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  • 1.
    Ashraf, Adnan
    et al.
    Abo Akad Univ, Fac Sci & Engn, Turku, Finland..
    Majd, Amin
    Abo Akad Univ, Fac Sci & Engn, Turku, Finland..
    Troubitsyna, Elena
    KTH, School of Electrical Engineering and Computer Science (EECS), Computer Science, Theoretical Computer Science, TCS.
    Online Path Generation and Navigation for Swarms of UAVs2020In: Scientific Programming, ISSN 1058-9244, E-ISSN 1875-919X, Vol. 2020, article id 8530763Article in journal (Refereed)
    Abstract [en]

    With the growing popularity of unmanned aerial vehicles (UAVs) for consumer applications, the number of accidents involving UAVs is also increasing rapidly. Therefore, motion safety of UAVs has become a prime concern for UAV operators. For a swarm of UAVs, a safe operation cannot be guaranteed without preventing the UAVs from colliding with one another and with static and dynamically appearing, moving obstacles in the flying zone. In this paper, we present an online, collision-free path generation and navigation system for swarms of UAVs. The proposed system uses geographical locations of the UAVs and of the successfully detected, static, and moving obstacles to predict and avoid the following: (1) UAV-to-UAV collisions, (2) UAV-to-static-obstacle collisions, and (3) UAV-to-moving-obstacle collisions. Our collision prediction approach leverages efficient runtime monitoring and complex event processing (CEP) to make timely predictions. A distinctive feature of the proposed system is its ability to foresee potential collisions and proactively find best ways to avoid predicted collisions in order to ensure safety of the entire swarm. We also present a simulation-based implementation of the proposed system along with an experimental evaluation involving a series of experiments and compare our results with the results of four existing approaches. The results show that the proposed system successfully predicts and avoids all three kinds of collisions in an online manner. Moreover, it generates safe and efficient UAV routes, efficiently scales to large-sized problem instances, and is suitable for cluttered flying zones and for scenarios involving high risks of UAV collisions.

  • 2. Loni, M.
    et al.
    Majd, A.
    Loni, A.
    Daneshtalab, M.
    Sjödin, M.
    Troubitsyna, Elena
    KTH, School of Electrical Engineering and Computer Science (EECS).
    Designing compact convolutional neural network for embedded stereo vision systems2018In: Proceedings - 2018 IEEE 12th International Symposium on Embedded Multicore/Many-Core Systems-on-Chip, MCSoC 2018, Institute of Electrical and Electronics Engineers (IEEE), 2018, p. 244-251, article id 8540240Conference paper (Refereed)
    Abstract [en]

    Autonomous systems are used in a wide range of domains from indoor utensils to autonomous robot surgeries and self-driving cars. Stereo vision cameras probably are the most flexible sensing way in these systems since they can extract depth, luminance, color, and shape information. However, stereo vision based applications suffer from huge image sizes and computational complexity leading system to higher power consumption. To tackle these challenges, in the first step, GIMME2 stereo vision system [1] is employed. GIMME2 is a high-throughput and cost efficient FPGA-based stereo vision embedded system. In the next step, we present a framework for designing an optimized Deep Convolutional Neural Network (DCNN) for time constraint applications and/or limited resource budget platforms. Our framework tries to automatically generate a highly robust DCNN architecture for image data receiving from stereo vision cameras. Our proposed framework takes advantage of a multi-objective evolutionary optimization approach to design a near-optimal network architecture for both the accuracy and network size objectives. Unlike recent works aiming to generate a highly accurate network, we also considered the network size parameters to build a highly compact architecture. After designing a robust network, our proposed framework maps generated network on a multi/many core heterogeneous System-on-Chip (SoC). In addition, we have integrated our framework to the GIMME2 processing pipeline such that it can also estimate the distance of detected objects. The generated network by our framework offers up to 24x compression rate while losing only 5% accuracy compare to the best result on the CIFAR-10 dataset.

  • 3. Rauf, I.
    et al.
    Vistbakka, I.
    Troubitsyna, Elena
    KTH, School of Electrical Engineering and Computer Science (EECS), Theoretical Computer Science, TCS.
    Formal Verification of Stateful Services with REST APIs Using Event-B2018In: Proceedings - 2018 IEEE International Conference on Web Services, ICWS 2018 - Part of the 2018 IEEE World Congress on Services, Institute of Electrical and Electronics Engineers Inc. , 2018, p. 131-138Conference paper (Refereed)
    Abstract [en]

    REST APIs are being increasingly used in the industry including their application in safety-critical domain and in the IoT world. They offer basic CRUD (create, retrieve, update and delete) interfaces. However, REST APIs can be used to build services with more advanced scenarios. Developing such services with REST constraints requires rigorous approaches that are capable of creating services that can be trusted for their behavior. In this work, we present an approach based on formal verification technique for a development of REST services using Event-B. We focus on deriving a correct system architecture by refinement and consistency verification of service design models. We illustrate our approach on a Hotel Reservation System. 

  • 4.
    Rauf, Irum
    et al.
    Open Univ, Ctr Res Comp, Milton Keynes, Bucks, England..
    Troubitsyna, Elena
    KTH, School of Electrical Engineering and Computer Science (EECS), Theoretical Computer Science, TCS.
    Porres, Ivan
    Abo Akad Univ, Dept Informat Technol, Turku, Finland..
    A systematic mapping study of API usability evaluation methods2019In: Computer Science Review, ISSN 1574-0137, E-ISSN 1876-7745, Vol. 33, p. 49-68Article, review/survey (Refereed)
    Abstract [en]

    An Application Programming Interface (API) provides a programmatic interface to a software component that is often offered publicly and may be used by programmers who are not the API's original designers. APIs play a key role in software reuse. By reusing high quality components and services, developers can increase their productivity and avoid costly defects. The usability of an API is a qualitative characteristic that evaluates how easy it is to use an API. Recent years have seen a considerable increase in research efforts aiming at evaluating the usability of APIs. An API usability evaluation can identify problem areas and provide recommendations for improving the API. In this systematic mapping study, we focus on 47 primary studies to identify the aim and the method of the API usability studies. We investigate which API usability factors are evaluated, at which phases of API development is the usability of API evaluated and what are the current limitations and open issues in API usability evaluation. We believe that the results of this literature review would be useful for both researchers and industry practitioners interested in investigating the usability of API and new API usability evaluation methods.

  • 5.
    Troubitsyna, Elena
    et al.
    KTH.
    Rauf, Irum
    Generating cloud monitors from models to secure clouds2018In: Proceedings - 48th Annual IEEE/IFIP International Conference on Dependable Systems and Networks, DSN 2018, Institute of Electrical and Electronics Engineers (IEEE), 2018, p. 526-533, article id 8416512Conference paper (Refereed)
    Abstract [en]

    Authorization is an important security concern in cloud computing environments. It aims at regulating an access of the users to system resources. A large number of resources associated with REST APIs typical in cloud makes an implementation of security requirements challenging and error-prone. To alleviate this problem, in this paper we propose an implementation of security cloud monitor. We rely on model-driven approach to represent the functional and security requirements. Models are then used to generate cloud monitors. The cloud monitors contain contracts used to automatically verify the implementation. We use Django web framework to implement cloud monitor and OpenStack to validate our implementation.

  • 6.
    Troubitsyna, Elena
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Theoretical Computer Science, TCS.
    Vistbakka, Inna
    Abo Akad Univ, Turku, Finland..
    Deriving and Formalising Safety and Security Requirements for Control Systems2018In: COMPUTER SAFETY, RELIABILITY, AND SECURITY (SAFECOMP 2018) / [ed] Gallina, B Skavhaug, A Bitsch, F, SPRINGER INTERNATIONAL PUBLISHING AG , 2018, p. 107-122Conference paper (Refereed)
    Abstract [en]

    Safety-critical control systems become increasingly open and interconnected. However, there is still a lack of the techniques that enable an integrated analysis of safety and security requirements. In this paper, we propose an approach that allows the designers to derive and formalise safety and security requirements in a structured systematic way. To elicit both types of the requirements, we adapt and integrate traditional safety and security analysis techniques. To formally specify and verify them, we rely on Event-B framework. The framework allows us to develop a complex specification of system behaviour in presence of both accidental faults and security attacks and analyse mutual interdependencies between safety and security requirements.

  • 7. Vistbakka, I.
    et al.
    Barash, M.
    Troubitsyna, Elena
    KTH, School of Electrical Engineering and Computer Science (EECS), Theoretical Computer Science, TCS. Åbo Akademi University, Turku, Finland.
    Towards creating a DSL facilitating modelling of dynamic access control in event-B2018In: 6th International Conference on ABZ Conference on ASM, Alloy, B, TLA, VDM, and Z, ABZ 2018, Springer, 2018, Vol. 10817, p. 386-391Conference paper (Refereed)
    Abstract [en]

    Role-Based Access Control (RBAC) is a popular authorization model used to manage resource-access constraints in a wide range of systems. The standard RBAC framework adopts a static, state-independent approach to define the access rights to the system resources. It is often insufficient for correct implementation of the desired functionality and should be augmented with the dynamic, i.e., a state-dependant view on the access control. In this paper, we present a work in progress on creating a domain-specific language and the tool support for modelling and verification of dynamic RBAC. They support a tabular representation of the static RBAC constraints together with the graphical model of the scenarios and enable an automated translation of them into an Event-B model.

  • 8. Vistbakka, I.
    et al.
    Majd, A.
    Troubitsyna, Elena
    KTH, School of Electrical Engineering and Computer Science (EECS), Theoretical Computer Science, TCS.
    Deriving mode logic for autonomous resilient systems2018In: 20th International Conference on Formal Engineering Methods, ICFEM 2018, Springer Verlag , 2018, p. 320-336Conference paper (Refereed)
    Abstract [en]

    Ensuring system resilience – dependability in presence of changes – is a complex engineering task. To achieve resilience, a system should not only autonomously cope with non-deterministically changing internal state and external operating conditions but also proactively reconfigure to maintain efficiency. To facilitate structuring and verifying such complex system behavior, in this paper, we demonstrate how to derive resilience-enhancing mode transition logic from the goals that the system should achieve. Our approach is formalised in Event-B that allows us to reason about resilience mechanisms at different architectural levels. We illustrate the proposed approach by an example – safe and efficient navigation of a swarm of drones. 

  • 9. Vistbakka, I.
    et al.
    Majd, A.
    Troubitsyna, Elena
    KTH, School of Electrical Engineering and Computer Science (EECS). Åbo Akademi University, Turku, Finland.
    Multi-layered approach to safe navigation of swarms of drones2018In: Workshops: ASSURE, DECSoS, SASSUR, STRIVE, and WAISE 2018 co-located with 37th International Conference on Computer Safety, Reliability and Security, SAFECOMP 2018, Springer, 2018, Vol. 11094, p. 112-125Conference paper (Refereed)
    Abstract [en]

    Swarms of drones are complex distributed systems that should operate safely, i.e., avoid collisions with each other and unforeseen objects appearing in the flight zones. Ensuring safety of drone navigation is challenging due to unreliability of drones, communication channels and non-determinism of the operating environment. In this paper, we propose a novel multi-layered approach to ensuring safety of drone navigation. It aims at maintaining an optimal ratio between efficiency of mission execution and safety at a hierarchical distributed way. We formalise the proposed approach in Event-B and derive the coordination and reconfiguration mechanisms ensuring efficiency and safety of mission execution.

  • 10. Vistbakka, I.
    et al.
    Troubitsyna, Elena
    KTH, School of Electrical Engineering and Computer Science (EECS), Theoretical Computer Science, TCS.
    Modelling and verification of dynamic role-based access control2018In: 12th International Conference on Verification and Evaluation of Computer and Communication Systems, VECoS 2018, Springer, 2018, Vol. 11181, p. 48-63Conference paper (Refereed)
    Abstract [en]

    Controlling access to resources is essential for ensuring correctness of system functioning. Role-Based Access Control (RBAC) is a popular authorisation model that regulates the user’s rights to manage system resources based on the user’s role. In this paper, we extend the traditional static approach to defining RBAC and propose as well as formalise a dynamic RBAC model. It allows a designer to explicitly define the dependencies between the system states and permissions to access and modify system resources. To facilitate a systematic description and verification of the dynamic access rights, we propose a contract-based approach and then we demonstrate how to model and verify dynamic RBAC in Event-B. The approach is illustrated by a case study – a reporting management system. 

  • 11. Vistbakka, I.
    et al.
    Troubitsyna, Elena
    KTH, School of Electrical Engineering and Computer Science (EECS), Computer Science, Theoretical Computer Science, TCS. Åbo Akademi University, Turku, Finland.
    Pattern-based formal approach to analyse security and safety of control systems2019In: 6th International Symposium on Model-Based Safety and Assessment, IMBSA 2019, Springer, 2019, Vol. 11842, p. 363-378Conference paper (Refereed)
    Abstract [en]

    Increased openness and interconnectedness of safety-critical control systems calls for techniques enabling an integrated analysis of safety and security requirements. Often safety and security requirements have intricate interdependencies that should be uncovered and analysed in a structured and rigorous way. In this paper, we propose an approach that facilitates a systematic derivation and formalisation of safety and security requirements. We propose the specification and refinement patterns in Event-B that allow us to specify and verify system behaviour and properties in the presence of both accidental faults and security attacks and analyse interdependencies between safety and security requirements.

  • 12. Vistbakka, I.
    et al.
    Troubitsyna, Elena
    KTH, School of Electrical Engineering and Computer Science (EECS), Theoretical Computer Science, TCS.
    Towards a Formal Approach to Analysing Security of Safety-Critical Systems2018In: Proceedings - 2018 14th European Dependable Computing Conference, EDCC 2018, Institute of Electrical and Electronics Engineers Inc. , 2018, p. 182-189Conference paper (Refereed)
    Abstract [en]

    Since safety-critical control systems become increasingly interconnected, there is a clear need for the techniques that enable an integrated analysis of safety and security requirements. In this paper, we propose an integrated approach to systematically deriving and formalising safety and security requirements. To facilitate requirements elicitation, we propose to adapt and integrate traditional safety and security analysis techniques. To formally specify and verify the requirements, we rely on Event-B framework. By relying on refinement and proofs, the framework allows us to specify and verify system behaviour in presence of both accidental faults and security attacks and analyse mutual interdependencies between safety and security requirements.

  • 13.
    Vistbakka, Inna
    et al.
    Abo Akad Univ, Informat Technol, Turku, Finland..
    Troubitsyna, Elena
    KTH, School of Electrical Engineering and Computer Science (EECS), Theoretical Computer Science, TCS. KTH Royal Inst Technol, Dept Theoret Comp Sci, Stockholm, Sweden..
    Majd, Amin
    Abo Akad Univ, Informat Technol, Turku, Finland..
    Multi-Layered Safety Architecture of Autonomous Systems: Formalising Coordination Perspective2019In: 201919TH IEEE INTERNATIONAL SYMPOSIUM ON HIGH ASSURANCE SYSTEMS ENGINEERING (HASE 2019) / [ed] Yu, D Nguyen, V Jiang, C, IEEE , 2019, p. 58-65Conference paper (Refereed)
    Abstract [en]

    A pressure to deploy autonomous systems in real life is increasing. Since exhaustive verification of safety of autonomous systems is unfeasible, the emphasis should be put on safety optimisation and run-time safety-monitoring techniques. In this paper, we propose a multi-layered architecture of autonomous systems. We define the notions of strategic, tactic and active safety the complementary mechanisms for achieving safety. We take a swarm of drones as an example and formally define a multi-layered safety architecture and associated coordination mechanisms and underlying communication model to implement the defined complementary safety mechanisms. The derived coordination logic and communication model is formalised in Event-B framework.

  • 14. Vistbakka, l.
    et al.
    Troubitsyna, Elena
    KTH, School of Electrical Engineering and Computer Science (EECS), Computer Science, Theoretical Computer Science, TCS.
    Modelling Autonomous Resilient Multi-robotic Systems2019In: 11th International Workshop on Software Engineering for Resilient Systems, SERENE 2019, Springer Verlag , 2019, p. 29-45Conference paper (Refereed)
    Abstract [en]

    Resilience is an ability of the system to deliver its services in a dependable way despite the changes. In this paper, we propose a multi-agent based formal outlook on ensuring resilience of multi-robotic systems. We represent system functions as collaborative activities performed by the agents with different capabilities. Changes invoke either structural reconfigurations – forming different collaborations or compensative activities – introducing into the system agents with additional capabilities. We formalize the resilience mechanisms and demonstrate their use by a case study – a coordination of a swarm of drones.

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