Cyber-Physical Systems, as distributed systems of computational elements interacting with the physical world, are highly complex systems. They can, in many instances, be considered safety critical interactive systems, as errors in interaction can have disastrous consequences (consider the case of autonomous vehicles or integrated clinical environments). High assurance is, then, an underlying requirement, also at their user interface. In this position paper we identify five challenges to be solved both in the short and in the long term, regarding the modelling of (1) distributed and (2) heterogeneous interactive systems, (3) the analysis and relation between the different abstraction layers of Cyber-Physical Systems, (4) the modelling of real time/hybrid systems, and (5) the modelling of the dynamic nature of such systems. Solutions for these challenges are not presented, but possible directions are discussed.This  work  was  financed  by  National  Funds  through  the  Portuguese  fundingagency,  FCT  -  Fundação  para  a  Ciência  e  a  Tecnologia  (Portuguese  Foundation for Science and Technology) within project: UID/EEA/50014/201

Campos, José C.

Couto, Rui

Information Technology and Nanotechnology

English

Universidade do Minho: RepositoriUM

High Assurance on Cyber-Physical InteractiveSystemsRui Couto[0000−0002−9214−3767] and José C. Campos[0000−0001−9163−580X]Department of Informatics/University of Minho & HASLab/INESC TECBraga, Portugal{rui.couto, jose.campos}@di.uminho.ptAbstract. Cyber-Physical Systems, as distributed systems of compu-tational elements interacting with the physical world, are highly com-plex systems. They can, in many instances, be considered safety criticalinteractive systems, as errors in interaction can have disastrous conse-quences (consider the case of autonomous vehicles or integrated clinicalenvironments). High assurance is, then, an underlying requirement, alsoat their user interface. In this position paper we identify five challengesto be solved both in the short and in the long term, regarding the mod-elling of (1) distributed and (2) heterogeneous interactive systems, (3) theanalysis and relation between the different abstraction layers of Cyber-Physical Systems, (4) the modelling of real time/hybrid systems, and (5)the modelling of the dynamic nature of such systems. Solutions for thesechallenges are not presented, but possible directions are discussed.Keywords: Cyber-Physical Systems, Interactive Systems, Formal Meth-ods1 Modelling and verifying Cyber-Physical SystemsCyber-Physical Systems (CPS) are networked and/or distributed systems of computational elements interacting with physical processes in feedback loops. CPS are composed of heterogeneous elements, some of which might support in-teraction with users (humans) through different means, from traditional graph-ical user interfaces to different types of sensors. In these cases, we can consider them to have humans in the loop, as part of the systems themselves. Exam-ples include autonomous driving vehicles and Integrated Clinical Environments (ICE) (see [13] for a state of the art). These are also two examples of systems that require some degree of user interaction to operate.According to Accord Market, the global market share of CPS has reached the order of million US$ in 2018, and its further expansion is expected [6]. CPS such as Advanced Driver-Assistance Systems (ADAS) or autonomous driving vehicles, which aim not only to improve the driving experience, but also to increase driving and road safety, are being pushed forward by market demands. These demands have raised a set of challenges to be addressed in the short term [11], as these systems are already in usage. Solving these challenges is of major relevance, asCopyright © 2019 for this paper by its authors. Use permitted under Creative Commons License Attribution 4.0 International (CC BY 4.0).2 Rui Couto and José C. Camposthe occurrence of errors has serious consequences, such as incidents occurringwith autonomous driving vehicles1.In [10] a number of challenges related to developing user interfaces for CPSis identified, from the lack of standardized interaction hardware, to appropriatedevelopment process and tools. Here, however, we focus specifically on the designanalysis aspect. In particular, when the need to assure the safety of the systems ispresent. Many of these systems can be considered critical (interactive) systems,as they allow the users to perform potentially dangerous actions. Due to theircomplex nature, their verification is far from a trivial process. Intuitively, it ispossible to understand that adding multiple communicating devices will furtherincrease the complexity of the analysis process, when compared with traditionalsystems.Model-based approaches allow developers to create models describing thesystems to be analyzed, in which (semi-)automated analysis approaches can beapplied, such as model checking or theorem proving (i.e. formal verification meth-ods). CPS, being complex systems, require appropriate modelling and verifica-tion techniques, in order to reduce the possibility of error. Formal model-basedverification approaches for CPS have been discussed, both in terms of challengesand of concrete proposals for analysis. General challenges are discussed in [14],while [12] discusses challenges expected in modelling autonomous driving ve-hicles. Concrete proposals include model-based analysis, but also co-simulationand testing [4], as well as proposals for anomaly detection [5]. These works focusmainly in the modelling of the behavior and intercommunication aspects, butlack consideration of the human-computer interaction angle. This paper high-lights the challenges related with model-based approaches applied to the userinteraction aspects of these systems.In the case of interactive systems, model-based approaches have also been de-veloped to verify interaction properties. An example is the IVY workbench [1],which provides a language to specify interactive systems, a compiler to sup-port the verification of the language with the NuSMV model checker [2] andvisualizations to present the analysis result, as well as simulation features. ThePVSIO-web tool [8] presents a different approach, both in the formal analy-sis process, which resorts to the PVS theorem prover [9], and in the supportfor model inspection, providing tools that support building prototypes from themodels. The CIRCUS tool suite [3] supports the modeling of interactive systems,with an emphasis in task modelling and analysis. An effort was made to pro-vide tools which support the modelling process, at different abstraction levels. Ingeneral, current approaches focus mainly in the validation of single user-systeminteractions. However, interaction in CPS is not provided by a single interface,but rather by different computational elements.1 https://www.tesla.com/blog/what-we-know-about-last-weeks-accident, lastvisited July 15, 2019.High Assurance on Cyber-Physical Interactive Systems 32 Modelling and verification challengesAn initial exploration has been done in [7], regarding the interactive componentsof CPS in the context of ICE systems, which already provides some understand-ing of the expected challenges. While the authors explored the adoption of ex-isting techniques to handle CPS, the challenge itself is bigger than just applyingexisting approaches, multiplied by the number of communicating devices, plusa communication challenge. Thus, regarding the application of model-based ap-proaches to the interactive components of CPS, five main challenges are expectedto be faced:Distributed interactive systems — The nature of CPS implies the exis-tence of distributed (interactive) systems, and consequently distributed in-terfaces of systems cooperating between themselves. This results in the chal-lenge of modelling those systems and interfaces, but more interestingly, inmodelling their properties. We need to understand what is specific aboutthem and how it can be specified, and which properties can be specifiedand/or verified. Such requires investigating appropriate languages and tools.Heterogeneous interactive systems — CPS are composed of several de-vices, which can interact with users through distinct approaches, such asgraphical user interfaces, physical elements (e.g. buttons), or motion sen-sors. The heterogeneity of the resulting user interfaces can, ultimately, leadto the need to create different modelling approaches, in order to support, forinstance, analysis and prototyping. Further research is required in the CPScontext.Different abstraction levels — CPS can be specified at different specifica-tion levels, as, for instance, the device layer, the communication layer, andthe network layer. As user interfaces are built on top of these layers, theiranalysis can ultimately be affected by the capability of analyzing each ofthe layers. While this increases the complexity of modelling these systems,it increases the complexity of their analysis as well. Considering the chal-lenges imposed by CPS, existing tools and approaches should be analyzedin this context, in order to understand their suitability to address each ofthese layers.Modelling real time/hybrid systems — Due to the critically of these kindsof systems, the application of real time verification techniques is expected.Such can easily become an issue, since current verification techniques presentscalability issues. Furthermore, the computational components are typicallydiscrete in nature, while the physical process are continuous. As a result,how best to model and analyze the real time and hybrid dimensions of userinterfaces for CPS, and their relevant properties, needs to be investigated.Dynamic systems — CPS are prone to changes in the network, with the in-clusion/removal of nodes. An example is Vehicle-to-Vehicle (V2V) communi-cation, where vehicles constantly enter and exit the range of other vehicles.Thus, the existence of a specific vehicle in the system is not guaranteed.The same is true for an ICE system, where devices can be added/remove as4 Rui Couto and José C. Camposwell. Thus, the dynamic aspect of the network should be taken in considera-tion. This is expected to impact the behavior of the interactive systems, andconsequently, how they are modelled.3 ConclusionModel-based approaches have been successfully used to improve the reliability ofsoftware systems, as well as of interactive systems. The dissemination of CPS hasraised new concerns, currently not addressed by existing solutions. This positionpaper described five challenges that are expected to be found while developingnew approaches for modeling and dealing with user interfaces for CPS. Facingthem, ultimately requires researchers to combine the previous acquired knowl-edge in model-based approaches and CPS, in order to develop new approaches.AcknowledgmentsThis work was financed by National Funds through the Portuguese fundingagency, FCT - Fundação para a Ciência e a Tecnologia (Portuguese Founda-tion for Science and Technology) within project: UID/EEA/50014/2019.References1. Campos, J.C., Harrison, M.D.: Interaction engineering using the IVY tool. In: Pro-ceedings of the 1st ACM SIGCHI symposium on Engineering interactive computingsystems. pp. 35–44. ACM (2009)2. Cimatti, A., Clarke, E., Giunchiglia, E., Giunchiglia, F., Pistore, M., Roveri, M.,Sebastiani, R., Tacchella, A.: NuSMV Version 2: An OpenSource Tool for SymbolicModel Checking. In: Proc. International Conference on Computer-Aided Verifica-tion (CAV 2002). LNCS, vol. 2404. Springer, Copenhagen, Denmark (July 2002)3. Fayollas, C., Martinie, C., Palanque, P., Deleris, Y., Fabre, J.C., Navarre, D.: Anapproach for assessing the impact of dependability on usability: application tointeractive cockpits. In: 2014 Tenth European Dependable Computing Conference.pp. 198–209. IEEE (2014)4. Fitzgerald, J., Gamble, C., Larsen, P.G., Pierce, K., Woodcock, J.: Cyber-PhysicalSystems Design: Formal Foundations, Methods and Integrated Tool Chains. In:2015 IEEE/ACM 3rd FME Workshop on Formal Methods in Software Engineering.pp. 40–46 (May 2015). https://doi.org/10.1109/FormaliSE.2015.145. Jones, A., Kong, Z., Belta, C.: Anomaly detection in cyber-physical systems: Aformal methods approach. In: 53rd IEEE Conference on Decision and Control. pp.848–853 (Dec 2014). https://doi.org/10.1109/CDC.2014.70394876. Market, A.: Global cyber-physical system (cps) market by product type and byend-users/application global market share, forecast data, in-depth analysis, anddetailed overview, and forecast, 2013 2026. Tech. rep., Apex Market Research(2019)High Assurance on Cyber-Physical Interactive Systems 57. Masci, P., Mallozzi, P., De Angelis, F.L., Serugendo, G.D.M., Curzon, P.: UsingPVSio-web and SAPERE for rapid prototyping of user interfaces in IntegratedClinical Environments. In: Verisure2015, Workshop on Verification and Assurance,co-located with CAV2015 (2015)8. Masci, P., Oladimeji, P., Zhang, Y., Jones, P., Curzon, P., Thimbleby, H.: PVSio-web 2.0: Joining PVS to HCI. In: International Conference on Computer AidedVerification. pp. 470–478. Springer (2015)9. Owre, S., Rushby, J.M., , Shankar, N.: PVS: A prototype verification system. In:Kapur, D. (ed.) 11th International Conference on Automated Deduction (CADE).Lecture Notes in Artificial Intelligence, vol. 607, pp. 748–752. Springer-Verlag,Saratoga, NY (jun 1992), http://www.csl.sri.com/papers/cade92-pvs/10. Paelke, V., Röcker, C.: User interfaces for cyber-physical systems: Challenges andpossible approaches. In: Marcus, A. (ed.) Design, User Experience, and Usabil-ity: Design Discourse. Lecture Notes in Computer Science, vol. 9186, pp. 75–85.Springer (2015)11. Romanovsky, A., Ishikawa, F.: Trustworthy cyber-physical systems engineering.CRC Press (2016)12. Seshia, S.A., Sadigh, D., Sastry, S.S.: Formal methods for semi-autonomous driv-ing. In: 2015 52nd ACM/EDAC/IEEE Design Automation Conference (DAC).pp. 1–5 (June 2015). https://doi.org/10.1145/2744769.274792713. Torngreen, M., Bensalem, S., Cengarle, M.V., Chen, D.J., McDermid, J.,Passerone, R., Sangiovanni-Vincentelli, A., Runkler, T.: CPS: state of the art.Deliverable D5.1, CyPhERS (Cyber-Physical European Roadmap and Strategy)project (2014)14. Zheng, X., Julien, C.: Verification and Validation in Cyber Physical Systems: Re-search Challenges and a Way Forward. In: 2015 IEEE/ACM 1st InternationalWorkshop on Software Engineering for Smart Cyber-Physical Systems. pp. 15–18.IEEE (May 2015). https://doi.org/10.1109/SEsCPS.2015.11

High assurance on cyber-physical interactive systems

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High assurance on cyber-physical interactive systems

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