization of the overall system performance. Asset management of the railway system utilising a SoS approach ensures the focus of asset management on overall system requirements. The efficiency and effectiveness of the railway system is based on aspects such as availability, reliability, and safety performance. To enhance these aspects, monitoring, and improvement of key performance indicators (KPIs) emphasizing increased capacity and reduced operational costs is essential. The KPIs offer quantifiable parameters for performance optimization. Augmenting asset management through data-driven technologies can improve the efficiency and effectiveness of asset management. However, challenges persist in the implementation of data-driven solutions due to the railway system’s complexity and lack of a holistic perspective. A systematic performance-driven framework with a system-of-systems approach for augmented asset management of railway system provides handrail for the utilisation of data-driven technologies with railway system requirements at the centre while developing an asset management regime. The proposed framework aims to establish a clear relationship between system KPIs, and the performance of sub-systems and components aiding railway organizations in asset management design and implementation. This paper explains the important components of the proposed framework and demonstrates the application the framework for asset management and maintenance planning of high value components in the fleet of railway rolling stock. Adoption of the proposed framework is expected to enhance asset management through development and implementation of data-driven solutions that are aligned with system KPIs, to support asset management decision making.

A New Horizon for Healthcare Delivery: A System of Systems Perspective and Governing Proposition

AbstractThe healthcare system is grappling with inherent challenges, functioning akin to a fragmented cottage‐like industry, leading to significant cost implications and compromised care quality. This paper employs a systematic approach to scrutinize the Healthcare Delivery System (HDS) comprehensively, categorizing it as a Collaborative System of Systems (SoS), where multiple independent systems operate collectively, maintaining individual autonomy. Through a detailed examination, we identify the Collaborative SoS nature of the current healthcare system as the primary cause of its fragmentation. We address a gap in the current literature on the characteristics of SoS, focusing on the often‐overlooked aspect of dependence and exploring why constituent systems collaborate to achieve common objectives. Then, we propose a hybrid SoS model where an external governing entity at the national level assumes the authority to determine objectives and drivers for the healthcare SoS. We contend that effective SoS governance is indispensable for addressing systemic issues, providing necessary coordination, allocating resources, establishing policies, fostering sustainable change, and ensuring a well‐organized and efficient healthcare system.

Evaluating the Scalability and Combinatorial Effectiveness of Design‐for‐Resilience Heuristics

AbstractThis study investigates the scalability of biologically inspired design‐for‐resilience heuristics in System of Systems (SoS) of varying sizes, simulating SoS with ten, twenty, and thirty constituent systems. We build upon previous research that identified thirteen design heuristics for SoS resilience based on Ecological Network Analysis (a subset of graph theory). We both extend their application to larger network sizes and combine them to enhance efficiency. Our analysis validates the application of design heuristics for random networks to evaluate the effectiveness of individual and combined design heuristics in network resilience compared to random network modifications. The outcomes provide insights into the scalability and efficiency of these heuristics, revealing the potential for systematic SoS design and resilience improvement. Key contributions of this research include the validation of the scalability of bio‐inspired resilience metrics and the testing of nine new combined design heuristics for SoS. These contributions provide a tool for decision‐makers seeking to select resilient SoS architectures. The findings also pave the way for future research into broader applications beyond ecological networks and further exploration of the relationship between ecological robustness and resilience.

SoS ‐ Global Solutions to Global Problems Using UAF

AbstractThis paper applies Unified Architecture Framework (UAF) to a case study which defines the global copper market as an enterprise comprising a diverse set of stakeholders and independently operating businesses and industries, with the goal to understand how they might evaluate, execute, or modify their behaviors in response to the diminishing global copper supply. Specifically, we sought to determine if the framework viewpoints, modeling language, and workflow guidance provided in the UAF specification could support the analysis. In a true System of Systems (SoS), the solution (or any improvement) relies on the cooperation of a multitude of independent and unrelated businesses and industries. Several viewpoints of UAF were evaluated to model the SoS, which reveal how certain entities may be motivated to implement solutions, and how those decisions may impact others within the SoS. We also provide observations from the analysis which may serve to improve the utility of UAF in other applications.

Coupling Independent Solid Mechanics-Based Systems in a System-of-Systems Modeling Framework

Modularity is essential for ensuring the efficient execution of system-of-systems (SoS) frameworks, demanding the managerial and operational independence of constituent systems. This study explores the feasibility of enforcing displacement compatibility between two interconnected, independent solid mechanics finite element models with a contact interface within an SoS. This work developed an approach that ensures operational independence by delaying displacement compatibility in one of the systems. The lagged system provides a trial displacement input to the leading system, which determines the displacement discrepancy between both systems. This error is used to calculate an equivalent pressure that enforces displacement compatibility between the models. The method was verified by modeling two specimens with a frictionless contact interface and comparing the results against a continuous model assuming a perfect bond between the specimens. Lastly, the method was implemented within an SoS for space habitats and proved effective in ensuring matching displacements at the contact surface between two interacting structural layers. The proposed approach preserves the modularity of coupled systems, avoiding complex iterative procedures and transferring mass and stiffness information between systems. Moreover, it allows the coupled models to be developed in independent coordinate systems, as they only pass scalar, coordinate-independent parameters through the input–output ports.

Hyundai's Modular MBSE Approach to ‘Purpose Built Vehicle’ Architecture Development

AbstractThis paper discusses an ongoing effort at Hyundai to develop a model‐based systems engineering (MBSE) methodology for cross‐domain vehicle architecture development that is practical at the enterprise level. Our approach follows a modular modeling process that complements MBSE. In the age of smart mobility, automobile systems are indeed interdependent elements of a system of systems (SoS). Connectedness favors numerous mobility features that emerge due to the interfaces among these constituent systems. Managing emergent product line variations, changing consumer demands coupled with faster market response require manufacturers to modularize their architecture development processes. This can help scale MBSE across vehicle programs. This study proposes a modular system architecture approach for developing Hyundai's purpose‐built vehicle (PBV) concept that maintains a link to the legacy vehicle breakdown structures already in use. Using the Arcadia method, the ‘to‐be’ developed electric vehicle is expressed as a hierarchical functional partitioning of the subsystem modules. A physical architecture is defined as a solution to the functional partitioning based on an existing vehicle breakdown in a combined ‘top‐down/bottom‐up’ workflow thus capturing a realistic system decomposition. In the SoS hierarchy, the PBV is at the top level and is partitioned into multiple levels of nested subsystem architectures owned and developed by designated module teams in a distributed modeling environment. Results of the preliminary architecture modularization effort indicate significant potential for benefits over classical architecture modeling such as iterative knowledge capture, enhanced reusability across projects, products and programs, and distributed vehicle performance development across the extended MBSE enterprise, which includes the tier 1/2 suppliers.

Modeling Enterprise Software with UAF

AbstractSystems and Software Engineers often have an uneasy relationship. The job of the systems engineer is to work with the stakeholders to define a set of requirements that meet their needs. These are then allocated to various solution spaces such as electronic hardware, mechanical, procedural, and software among others. For many systems, the functional requirements are almost exclusively software requirements. Correspondingly, as an increasing amount of project manpower, schedule time, and budget are allocated to software, it becomes increasingly important that systems and software engineers communicate effectively. The Systems Modeling Language (SysML) has helped in this regard in that it can provide executable behavioral models with precise semantics to express software requirements in a model. These models define “What is required” without overly constraining the implementation. In addition, SysML can be used to define performance constraints, required concurrency, hardware memory and processor budgets, interfaces, safety critical requirements, etc. These aspects are essential for software engineers to understand the constraints and limitations of their environment. At the System of Systems (SoS)/Enterprise level, defining software/systems employs a similar pattern, but at a higher level of abstraction. In the Unified Architecture Framework, capabilities are defined for the enterprise, with systems and software allocated to realize the capabilities. In the same way that capabilities depend on one another, the implementing systems and software interact to support each other. In the past, enterprise software would be modeled as residing in mainframes in a federated software pattern. Modern software can be modeled throughout the enterprise in a distributed network that can adapt to the changing needs of the enterprise to do load leveling, dynamic and late binding, reconfiguration, and reallocation of hardware resources as necessary. If the domain includes the Industrial Internet of Things (IIOT), then deployment could include edge devices, embedded software, Programmable Logic Controllers (PLC), PCs, servers, cloud computing, and of course mainframes. The Object management Group (OMG) Data Distribution Services (DDS) standard enables these capabilities across these devices in a universal format implemented by multiple vendors. However, before this complex system of systems can be implemented, it must first be architected and designed to ensure that it will be fit for purpose both now and as the complex system of systems expands and evolves. This paper will examine the aspects of modeling software in the UAF, and how it can help guide enterprise and system and software architecture.

Securing Your Eggs in Multiple Baskets — Assuring a Resilient and Secure Supply Chain

AbstractThe global supply chain is a complex system of systems made up of and relying on other complex systems of systems (SoS) to achieve its goals. To take a typical example, Enterprise A is supplied essential parts on a regular basis to manufacture its products. To place the order requires global financial systems, integrated email systems, the internet, multiple telecommunications systems, and supply software provided by large companies. To deliver the parts may require air and maritime transportation systems, the rail network, interstate highway systems, road haulage companies, state and local transportation systems and so forth. When any of these complex systems fail, the impact can be global, and the results catastrophic. Recent examples include the shortage of Personal Protective Equipment (PPE) during the COVID pandemic, computer chip shortages delaying the assembly and sales of cars, and, most recently, the baby formula shortage. These were due to disruptions in the supply chain caused by an overreliance on single sourced suppliers who failed to deliver, transportation disruptions, outsourcing of critical parts, supplies, medicines to distant countries, and/or an overreliance on “Just In Time” for inventory management. This is the case of placing too many eggs in too few baskets, and often just one basket. Counterfeit or substandard parts and products can enter the supply chain via graft, breaks in chain of custody, or carelessness. This has included critical mechanical parts on aircraft, chips containing spyware, and substandard or out of date medicines substituted for the real thing resulting in serious illness and death. This complex SoS needs to be examined, studied, and understood in the same way as a mission critical system; threats, vulnerabilities, and risks need to be identified and mitigated and assurance cases defined to ensure a solid and reliable supply chain. This paper will look at the supply chain of an example factory system to determine how some of these problems can be predicted, prevented, mitigated, and solved using the UAF, RAAML and assurance case techniques.

Extending SysML Model Federation to Support Systems of Systems Multilevel Security Development

AbstractPractitioners of modern systems engineering within the defense industry and intelligence community often find themselves being pulled in diametrically opposed directions. On the one hand, systems engineering is quickly evolving into a digital practice, strategically connecting heterogeneous sets of models to form digital threads and digital twins capable of providing insights more valuable than the sum of their parts. On the other hand, the inherent nature of working within the national security space necessitates information be held a multiple levels of classification, safeguarded from release, and compartmentalized. This paper focuses on Model Based Systems Engineering (MBSE) development to introduce methods and tools to aid in overcoming these challenges. The work presented here builds on previously published works in SysML Model Federation for Systems of Systems (SoS) Architecting, the experience of applying this methodology on real world programs. Furthermore, it leverages freely available MBSE tools, processes, and methods in the construction of System Architecture Models (SAMs). This paper culminates in a call to action for additional published research and development to address residual challenges and gaps with respect to executing MBSE for Multilevel Security (MLS) development.

Looking back and forward: A retrospective and future directions on software engineering for systems‐of‐systems

AbstractModern systems are increasingly connected and more integrated with other existing systems, giving rise to systems‐of‐systems (SoS). An SoS consists of a set of independent, heterogeneous systems that interact to provide new functionalities and accomplish global missions through emergent behavior manifested at runtime. The distinctive characteristics of SoS, when contrasted to traditional systems, pose significant research challenges within software engineering. These challenges motivate the need for a paradigm shift and the exploration of novel approaches for designing, developing, deploying, and evolving these systems. The International Workshop on Software Engineering for Systems‐of‐Systems (SESoS) series started in 2013 to fill a gap in scientific forums addressing SoS from the software engineering perspective, becoming the first venue for this purpose. This article presents a study aimed at outlining the evolution and future trajectory of software engineering for SoS based on the examination of 57 papers spanning the 11 editions of the SESoS workshop (2013–2023). The study combined scoping review and scientometric analysis methods to categorize and analyze the research contributions concerning temporal and geographic distribution, topics of interest, research methodologies employed, application domains, and research impact. Based on such a comprehensive overview, this article discusses current and future directions in software engineering for SoS.

Characterizing the defense industry for risk management: a systems approach

PurposeManagement and risk techniques within industries have been studied from various disciplines in nondefense-affiliated industries. Given the assumption that these techniques, strategies and mitigations used in one industry apply to other similar industries, this paper examines the defense industry for risk assessment. We characterize interactions for onward application to risk identification in the defense industry.Design/methodology/approachThis research employs a systems theory approach to the characterization of industry interactions, using three dimensions including environment, boundaries and relationships. It develops a framework for identifying relationship types within system-of-systems (SoS) environments by analyzing the features of interactions that occur in such environments.FindingsThe study’s findings show that different systems environments within the defense industry SoS exhibit different interaction characteristics and hence display different relationship patterns, which can indicate potential vulnerabilities.Research limitations/implicationsBy employing interaction as a means for evaluating potential risks, this research emphasizes the role played by relationship factors in reducing perceived risks and simultaneously increasing trust.Originality/valueThis paper intends to develop an initial snapshot of the relationship status of the Swedish defense industry in light of the global consolidation in this industry, which is a relevant contextual contribution.

TSoSRA: A task-oriented resilience assessment framework for system-of-systems

System-of-systems (SoS) are inevitably subject to disturbances during task execution, and resilience is a key factor for SoS damage and recovery. System-of-systems resilience (SoSR) assessment holds significant value in optimizing SoS architecture and completing tasks. However, identifying the most resilient SoS among different ones for the same task is a basic but challenging question. This paper proposes a task-oriented SoSR assessment framework (TSoSRA) to identify the most resilient SoS. First, we use a heterogeneous information network and meta-path to describe a SoS network architecture composed of different subsystems and the SoS performance model is developed, based on node and link quality. Based on this model, a system-of-system resilience metric (SoSRM) is proposed to describe the ability of the SoS to recover quickly dealing with disruption. Then, we extend further this metric to consider the impact of mitigation measures that exist in practical scenarios. Finally, we demonstrate the feasibility and effectiveness of TSoSRA through a case study, offering valuable insights to enhance network security, improve SoS reliability and design a more resilient SoS.

AI Concepts for System of Systems Dynamic Interoperability.

Interoperability is a central problem in digitization and System of Systems (SoS) engineering, which concerns the capacity of systems to exchange information and cooperate. The task to dynamically establish interoperability between heterogeneous cyber-physical systems (CPSs) at run-time is a challenging problem. Different aspects of the interoperability problem have been studied in fields such as SoS, neural translation, and agent-based systems, but there are no unifying solutions beyond domain-specific standardization efforts. The problem is complicated by the uncertain and variable relations between physical processes and human-centric symbols, which result from, e.g., latent physical degrees of freedom, maintenance, re-configurations, and software updates. Therefore, we surveyed the literature for concepts and methods needed to automatically establish SoSs with purposeful CPS communication, focusing on machine learning and connecting approaches that are not integrated in the present literature. Here, we summarize recent developments relevant to the dynamic interoperability problem, such as representation learning for ontology alignment and inference on heterogeneous linked data; neural networks for transcoding of text and code; concept learning-based reasoning; and emergent communication. We find that there has been a recent interest in deep learning approaches to establishing communication under different assumptions about the environment, language, and nature of the communicating entities. Furthermore, we present examples of architectures and discuss open problems associated with artificial intelligence (AI)-enabled solutions in relation to SoS interoperability requirements. Although these developments open new avenues for research, there are still no examples that bridge the concepts necessary to establish dynamic interoperability in complex SoSs, and realistic testbeds are needed.

Principles for the design of system of systems exemplified using modularisation

AbstractIn the context of system of systems (SoS) engineering, the incorporation of design principles is critical to guide the engineering process. This paper presents a systematic literature review to synthesize a list of principles tailored for SoS. 26 principles were identified as generic principles and 39 were mapped to the specific challenges in SoS engineering. Through an evaluation using the principle of modularisation in the design of a charging infrastructure, the study offers insights into the real-world effectiveness of these principles, showing their relevance in SoS engineering tasks.