ASAS: An Approach to Support Simulation of Smart Systems

Smart systems, such as smart cities, smart buildings, and autonomous cars, have recently gained increasing popularity. Each such system is essentially a System-of-Systems (SoS). SoS are dynamically established as alliances among independent and heterogeneous software systems to offer complex functionalities as a result of constituents interoperability. An SoS often supports critical application domains, and, as such, must be reliable. Many SoS have been specified and evaluated for their correct operation using static models. However, speciï¬cation languages have not supported to capture their inherent dynamic nature nor enabled to monitor their operation. The main contribution of this paper is to present ASAS, an approach to Automatically generate Simulation models for smArt Systems (ASAS) in order to support evaluation of their operation. In particular, our approach makes it possible to transform formal models of the SoS architecture (expressed in SoSADL) into simulation models (expressed in DEVS). We evaluated our approach by conducting two case studies using a flood monitoring system that is intended to be part of a smart city. Results indicate that ASAS can successfully generate functional simulations for the SoS operation, which in turn can enable to reason and monitor an SoS operation, taking into account its dynamic nature

S.O.B (Save Our Budget) - A Simulation-Based Method for Prediction of Acquisition Costs of Constituents of a System-of-Systems

Software economics, acquisition, and pricing are important concerns for Systems-of-Systems (SoS). SoS are alliances of independent software-intensive systems combined to offer holistic functionalities as a result of the constituents interoperability. SoS engineering involves separately acquiring constituents and combining them to form the SoS. Despite the existence of cost prediction techniques, predicting SoS acquisition costs at design-time should also include the analysis of different suppliers of constituents, their respective prices and quality. However, known methods cover only two out of these three parameters.  The main contribution of this article is to present the S.O.B. (Save Our Budget) method, a novel simulation-based method to predict, at design-time, the acquisition cost of constituents, while still considering quality attributes and different suppliers. Results of a case study in the Smart Building domain revealed that S.O.B. method supports a precise prediction of acquisition cost of constituents to build a SoS for that domain. Furthermore, it also contributes to estimate the cost based on a pre-established quality attribute (functional suitability), as well as to support the selection of coalition that exhibits better results through the analysis of cost-benefit ratio.Software economics, acquisition, and pricing are important concerns for Systems-of-Systems (SoS). SoS are alliances of independent software-intensive systems combined to offer holistic functionalities as a result of the constituents interoperability. SoS engineering involves separately acquiring constituents and combining them to form the SoS. Despite the existence of cost prediction techniques, predicting SoS acquisition costs at design-time should also include the analysis of different suppliers of constituents, their respective prices and quality. However, known methods cover only two out of these three parameters. The main contribution of this article is to present the S.O.B. (Save Our Budget) method, a novel simulation-based method to predict, at design-time, the acquisition cost of constituents, while still considering quality attributes and different suppliers. Results of a case study in the Smart Building domain revealed that S.O.B. method supports a precise prediction of acquisition cost of constituents to build a SoS for that domain. Furthermore, it also contributes to estimate the cost based on a pre-established quality attribute (functional suitability), as well as to support the selection of coalition that exhibits better results through the analysis of cost-benefit ratio

SAM-SoS: A stochastic software architecture modeling and verification approach for complex System-of-Systems

A System-of-Systems (SoS) is a complex, dynamic system whose Constituent Systems (CSs) are not known precisely at design time, and the environment in which they operate is uncertain. SoS behavior is unpredictable due to underlying architectural characteristics such as autonomy and independence. Although the stochastic composition of CSs is vital to achieving SoS missions, their unknown behaviors and impact on system properties are unavoidable. Moreover, unknown conditions and volatility have significant effects on crucial Quality Attributes (QAs) such as performance, reliability and security. Hence, the structure and behavior of a SoS must be modeled and validated quantitatively to foresee any potential impact on the properties critical for achieving the missions. Current modeling approaches lack the essential syntax and semantics required to model and verify SoS behaviors at design time and cannot offer alternative design choices for better design decisions. Therefore, the majority of existing techniques fail to provide qualitative and quantitative verification of SoS architecture models. Consequently, we have proposed an approach to model and verify Non-Deterministic (ND) SoS in advance by extending the current algebraic notations for the formal models as a hybrid stochastic formalism to specify and reason architectural elements with the required semantics. A formal stochastic model is developed using a hybrid approach for architectural descriptions of SoS with behavioral constraints. Through a model-driven approach, stochastic models are then translated into PRISM using formal verification rules. The effectiveness of the approach has been tested with an end-to-end case study design of an emergency response SoS for dealing with a fire situation. Architectural analysis is conducted on the stochastic model, using various qualitative and quantitative measures for SoS missions. Experimental results reveal critical aspects of SoS architecture model that facilitate better achievement of missions and QAs with improved design, using the proposed approach

A Delphi study to recognize and assess systems of systems vulnerabilities

Context: System of Systems (SoS) is an emerging paradigm by which independent systems collaborate by sharing resources and processes to achieve objectives that they could not achieve on their own. In this context, a number of emergent behaviors may arise that can undermine the security of the constituent systems. Objective: We apply the Delphi method with the aims to improve our understanding of SoS security and related problems, and to investigate their possible causes and remedies. Method: Experts on SoS expressed their opinions and reached consensus in a series of rounds by following a structured questionnaire. Results: The results show that the experts found more consensus in disagreement than in agreement about some SoS characteristics, and on how SoS vulnerabilities could be identified and prevented. Conclusions: From this study we learn that more work is needed to reach a shared understanding of SoS vul nerabilities, and we leverage expert feedback to outline some future research directions.Ministerio de Ciencia, Innovación y Universidades PID2019-105455GB-C3

Formally Describing the Architectural Behavior of Software-Intensive Systems-of-Systems with SosADL

International audienceSoftware-intensive systems are often independently developed, operated, managed, and evolved. Progressively, communication networks have enabled these independent systems to interact, yielding a new kind of complex system, i.e. a system that is itself composed of systems, the so-called System-of-Systems (SoS). By its complex nature, SoS exhibits emergent behaviors. Nowadays, none of the Architecture Description Languages (ADLs), which have been developed for modeling the architectural behavior of single software-intensive systems, has the expressive power to formally describe the architectural behavior of Software-intensive SoSs. For addressing this research challenge, we propose a novel ADL, called SosADL, specially conceived for formally describing the architecture of Software-intensive SoSs. It embodies SoS architectural concepts and constructs encompassing the formal description of software architectures from both the structural and behavioral viewpoints. This paper presents SosADL focusing on the description of the architectural behavior of Software-intensive SoSs. It describes SosADL from its behavioral viewpoint enabling to specify independent systems, mediators among these systems, coalitions of mediated systems, and the architectural conditions that enforce the production of emergent SoS behaviors. It illustrates SosADL through an excerpt of a real application for architecting a Flood Monitoring and Emergency Response SoS