Change search
Refine search result
12345 1 - 50 of 244
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 1.
    Abbas, Zainab
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Software and Computer systems, SCS.
    Al-Shishtawy, Ahmad
    RISE SICS, Stockholm, Sweden.
    Girdzijauskas, Sarunas
    KTH, School of Electrical Engineering and Computer Science (EECS), Software and Computer systems, SCS. RISE SICS, Stockholm, Sweden..
    Vlassov, Vladimir
    KTH, School of Electrical Engineering and Computer Science (EECS), Software and Computer systems, SCS.
    Short-Term Traffic Prediction Using Long Short-Term Memory Neural Networks2018Conference paper (Refereed)
    Abstract [en]

    Short-term traffic prediction allows Intelligent Transport Systems to proactively respond to events before they happen. With the rapid increase in the amount, quality, and detail of traffic data, new techniques are required that can exploit the information in the data in order to provide better results while being able to scale and cope with increasing amounts of data and growing cities. We propose and compare three models for short-term road traffic density prediction based on Long Short-Term Memory (LSTM) neural networks. We have trained the models using real traffic data collected by Motorway Control System in Stockholm that monitors highways and collects flow and speed data per lane every minute from radar sensors. In order to deal with the challenge of scale and to improve prediction accuracy, we propose to partition the road network into road stretches and junctions, and to model each of the partitions with one or more LSTM neural networks. Our evaluation results show that partitioning of roads improves the prediction accuracy by reducing the root mean square error by the factor of 5. We show that we can reduce the complexity of LSTM network by limiting the number of input sensors, on average to 35% of the original number, without compromising the prediction accuracy.

  • 2. Ahmed, J.
    et al.
    Johnsson, A.
    Moradi, F.
    Pasquini, R.
    Flinta, C.
    Stadler, Rolf
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Online approach to performance fault localization for cloud and datacenter services2017In: Proceedings of the IM 2017 - 2017 IFIP/IEEE International Symposium on Integrated Network and Service Management, Institute of Electrical and Electronics Engineers Inc. , 2017, p. 873-874Conference paper (Refereed)
    Abstract [en]

    Automated detection and diagnosis of the performance faults in cloud and datacenter environments is a crucial task to maintain smooth operation of different services and minimize downtime. We demonstrate an effective machine learning approach based on detecting metric correlation stability violations (CSV) for automated localization of performance faults for datacenter services running under dynamic load conditions. © 2017 IFIP.

  • 3. Ahmed, J.
    et al.
    Johnsson, A.
    Yanggratoke, Rerngvit
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. KTH, School of Electrical Engineering (EES), Communication Networks.
    Ardelius, J.
    Flinta, C.
    Stadler, Rolf
    KTH, School of Electrical Engineering (EES), Communication Networks. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Predicting SLA conformance for cluster-based services using distributed analytics2016In: Proceedings of the NOMS 2016 - 2016 IEEE/IFIP Network Operations and Management Symposium, IEEE conference proceedings, 2016, p. 848-852Conference paper (Refereed)
    Abstract [en]

    Service assurance for the telecom cloud is a challenging task and is continuously being addressed by academics and industry. One promising approach is to utilize machine learning to predict service quality in order to take early mitigation actions. In previous work we have shown how to predict service-level metrics, such as frame rate for a video application on the client side, from operational data gathered at the server side. This gives the service provider early indications on whether the platform can support the current load demand. This paper extends previous work by addressing scalability issues for cluster-based services. Operational data being generated in large volumes, from several sources, and at high velocity puts strain on computational and communication resources. We propose and evaluate a distributed machine learning system based on the Winnow algorithm to tackle scalability issues, and then compare the new distributed solution with the previously proposed centralized solution. We show that network overhead and computational execution time is substantially reduced while maintaining high prediction accuracy making it possible to achieve real-time service quality predictions in large systems.

  • 4. Ahmed, J.
    et al.
    Josefsson, T.
    Johnsson, A.
    Flinta, C.
    Moradi, F.
    Pasquini, R.
    Stadler, Rolf
    KTH, School of Electrical Engineering and Computer Science (EECS), Network and Systems engineering. KTH, School of Electrical Engineering and Computer Science (EECS), Centres, ACCESS Linnaeus Centre.
    Automated diagnostic of virtualized service performance degradation2018In: IEEE/IFIP Network Operations and Management Symposium: Cognitive Management in a Cyber World, NOMS 2018, Institute of Electrical and Electronics Engineers Inc. , 2018, p. 1-9Conference paper (Refereed)
    Abstract [en]

    Service assurance for cloud applications is a challenging task and is an active area of research for academia and industry. One promising approach is to utilize machine learning for service quality prediction and fault detection so that suitable mitigation actions can be executed. In our previous work, we have shown how to predict service-level metrics in real-time just from operational data gathered at the server side. This gives the service provider early indications on whether the platform can support the current load demand. This paper provides the logical next step where we extend our work by proposing an automated detection and diagnostic capability for the performance faults manifesting themselves in cloud and datacenter environments. This is a crucial task to maintain the smooth operation of running services and minimizing downtime. We demonstrate the effectiveness of our approach which exploits the interpretative capabilities of Self- Organizing Maps (SOMs) to automatically detect and localize different performance faults for cloud services. © 2018 IEEE.

  • 5.
    Alferez, Mauricio
    et al.
    Univ Luxembourg, Interdisciplinary Ctr Secur Reliabil & Trust SnT, 2 Ave JF Kennedy, L-1855 Luxembourg, Luxembourg..
    Acher, Mathieu
    Univ Rennes, DiverSE Team Inria Rennes, IRISA, CNRS, Rennes, France..
    Galindo, Jose A.
    Univ Seville, Dept Comp Languages & Syst, Seville, Spain..
    Baudry, Benoit
    KTH, School of Electrical Engineering and Computer Science (EECS), Software and Computer systems, SCS.
    Benavides, David
    Univ Seville, Dept Comp Languages & Syst, Seville, Spain..
    Modeling variability in the video domain: language and experience report2019In: Software quality journal, ISSN 0963-9314, E-ISSN 1573-1367, Vol. 27, no 1, p. 307-347Article in journal (Refereed)
    Abstract [en]

    In an industrial project, we addressed the challenge of developing a software-based video generator such that consumers and providers of video processing algorithms can benchmark them on a wide range of video variants. This article aims to report on our positive experience in modeling, controlling, and implementing software variability in the video domain. We describe how we have designed and developed a variability modeling language, called VM, resulting from the close collaboration with industrial partners during 2 years. We expose the specific requirements and advanced variability constructs; we developed and used to characterize and derive variations of video sequences. The results of our experiments and industrial experience show that our solution is effective to model complex variability information and supports the synthesis of hundreds of realistic video variants. From the software language perspective, we learned that basic variability mechanisms are useful but not enough; attributes and multi-features are of prior importance; meta-information and specific constructs are relevant for scalable and purposeful reasoning over variability models. From the video domain and software perspective, we report on the practical benefits of a variability approach. With more automation and control, practitioners can now envision benchmarking video algorithms over large, diverse, controlled, yet realistic datasets (videos that mimic real recorded videos)-something impossible at the beginning of the project.

  • 6.
    Apolonia, Nuno
    et al.
    Universitat Politecnica de Catalunya (UPC) Barcelona, Spain.
    Antaris, Stefanos
    Girdzijauskas, Šarunas
    KTH, School of Electrical Engineering and Computer Science (EECS), Software and Computer systems, SCS.
    Pallis, G.
    Dikaiakos, Marios
    SELECT: A distributed publish/subscribe notification system for online social networks2018In: Proceedings - 2018 IEEE 32nd International Parallel and Distributed Processing Symposium, IPDPS 2018, Institute of Electrical and Electronics Engineers (IEEE), 2018, p. 970-979, article id 8425250Conference paper (Refereed)
    Abstract [en]

    Publish/subscribe (pub/sub) mechanisms constitutean attractive communication paradigm in the design of large-scale notification systems for Online Social Networks (OSNs). Toaccommodate the large-scale workloads of notifications producedby OSNs, pub/sub mechanisms require thousands of serversdistributed on different data centers all over the world, incurringlarge overheads. To eliminate the pub/sub resources used, wepropose SELECT - a distributed pub/sub social notificationsystem over peer-to-peer (P2P) networks. SELECT organizesthe peers on a ring topology and provides an adaptive P2Pconnection establishment algorithm where each peer identifiesthe number of connections required, based on the social structureand user availability. This allows to propagate messages to thesocial friends of the users using a reduced number of hops.The presented algorithm is an efficient heuristic to an NP-hard problem which maps workload graphs to structured P2Poverlays inducing overall, close to theoretical, minimal number ofmessages. Experiments show that SELECT reduces the numberof relay nodes up to 89% versus the state-of-the-art pub/subnotification systems. Additionally, we demonstrate the advantageof SELECT against socially-aware P2P overlay networks andshow that the communication between two socially connectedpeers is reduced on average by at least 64% hops, while achieving100% communication availability even under high churn.

  • 7.
    Apolonia, Nuno
    et al.
    KTH, School of Information and Communication Technology (ICT). Universitat Politecnica de Catalunya (UPC) Barcelona, Spain.
    Freitag, Felix
    Universitat Politècnica de Catalunya. Barcelona, Spain.
    Navarro, Leandro
    Universitat Politècnica de Catalunya, BarcelonaTECH, Barcelona, Spain.
    Girdzijauskas, Sarunas
    KTH, School of Electrical Engineering and Computer Science (EECS), Software and Computer systems, SCS.
    Socially aware microcloud service overlay optimization in community networks2019In: Software, practice & experience, ISSN 0038-0644, Vol. 49, no 1, article id 13Article in journal (Refereed)
    Abstract [en]

    Community networks are a growing network cooperation effort by citizens to build and maintain Internet infrastructure in regions that are not available. Adding that, to bring cloud services to community networks (CNs), microclouds were started as an edge cloud computing model where members cooperate using resources. Therefore, enhancing routing for services in CNs is an attractive paradigm that benefits the infrastructure. The problem is the growing consumption of resources for disseminating messages in the CN environment. This is because the services that build their overlay networks are oblivious to the underlying workload patterns that arise from social cooperation in CNs. In this paper, we propose Select in Community Networks (SELECTinCN), which enhances the overlay creation for pub/sub systems over peer‐to‐peer (P2P) networks. Moreover, SELECTinCN includes social information based on cooperation within CNs by exploiting the social aspects of the community of practice. Our work organizes the peers in a ring topology and provides an adaptive P2P connection establishment algorithm, where each peer identifies the number of connections needed based on the social structure and user availability. This allows us to propagate messages using a reduced number of hops, thus providing an efficient heuristic to an NP‐hard problem that maps the workload graph to the structured P2P overlays resulting in a number of messages close to the theoretical minimum. Experiments show that, by using social network information, SELECTinCN reduces the number of relay nodes by up to 89% using the community of practice information versus the state‐of‐the‐art pub/sub notification systems given as baseline.

  • 8. Artho, Cyrille
    et al.
    Gros, Quentin
    Rousset, Guillaume
    Precondition Coverage in Software Testing2016In: Proc. 1st Int. Workshop on Validating Software Tests (VST 2016), IEEE conference proceedings, 2016Conference paper (Refereed)
    Abstract [en]

    Preconditions indicate when it is permitted to use a given function. However, it is not always the case that both outcomes of a precondition are observed during testing. A precondition that is always false makes a function unusable, a precondition that is always true may turn out to be actually an invariant. In model-based testing, preconditions describes when a transition may be executed from a given state. If no outgoing transition is enabled in a given state because all preconditions of all outgoing transitions are false, the test model may be flawed. Experiments show a low test coverage of preconditions in the Scala library. We also investigate preconditions in Modbat models for model-based testing, in that case, a certain number of test cases is needed to produce sufficient coverage, but remaining cases of low coverage indeed point to legitimate flaws in test models or code.

  • 9.
    Artho, Cyrille
    et al.
    KTH, School of Computer Science and Communication (CSC). National Institute of Advanced Industrial Science and Technology (AIST), Japan.
    Gros, Quentin
    Rousset, Guillaume
    Banzai, Kazuaki
    Ma, Lei
    Kitamura, Takashi
    Hagiya, Masami
    Tanabe, Yoshinori
    Yamamoto, Mitsuharu
    Model-based API Testing of Apache ZooKeeper2017In: 2017 10TH IEEE INTERNATIONAL CONFERENCE ON SOFTWARE TESTING, VERIFICATION AND VALIDATION (ICST), IEEE , 2017, p. 288-298Conference paper (Refereed)
    Abstract [en]

    Apache ZooKeeper is a distributed data storage that is highly concurrent and asynchronous due to network communication; testing such a system is very challenging. Our solution using the tool "Modbat" generates test cases for concurrent client sessions, and processes results from synchronous and asynchronous callbacks. We use an embedded model checker to compute the test oracle for non-deterministic outcomes; the oracle model evolves dynamically with each new test step. Our work has detected multiple previously unknown defects in ZooKeeper. Finally, a thorough coverage evaluation of the core classes show how code and branch coverage strongly relate to feature coverage in the model, and hence modeling effort.

  • 10. Artho, Cyrille
    et al.
    Ma, Lei
    Classification of Randomly Generated Test Cases2016In: Proc. 1st Int. Workshop on Validating Software Tests (VST 2016), IEEE conference proceedings, 2016Conference paper (Refereed)
    Abstract [en]

    Random test case generation produces relatively diverse test sequences, but the validity of the test verdict is always uncertain. Because tests are generated without taking the specification and documentation into account, many tests are invalid. To understand the prevalent types of successful and invalid tests, we present a classification of 56 issues that were derived from 208 failed, randomly generated test cases. While the existing workflow successfully eliminated more than half of the tests as irrelevant, half of the remaining failed tests are false positives. We show that the new @NonNull annotation of Java 8 has the potential to eliminate most of the false positives, highlighting the importance of machine-readable documentation.

  • 11.
    Artho, Cyrille
    et al.
    KTH, School of Computer Science and Communication (CSC), Theoretical Computer Science, TCS.
    Olveczky, Peter Csaba
    Formal Techniques for Safety-Critical Systems (FTSCS 2014) Preface2017In: Science of Computer Programming, ISSN 0167-6423, E-ISSN 1872-7964, Vol. 133, p. 89-90Article in journal (Other academic)
  • 12. Artho, Cyrille
    et al.
    Rousset, Guillaume
    Model-based Testing of the Java network API2017In: Electronic Proceedings in Theoretical Computer Science, ISSN 2075-2180, E-ISSN 2075-2180, no 245, p. 46-51Article in journal (Refereed)
    Abstract [en]

    Testing networked systems is challenging. The client or server side cannot be tested by itself. We present a solution using tool "Modbat" that generates test cases for Java's network library java.nio, where we test both blocking and non-blocking network functions. Our test model can dynamically simulate actions in multiple worker and client threads, thanks to a carefully orchestrated design that covers non-determinism while ensuring progress.

  • 13.
    Artho, Cyrille
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Theoretical Computer Science, TCS.
    Visser, W.
    Java Pathfinder at SV-COMP 2019 (Competition Contribution)2019In: 25th International Conference on Tools and Algorithms for the Construction and Analysis of Systems conference series, TACAS 2019 held as part of the 22nd European Joint Conferences on Theory and Practice of Software, ETAPS 2019, Springer, 2019, Vol. 11429, p. 224-228Conference paper (Refereed)
    Abstract [en]

    This paper gives a brief overview of Java Pathfinder, or jpf-core. We describe the architecture of JPF, its strengths, and how it was set up for SV-COMP 2019.

  • 14.
    Artho, Cyrille
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Theoretical Computer Science, TCS.
    Ölveczky, P.C.
    Formal Techniques for Safety-Critical Systems (FTSCS 2015)2018In: Science of Computer Programming, ISSN 0167-6423, E-ISSN 1872-7964, Vol. 154, p. 1-2Article in journal (Refereed)
  • 15.
    Artho, Cyrille
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Theoretical Computer Science, TCS.
    Ölveczky, P.C.
    Formal Techniques for Safety-Critical Systems (FTSCS 2016)2019In: Science of Computer Programming, ISSN 0167-6423, E-ISSN 1872-7964, Vol. 175, p. 35-36Article in journal (Refereed)
  • 16.
    Artho, Cyrille
    et al.
    KTH.
    Ölveczky, P.C.
    Preface2017In: 5th International Workshop on Formal Techniques for Safety-Critical Systems, FTSCS 2016, Springer Verlag , 2017Conference paper (Refereed)
  • 17. Ashjaei, Mohammad
    et al.
    Moghaddami Khalilzad, Nima
    KTH.
    Mubeen, Saad
    Behnam, Moris
    Sander, Ingo
    Almeida, Luis
    Nolte, Thomas
    Designing end-to-end resource reservations in predictable distributed embedded systems2017In: Real-time systems, ISSN 0922-6443, E-ISSN 1573-1383, Vol. 53, no 6, p. 916-956Article in journal (Refereed)
  • 18. Attarzadeh-Niaki, S. -H
    et al.
    Altinel, E.
    KTH.
    Koedam, M.
    Molnos, A.
    Sander, Ingo
    KTH.
    Goossens, K.
    A composable and predictable MPSoC design flow for multiple real-time applications2016In: Model-Implementation Fidelity in Cyber Physical System Design, Springer International Publishing , 2016, p. 157-174Chapter in book (Other academic)
    Abstract [en]

    Design of real-time MPSoC systems including multiple applications is challenging because temporal requirements of each application must be respected throughout the entire design flow. Currently the design of different applications is often interdependent, making converge to a solution for each application difficult. This chapter proposes a compositional method to design applications independently, and then to execute them without interference. We define a formal modeling framework as a suitable entry point for application design. The models are executable, which enables early detection of specification errors, and include the formal properties of the applications based on well-defined models of computation. We combine this with a predictable MPSoC platform template that has a supporting design flow but lacks a simulation front-end. The structure and behavior of the application models are exported to an intermediate format via introspection which is iteratively transformed for the backend flow. We identify the problems arising in this transformation and provide appropriate solutions. The design flow is demonstrated by a system consisting of two streaming applications where less than half of the design time is dedicated to operating on the integrated system model.

  • 19. Attarzadeh-Niaki, S. -H
    et al.
    Sander, Ingo
    KTH, School of Information and Communication Technology (ICT), Electronics.
    Automatic construction of models for analytic system-level design space exploration problems2017In: Proceedings of the 2017 Design, Automation and Test in Europe, DATE 2017, Institute of Electrical and Electronics Engineers (IEEE), 2017, p. 670-673, article id 7927074Conference paper (Refereed)
    Abstract [en]

    Due to the variety of application models and also the target platforms used in embedded electronic system design, it is challenging to formulate a generic and extensible analytic design-space exploration (DSE) framework. Current approaches support a restricted class of application and platform models and are difficult to extend. This paper proposes a framework for automatic construction of system-level DSE problem models based on a coherent, constraint-based representation of system functionality, flexible target platforms, and binding policies. Heterogeneous semantics is captured using constraints on logical clocks. The applicability of this method is demonstrated by constructing DSE problem models from different combinations of application and platforms models. Time-triggered and untimed models of the system functionality and heterogeneous target platforms are used for this purpose. Another potential advantage of this approach is that constructed models can be solved using a variety of standard and ad-hoc solvers and search heuristics.

  • 20.
    Attarzadeh-Niaki, Seyed-Hosein
    et al.
    KTH, School of Information and Communication Technology (ICT), Electronic Systems.
    Sander, Ingo
    KTH, School of Information and Communication Technology (ICT), Electronic Systems.
    An extensible modeling methodology for embedded and cyber-physical system design2016In: Simulation (San Diego, Calif.), ISSN 0037-5497, E-ISSN 1741-3133, Vol. 92, no 8, p. 771-794Article in journal (Refereed)
    Abstract [en]

    models are important tools to manage the increasing complexity of system design. The choice of a modeling language for constructing models governs what types of systems can be modeled, and which subsequent design activities can be performed. This is especially true for the area of embedded electronic and cyber-physical system design, which poses several challenging requirements of modeling and design methodologies. This article argues that the Formal System Design (ForSyDe) methodology with the necessary presented extensions fulfills these requirements, and thus qualifies for the design of tomorrow's systems. Based on the theory of models of computation and the concept of process constructors, heterogeneous models are captured in ForSyDe with formal semantics. A refined layer of the formalism is introduced to make its denotational-style semantics easy to implement on top of commonly used imperative languages, and an open-source realization on top of the IEEE standard language SystemC is presented. The introspection mechanism is introduced to automatically export an intermediate representation of the constructed models for further analysis/synthesis by external tools. Flexibility and extensibility of ForSyDe is emphasized by integrating a new timed model of computation without central synchronization, and by providing mechanisms for integrating foreign models, parallel and distributed simulation, modeling adaptive, data-parallel, and non-deterministic systems. A set of ForSyDe features is demonstrated in practice, and compared with similar approaches using a running example and two relevant case studies.

  • 21.
    Bahri, Leila
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Software and Computer systems, SCS.
    Girdzijauskas, Sarunas
    KTH, School of Electrical Engineering and Computer Science (EECS), Software and Computer systems, SCS.
    Blockchain technology: Practical P2P computing (Tutorial)2019In: Proceedings - 2019 IEEE 4th International Workshops on Foundations and Applications of Self* Systems, FAS*W 2019, Institute of Electrical and Electronics Engineers (IEEE), 2019, p. 249-250, article id 8791982Conference paper (Refereed)
    Abstract [en]

    Blockchain technology comes with the promise to revolutionize the way current IT systems are organized as well as to revise how trust is perceived in the wider society. In spite of the wide attention that cyrpto-currencies (such as Bitcoin) have attracted, Blockchain technology is more likely to make an impact beyond ongoing speculations on cyrpto-currencies. Decentralized identity management, transparent supply-chain systems, and IoT governance and security are only few examples of research challenges for which this technology may hold substantial potential. Blockchain technology has emerged at the intersection of two well established research areas: peer-to-peer (P2P) computing and cryptography. In this tutorial, we provide a general overview of the main components behind this technology, we present the difference between the types of Blockchain available today, and we make a high level discussion on its potentials and limitations as well as possible research challenges.

  • 22.
    Bahri, Leila
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Software and Computer systems, SCS.
    Girdzijauskas, Sarunas
    KTH, School of Electrical Engineering and Computer Science (EECS), Software and Computer systems, SCS.
    Trust Mends Blockchains: Living up to Expectations2019In: IEEE 39th International Conference on Distributed Computing Systems (ICDCS), Dallas, July 7-10 2019, 2019Conference paper (Refereed)
    Abstract [en]

    At the heart of Blockchains is the trustless leader election mechanism for achieving consensus among pseudoanonymous peers, without the need of oversight from any third party or authority whatsoever. So far, two main mechanisms are being discussed: proof-of-work (PoW) and proof-of-stake (PoS). PoW relies on demonstration of computational power, and comes with the markup of huge energy wastage in return of the stake in cyrpto-currency. PoS tries to address this by relying on owned stake (i.e., amount of crypto-currency) in the system. In both cases, Blockchains are limited to systems with financial basis. This forces non-crypto-currency Blockchain applications to resort to “permissioned” setting only, effectively centralizing the system. However, non-crypto-currency permisionless blockhains could enable secure and self-governed peer-to-peer structures for numerous emerging application domains, such as education and health, where some trust exists among peers. This creates a new possibility for valuing trust among peers and capitalizing it as the basis (stake) for reaching consensus. In this paper we show that there is a viable way for permisionless non-financial Blockhains to operate in completely decentralized environments and achieve leader election through proof-of-trust (PoT). In our PoT construction, peer trust is extracted from a trust network that emerges in a decentralized manner and is used as a waiver for the effort to be spent for PoW, thus dramatically reducing total energy expenditure of the system. Furthermore, our PoT construction is resilient to the risk of small cartels monopolizing the network (as it happens with the mining-pool phenomena in PoW) and is not vulnerable to sybils. We evluate security guarantees, and perform experimental evaluation of our construction, demonstrating up to 10-fold energy savings compared to PoW without trading off any of the decentralization characteristics, with further guarantees against risks of monopolization.

  • 23.
    Bahri, Leila
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Software and Computer systems, SCS.
    Girdzijauskas, Sarunas
    KTH, School of Electrical Engineering and Computer Science (EECS), Software and Computer systems, SCS.
    When Trust Saves Energy - A Reference Framework for Proof-of-Trust (PoT) Blockchains2018In: WWW '18 Companion Proceedings of the The Web Conference 2018, ACM Digital Library, 2018, p. 1165-1169Conference paper (Refereed)
    Abstract [en]

    Blockchains are attracting the attention of many technical, financial, and industrial parties, as a promising infrastructure for achieving secure peer-to-peer (P2P) transactional systems. At the heart of blockchains is proof-of-work (PoW), a trustless leader election mechanism based on demonstration of computational power. PoW provides blockchain security in trusless P2P environments, but comes at the expense of wasting huge amounts of energy. In this research work, we question this energy expenditure of PoW under blockchain use cases where some form of trust exists between the peers. We propose a Proof-of-Trust (PoT) blockchain where peer trust is valuated in the network based on a trust graph that emerges in a decentralized fashion and that is encoded in and managed by the blockchain itself. This trust is then used as a waiver for the difficulty of PoW; that is, the more trust you prove in the network, the less work you do.

  • 24. Bahri, Leila
    et al.
    Soliman, Amira
    KTH, School of Information and Communication Technology (ICT), Software and Computer systems, SCS.
    Squillaci, Jacopo
    Carminati, Barbara
    Ferrari, Elena
    Girdzijauskas, Sarunas
    KTH, School of Information and Communication Technology (ICT), Software and Computer systems, SCS.
    Beat the DIVa: Decentralized Identity Validation for Online Social Networks2016In: 2016 32ND IEEE INTERNATIONAL CONFERENCE ON DATA ENGINEERING (ICDE), 2016, p. 1330-1333Conference paper (Refereed)
    Abstract [en]

    Fake accounts in online social networks (OSNs) have known considerable sophistication and are now attempting to gain network trust by infiltrating within honest communities. Honest users have limited perspective on the truthfulness of new online identities requesting their friendship. This facilitates the task of fake accounts in deceiving honest users to befriend them. To address this, we have proposed a model that learns hidden correlations between profile attributes within OSN communities, and exploits them to assist users in estimating the trustworthiness of new profiles. To demonstrate our method, we suggest, in this demo, a game application through which players try to cheat the system and convince nodes in a simulated OSN to befriend them. The game deploys different strategies to challenge the players and to reach the objectives of the demo. These objectives are to make participants aware of how fake accounts can infiltrate within their OSN communities, to demonstrate how our suggested method could aid in mitigating this threat, and to eventually strengthen our model based on the data collected from the moves of the players.

  • 25.
    Balliu, Musard
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Computer Science, Theoretical Computer Science, TCS.
    Bastys, Iulia
    Chalmers Univ Technol, Dept Comp Sci & Engn, Gothenburg, Sweden..
    Sabelfeld, Andrei
    Chalmers Univ Technol, Dept Comp Sci & Engn, Gothenburg, Sweden..
    Securing IoT Apps2019In: IEEE Security and Privacy, ISSN 1540-7993, E-ISSN 1558-4046, Vol. 17, no 5, p. 22-29Article in journal (Refereed)
    Abstract [en]

    Users increasingly rely on Internet of Things (IoT) apps to manage their digital lives through the overwhelming diversity of IoT services and devices. Are the IoT app platforms doing enough to protect the privacy and security of their users? By securing IoT apps, how can we help users reclaim control over their data?

  • 26.
    Balliu, Musard
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Theoretical Computer Science, TCS.
    Merro, Massimo
    University of Verona.
    Pasqua, Michele
    University of Verona.
    Securing Cross-App Interactions in IoT Platforms2019Conference paper (Refereed)
    Abstract [en]

    IoT platforms enable users to connect various smart devices and online services via reactive apps running on the cloud. These apps, often developed by third-parties, perform simple computations on data triggered by external information sources and actuate the results of computation on external information sinks. Recent research shows that unintended or malicious interactions between the different (even benign) apps of a user can cause severe security and safety risks. These works leverage program analysis techniques to build tools for unveiling unexpected interference across apps for specific use cases. Despite these initial efforts, we are still lacking a semantic framework for understanding interactions between IoT apps. The question of what security policy cross-app interference embodies remains largely unexplored. This paper proposes a semantic framework capturing the essence of cross-app interactions in IoT platforms. The framework generalizes and connects syntactic enforcement mechanisms to bisimulation-based notions of security, thus providing a baseline for formulating soundness criteria of these enforcement mechanisms. Specifically, we present a calculus that models the behavioral semantics of a system of apps executing concurrently, and use it to define desirable semantic policies in the security and safety context of IoT apps. To demonstrate the usefulness of our framework, we define static mechanisms for enforcing crossapp security and safety, and prove them sound with respect to our semantic conditions. Finally, we leverage real-world apps to validate the practical benefits of our policy framework.

  • 27.
    Barbette, Tom
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Computer Science, Communication Systems, CoS, Network Systems Laboratory (NS Lab).
    Katsikas, Georgios P.
    KTH, School of Electrical Engineering and Computer Science (EECS), Computer Science, Communication Systems, CoS, Network Systems Laboratory (NS Lab).
    Maguire Jr., Gerald Q.
    KTH, School of Electrical Engineering and Computer Science (EECS), Computer Science, Communication Systems, CoS, Radio Systems Laboratory (RS Lab).
    Kostic, Dejan
    KTH, School of Electrical Engineering and Computer Science (EECS), Computer Science, Communication Systems, CoS.
    RSS++: load and state-aware receive side scaling2019In: Proceedings of the 15th International Conference on emerging Networking EXperiments and Technologies / [ed] ACM, Orlando, FL, USA: Association for Computing Machinery (ACM), 2019Conference paper (Refereed)
    Abstract [en]

    While the current literature typically focuses on load-balancing among multiple servers, in this paper, we demonstrate the importance of load-balancing within a single machine (potentially with hundreds of CPU cores). In this context, we propose a new load-balancing technique (RSS++) that dynamically modifies the receive side scaling (RSS) indirection table to spread the load across the CPU cores in a more optimal way. RSS++ incurs up to 14x lower 95th percentile tail latency and orders of magnitude fewer packet drops compared to RSS under high CPU utilization. RSS++ allows higher CPU utilization and dynamic scaling of the number of allocated CPU cores to accommodate the input load, while avoiding the typical 25% over-provisioning. RSS++ has been implemented for both (i) DPDK and (ii) the Linux kernel. Additionally, we implement a new state migration technique, which facilitates sharding and reduces contention between CPU cores accessing per-flow data. RSS++ keeps the flow-state by groups that can be migrated at once, leading to a 20% higher efficiency than a state of the art shared flow table.

  • 28.
    Barbosa, Fernando S.
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Robotics, Perception and Learning, RPL.
    Duberg, Daniel
    KTH, School of Electrical Engineering and Computer Science (EECS), Robotics, Perception and Learning, RPL.
    Jensfelt, Patric
    KTH, School of Electrical Engineering and Computer Science (EECS), Robotics, Perception and Learning, RPL.
    Tumova, Jana
    KTH, School of Electrical Engineering and Computer Science (EECS), Robotics, Perception and Learning, RPL.
    Guiding Autonomous Exploration with Signal Temporal Logic2019In: IEEE Robotics and Automation Letters, ISSN 2377-3766, E-ISSN 1949-3045, Vol. 4, no 4, p. 3332-3339Article in journal (Refereed)
    Abstract [en]

    Algorithms for autonomous robotic exploration usually focus on optimizing time and coverage, often in a greedy fashion. However, obstacle inflation is conservative and might limit mapping capabilities and even prevent the robot from moving through narrow, important places. This letter proposes a method to influence the manner the robot moves in the environment by taking into consideration a user-defined spatial preference formulated in a fragment of signal temporal logic (STL). We propose to guide the motion planning toward minimizing the violation of such preference through a cost function that integrates the quantitative semantics, i.e., robustness of STL. To demonstrate the effectiveness of the proposed approach, we integrate it into the autonomous exploration planner (AEP). Results from simulations and real-world experiments are presented, highlighting the benefits of our approach.

  • 29.
    Barbosa, Fernando S.
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Intelligent systems, Robotics, Perception and Learning, RPL.
    Lindemann, Lars
    KTH, School of Electrical Engineering and Computer Science (EECS), Intelligent systems, Decision and Control Systems (Automatic Control).
    Dimarogonas, Dimos V.
    KTH, School of Electrical Engineering and Computer Science (EECS), Intelligent systems, Decision and Control Systems (Automatic Control).
    Tumova, Jana
    KTH, School of Electrical Engineering and Computer Science (EECS), Intelligent systems, Robotics, Perception and Learning, RPL.
    Integrated motion planning and control under metric interval temporal logic specifications2019In: 2019 18th European Control Conference, ECC 2019, Institute of Electrical and Electronics Engineers (IEEE), 2019, p. 2042-2049, article id 8795925Conference paper (Refereed)
    Abstract [en]

    This paper proposes an approach that combines motion planning and hybrid feedback control design in order to find and follow trajectories fulfilling a given complex mission involving time constraints. We use Metric Interval Temporal Logic (MITL) as a rich and rigorous formalism to specify such missions. The solution builds on three main steps: (i) using sampling-based motion planning methods and the untimed version of the mission specification in the form of Zone automaton, we find a sequence of waypoints in the workspace; (ii) based on the clock zones from the satisfying run on the Zone automaton, we compute time-stamps at which these waypoints should be reached; and (iii) to control the system to connect two waypoints in the desired time, we design a low-level feedback controller leveraging Time-varying Control Barrier Functions. Illustrative simulation results are included.

  • 30.
    Bastys, Iulia
    et al.
    Chalmers University of Technology.
    Balliu, Musard
    KTH, School of Computer Science and Communication (CSC), Theoretical Computer Science, TCS.
    Sabelfeld, Andrei
    Chalmers University of Technology.
    If This Then What? Controlling Flows in IoT Apps2018Conference paper (Refereed)
    Abstract [en]

    IoT apps empower users by connecting a variety of otherwise unconnected services. These apps (or applets) are triggered by external information sources to perform actions on external information sinks. We demonstrate that the popular IoT app platforms, including IFTTT (If This Then That), Zapier, and Microsoft Flow are susceptible to attacks by malicious applet makers, including stealthy privacy attacks to exfiltrate private photos, leak user location, and eavesdrop on user input to voice-controlled assistants. We study a dataset of 279,828 IFTTT applets from more than 400 services, classify the applets according to the sensitivity of their sources, and find that 30% of the applets may violate privacy. We propose two countermeasures for short-and longterm protection: access control and information flow control. For short-term protection, we suggest that access control classifies an applet as either exclusively private or exclusively public, thus breaking flows from private sources to sensitive sinks. For longterm protection, we develop a framework for information flow tracking in IoT apps. The framework models applet reactivity and timing behavior, while at the same time faithfully capturing the subtleties of attacker observations caused by applet output. We show how to implement the approach for an IFTTT-inspired setting leveraging state-of-the-art information flow tracking techniques for JavaScript based on the JSFlow tool and evaluate its effectiveness on a collection of applets.

  • 31.
    Baudry, Benoit
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Software and Computer systems, SCS.
    Harrand, Nicolas
    KTH, School of Electrical Engineering and Computer Science (EECS), Software and Computer systems, SCS.
    Schulte, E.
    Timperley, C.
    Tan, S. H.
    Selakovic, M.
    Ugherughe, E.
    A spoonful of DevOps helps the GI go down2018In: Proceedings - International Conference on Software Engineering, IEEE Computer Society , 2018, p. 35-36Conference paper (Refereed)
    Abstract [en]

    DevOps emphasizes a high degree of automation at all phases of the software development lifecyle. Meanwhile, Genetic Improvement (GI) focuses on the automatic improvement of software artifacts. In this paper, we discuss why we believe that DevOps offers an excellent technical context for easing the adoption of GI techniques by software developers. We also discuss A/B testing as a prominent and clear example of GI taking place in the wild today, albeit one with human-supervised fitness and mutation operators.

  • 32.
    Baumann, Christoph
    et al.
    KTH, School of Computer Science and Communication (CSC), Theoretical Computer Science, TCS.
    Schwarz, Oliver
    RISE SICS.
    Dam, Mads
    KTH, School of Computer Science and Communication (CSC), Theoretical Computer Science, TCS.
    Compositional Verification of Security Properties for Embedded Execution Platforms2017In: PROOFS 2017: 6th International Workshop on Security Proofs for Embedded Systems / [ed] Ulrich Kühne and Jean-Luc Danger and Sylvain Guilley, 2017, Vol. 49, p. 1-16Conference paper (Refereed)
    Abstract [en]

    The security of embedded systems can be dramatically improved through the use of formally verified isolation mechanisms such as separation kernels, hypervisors, or microkernels. For trustworthiness, particularly for system level behaviour, the verifications need precise models of the underlying hardware. Such models are hard to attain, highly complex, and proofs of their security properties may not easily apply to similar but different platforms. This may render verification economically infeasible. To address these issues, we propose a compositional top-down approach to embedded system specification and verification, where the system-on-chip is modeled as a network of distributed automata communicating via paired synchronous message passing. Using abstract specifications for each component allows to delay the development of detailed models for cores, devices, etc., while still being able to verify high level security properties like integrity and confidentiality, and soundly refine the result for different instantiations of the abstract components at a later stage. As a case study, we apply this methodology to the verification of information flow security for an industry scale security-oriented hypervisor on the ARMv8-A platform. The hypervisor statically assigns (multiple) cores to each guest system and implements a rudimentary, but usable, inter guest communication discipline. We have completed a pen-and-paper security proof for the hypervisor down to state transition level and report on a partially completed verification of guest mode security in the HOL4 theorem prover.

  • 33. Baumann, Christoph
    et al.
    Schwarz, Oliver
    Dam, Mads
    KTH, School of Electrical Engineering and Computer Science (EECS), Computer Science, Theoretical Computer Science, TCS.
    On the verification of system-level information flow properties for virtualized execution platforms2019In: Journal of Cryptographic Engineering, ISSN 2190-8508, Vol. 9, no 3, p. 243-261Article in journal (Refereed)
    Abstract [en]

    The security of embedded systems can be dramatically improved through the use of formally verified isolation mechanisms such as separation kernels, hypervisors, or microkernels. For trustworthiness, particularly for system-level behavior, the verifications need precise models of the underlying hardware. Such models are hard to attain, highly complex, and proofs of their security properties may not easily apply to similar but different platforms. This may render verification economically infeasible. To address these issues, we propose a compositional top-down approach to embedded system specification and verification, where the system-on-chip is modeled as a network of distributed automata communicating via paired synchronous message passing. Using abstract specifications for each component allows to delay the development of detailed models for cores, devices, etc., while still being able to verify high-level security properties like integrity and confidentiality, and soundly refine the result for different instantiations of the abstract components at a later stage. As a case study, we apply this methodology to the verification of information flow security for an industry-scale security-oriented hypervisor on the ARMv8-A platform and report on the complete verification of guest mode security properties in the HOL4 theorem prover.

  • 34. Bennaceur, A.
    et al.
    Meinke, Karl
    KTH.
    Machine learning for software analysis: Models, methods, and applications2018In: International Dagstuhl Seminar 16172 Machine Learning for Dynamic Software Analysis: Potentials and Limits, 2016, Springer, 2018, Vol. 11026, p. 3-49Conference paper (Refereed)
    Abstract [en]

    Machine Learning (ML) is the discipline that studies methods for automatically inferring models from data. Machine learning has been successfully applied in many areas of software engineering including: behaviour extraction, testing and bug fixing. Many more applications are yet to be defined. Therefore, a better fundamental understanding of ML methods, their assumptions and guarantees can help to identify and adopt appropriate ML technology for new applications. In this chapter, we present an introductory survey of ML applications in software engineering, classified in terms of the models they produce and the learning methods they use. We argue that the optimal choice of an ML method for a particular application should be guided by the type of models one seeks to infer. We describe some important principles of ML, give an overview of some key methods, and present examples of areas of software engineering benefiting from ML. We also discuss the open challenges for reaching the full potential of ML for software engineering and how ML can benefit from software engineering methods.

  • 35.
    Berezovskyi, Andrii
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    El-khoury, Jad
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    Kacimi, Omar
    Loiret, Frédéric
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    Improving lifecycle query in integrated toolchains using linked data and MQTT-based data warehousing2017Conference paper (Refereed)
    Abstract [en]

      The development of increasingly complex IoT systems requires large engineering environments. These environments generally consist of tools from different vendors and are not necessarily integrated well with each other. In order to automate various analyses, queries across resources from multiple tools have to be executed in parallel to the engineering activities. In this paper, we identify the necessary requirements on such a query capability and evaluate different architectures according to these requirements. We propose an improved lifecycle query architecture, which builds upon the existing Tracked Resource Set (TRS) protocol, and complements it with the MQTT messaging protocol in order to allow the data in the warehouse to be kept updated in real-time. As part of the case study focusing on the development of an IoT automated warehouse, this architecture was implemented for a toolchain integrated using RESTful microservices and linked data. 

  • 36.
    Bergenhem, Carl
    et al.
    Qamcom Research and Technology AB.
    Meinke, Karl
    KTH, School of Electrical Engineering and Computer Science (EECS), Theoretical Computer Science, TCS.
    Ström, Fabian
    KTH, School of Electrical Engineering and Computer Science (EECS).
    Quantitative Safety Analysis of a Coordinated Emergency Brake Protocol for Vehicle Platoons2018In: Leveraging Applications of Formal Methods, Verification and Validation. Distributed Systems - 8th International Symposium, ISoLA 2018 / [ed] Tiziana Margaria, Bernhard Steffen, Springer, 2018, Vol. 11246, p. 386-404Conference paper (Refereed)
    Abstract [en]

    In this paper, we present a general methodology to estimate safety related parameter values of cooperative cyber-physical system-of- systems. As a case study, we consider a vehicle platoon model equipped with a novel distributed protocol for coordinated emergency braking. The estimation methodology is based on learning-based testing; which is an approach to automated requirements testing that combines machine learning with model checking.

    Our methodology takes into account vehicle dynamics, control algorithm design, inter-vehicle communication protocols and environmental factors such as message packet loss rates. Empirical measurements from road testing of vehicle-to-vehicle communication in a platoon are modeled and used in our case study. We demonstrate that the minimum global time headway for our platoon model equipped with the CEBP function scales well with respect to platoon size.

  • 37. Bessani, A.
    et al.
    Brandt, J.
    Bux, M.
    Cogo, V.
    Dimitrova, L.
    Dowling, Jim
    KTH, School of Information and Communication Technology (ICT), Software and Computer systems, SCS.
    Gholami, Ali
    KTH.
    Hakimzadeh, Kamal
    KTH, School of Information and Communication Technology (ICT), Software and Computer systems, SCS.
    Hummel, M.
    Ismail, Mahmoud
    KTH, School of Information and Communication Technology (ICT), Software and Computer systems, SCS.
    Laure, Erwin
    KTH, School of Computer Science and Communication (CSC), Centres, Centre for High Performance Computing, PDC. KTH, School of Computer Science and Communication (CSC), High Performance Computing and Visualization (HPCViz).
    Leser, U.
    Litton, J. -E
    Martinez, R.
    Niazi, Salman
    KTH, School of Information and Communication Technology (ICT), Software and Computer systems, SCS.
    Reichel, J.
    Zimmermann, K.
    BiobankCloud: A platform for the secure storage, sharing, and processing of large biomedical data sets2016In: 1st International Workshop on Data Management and Analytics for Medicine and Healthcare, DMAH 2015 and Workshop on Big-Graphs Online Querying, Big-O(Q) 2015 held in conjunction with 41st International Conference on Very Large Data Bases, VLDB 2015, Springer, 2016, p. 89-105Conference paper (Refereed)
    Abstract [en]

    Biobanks store and catalog human biological material that is increasingly being digitized using next-generation sequencing (NGS). There is, however, a computational bottleneck, as existing software systems are not scalable and secure enough to store and process the incoming wave of genomic data from NGS machines. In the BiobankCloud project, we are building a Hadoop-based platform for the secure storage, sharing, and parallel processing of genomic data. We extended Hadoop to include support for multi-tenant studies, reduced storage requirements with erasure coding, and added support for extensible and consistent metadata. On top of Hadoop, we built a scalable scientific workflow engine featuring a proper workflow definition language focusing on simple integration and chaining of existing tools, adaptive scheduling on Apache Yarn, and support for iterative dataflows. Our platform also supports the secure sharing of data across different, distributed Hadoop clusters. The software is easily installed and comes with a user-friendly web interface for running, managing, and accessing data sets behind a secure 2-factor authentication. Initial tests have shown that the engine scales well to dozens of nodes. The entire system is open-source and includes pre-defined workflows for popular tasks in biomedical data analysis, such as variant identification, differential transcriptome analysis using RNA-Seq, and analysis of miRNA-Seq and ChIP-Seq data.

  • 38.
    Blouin, Arnaud
    et al.
    Univ Rennes, INSA Rennes, INRIA, CNRS,IRISA, Rennes, France..
    Lelli, Valeria
    Univ Fed Ceara, Fortaleza, Ceara, Brazil..
    Baudry, Benoit
    KTH.
    Coulon, Fabien
    Univ Toulouse Jean Jaures, Toulouse, France..
    User interface design smell: Automatic detection and refactoring of Blob listeners2018In: Information and Software Technology, ISSN 0950-5849, E-ISSN 1873-6025, Vol. 102, p. 49-64Article in journal (Refereed)
    Abstract [en]

    Context. User Interfaces (UIs) intensively rely on event-driven programming: interactive objects send UI events, which capture users' interactions, to dedicated objects called controllers. Controllers use several UI listeners that handle these events to produce UI commands. Objective. First, we reveal the presence of design smells in the code that describes and controls UIs. Second, we demonstrate that specific code analyses are necessary to analyze and refactor UI code, because of its coupling with the rest of the code. Method. We conducted an empirical study on four large Java software systems. We studied to what extent the number of UI commands that a UI listener can produce has an impact on the change- and fault-proneness of the UI listener code. We developed a static code analysis for detecting UI commands in the code. Results. We identified a new type of design smell, called Blob listener, that characterizes UI listeners that can produce more than two UI commands. We proposed a systematic static code analysis procedure that searches for Blob listener that we implement in InspectorGuidget. We conducted experiments on the four software systems for which we manually identified 53 instances of Blob listener. InspectorGuidget successfully detected 52 Blob listeners out of 53. The results exhibit a precision of 81.25% and a recall of 98.11%. We then developed a semi-automatically and behavior-preserving refactoring process to remove Blob listeners. 49.06% of the 53 Blob listeners were automatically refactored. Patches have been accepted and merged. Discussions with developers of the four software systems assess the relevance of the Blob listener. Conclusion. This work shows that UI code also suffers from design smells that have to be identified and characterized. We argue that studies have to be conducted to find other UI design smells and tools that analyze UI code must be developed.

  • 39.
    Bogdanov, Kirill
    et al.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Network Systems Laboratory (NS Lab).
    Reda, Waleed
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Network Systems Laboratory (NS Lab). Université catholique de Louvain.
    Kostic, Dejan
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS, Network Systems Laboratory (NS Lab).
    Maguire Jr., Gerald Q.
    KTH, School of Information and Communication Technology (ICT), Communication Systems, CoS.
    Canini, Marco
    KAUST.
    Kurma: Fast and Efficient Load Balancing for Geo-Distributed Storage Systems: Evaluation of Convergence and Scalability2018Report (Other academic)
    Abstract [en]

    This report provides an extended evaluation of Kurma, a practical implementation of a geo-distributed load balancer for backend storage systems. In this report we demonstrate the ability of distributed Kurma instances to accurately converge to the same solutions within 1% of the total datacenter’s capacity and the ability of Kurma to scale up to 8 datacenters using a single CPU core at each datacenter.

  • 40.
    Bogdanov, Kirill
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Communication Systems, CoS.
    Reda, Waleed
    KTH, School of Electrical Engineering and Computer Science (EECS), Communication Systems, CoS.
    Maguire Jr., Gerald Q.
    KTH, School of Electrical Engineering and Computer Science (EECS), Communication Systems, CoS.
    Kostic, Dejan
    KTH, School of Electrical Engineering and Computer Science (EECS), Communication Systems, CoS.
    Canini, M.
    Fast and accurate load balancing for geo-distributed storage systems2018In: SoCC 2018 - Proceedings of the 2018 ACM Symposium on Cloud Computing, Association for Computing Machinery (ACM), 2018, p. 386-400Conference paper (Refereed)
    Abstract [en]

    The increasing density of globally distributed datacenters reduces the network latency between neighboring datacenters and allows replicated services deployed across neighboring locations to share workload when necessary, without violating strict Service Level Objectives (SLOs). We present Kurma, a practical implementation of a fast and accurate load balancer for geo-distributed storage systems. At run-time, Kurma integrates network latency and service time distributions to accurately estimate the rate of SLO violations for requests redirected across geo-distributed datacenters. Using these estimates, Kurma solves a decentralized rate-based performance model enabling fast load balancing (in the order of seconds) while taming global SLO violations. We integrate Kurma with Cassandra, a popular storage system. Using real-world traces along with a geo-distributed deployment across Amazon EC2, we demonstrate Kurma’s ability to effectively share load among datacenters while reducing SLO violations by up to a factor of 3 in high load settings or reducing the cost of running the service by up to 17%.

  • 41. Bousse, Erwan
    et al.
    Leroy, Dorian
    Combemale, Benoit
    Wimmer, Manuel
    Baudry, Benoit
    KTH, School of Electrical Engineering and Computer Science (EECS), Software and Computer systems, SCS.
    Omniscient debugging for executable DSLs2018In: Journal of Systems and Software, ISSN 0164-1212, E-ISSN 1873-1228, Vol. 137, p. 261-288Article in journal (Refereed)
    Abstract [en]

    Omniscient debugging is a promising technique that relies on execution traces to enable free traversal of the states reached by a model (or program) during an execution. While a few General-Purpose Languages (GPLs) already have support for omniscient debugging, developing such a complex tool for any executable Domain Specific Language (DSL) remains a challenging and error prone task. A generic solution must: support a wide range of executable DSLs independently of the metaprogramming approaches used for implementing their semantics; be efficient for good responsiveness. Our contribution relies on a generic omniscient debugger supported by efficient generic trace management facilities. To support a wide range of executable DSLs, the debugger provides a common set of debugging facilities, and is based on a pattern to define runtime services independently of metaprogramming approaches. Results show that our debugger can be used with various executable DSLs implemented with different metaprogramming approaches. As compared to a solution that copies the model at each step, it is on average sixtimes more efficient in memory, and at least 2.2 faster when exploring past execution states, while only slowing down the execution 1.6 times on average.

  • 42.
    Broman, David
    KTH, School of Electrical Engineering and Computer Science (EECS), Software and Computer systems, SCS.
    Hybrid Simulation Safety: Limbos and Zero Crossings2018In: Principles of Modeling: Essays Dedicated to Edward A. Lee on the Occasion of His 60th Birthday, Springer, 2018, p. 106-121Chapter in book (Refereed)
    Abstract [en]

    Physical systems can be naturally modeled by combining continuous and discrete models. Such hybrid models may simplify the modeling task of complex system, as well as increase simulation performance. Moreover, modern simulation engines can often efficiently generate simulation traces, but how do we know that the simulation results are correct? If we detect an error, is the error in the model or in the simulation itself? This paper discusses the problem of simulation safety, with the focus on hybrid modeling and simulation. In particular, two key aspects are studied: safe zero-crossing detection and deterministic hybrid event handling. The problems and solutions are discussed and partially implemented in Modelica and Ptolemy II.

  • 43.
    Broman, David
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Software and Computer systems, SCS.
    Siek, J. G.
    United States.
    Gradually typed symbolic expressions2017In: PEPM 2018 - Proceedings of the ACM SIGPLAN Workshop on Partial Evaluation and Program Manipulation, Co-located with POPL 2018, Association for Computing Machinery (ACM), 2017, p. 15-29Conference paper (Refereed)
    Abstract [en]

    Embedding a domain-specific language (DSL) in a general purpose host language is an efficient way to develop a new DSL. Various kinds of languages and paradigms can be used as host languages, including object-oriented, functional, statically typed, and dynamically typed variants, all having their pros and cons. For deep embedding, statically typed languages enable early c