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  • 251.
    Asghar, Adeel
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Pfeiffer, Andreas
    DLR Institute of System Dynamic and Control, Wessling, Tyskland.
    Palanisamy, Arunkumar
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Mengist, Alachew
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Sjölund, Martin
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Pop, Adrian
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Fritzson, Peter
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Automatic Regression Testing of Simulation Models and Concept for Simulation of Connected FMUs in PySimulator2015In: Proceedings of the 11th International Modelica Conference: Versailles, France, September 21-23, 2015 / [ed] Peter Fritzson, Hilding Elmqvist, Linköping, 2015, p. 671-679Conference paper (Refereed)
    Abstract [en]

    The Modelica and FMI tool ecosystem is growing each year with new tools and methods becoming available. The open Modelica standard promises portability but it is important to ensure that a certain model behaves the same in different Modelica tools or in a different version of the same tool. It is also very important (for model evolution) to check that a new version of the same model produces comparable results. Finally, it is desirable to verify that a model exported in FMU form from a Modelica tool gives exactly the same results as the original model. This paper presents a framework for automatic regression testing as part of PySimulator which provides an efficient and concise way of testing if a model or a range of models behaves in the same way in several tools or versions of a tool by checking that the results produced are essentially identical. The FMI standard has been adopted by many tool vendors and is growing in popularity each year. This paper proposes a concept for building and simulating a system made from connected FMUs generated by different tools. The FMUs for Co-Simulation can be connected together using a GUI. The system model built graphically in this way can be saved for later use or simulated directly inside PySimulator. Active development is going on to support simulation of connected FMUs for Model Exchange.

  • 252.
    Ashjaei, Mohammad
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Behnam, Moris
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Almeida, Luis
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems. University of Porto, Porto, Portugal .
    Nolte, Thomas
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    MTU Configuration for Real-Time Switched Ethernet Networks2016In: Journal of systems architecture, ISSN 1383-7621, E-ISSN 1873-6165, Vol. 70, p. 15-25Article in journal (Refereed)
    Abstract [en]

    In this paper, we show that in real-time switched Ethernet networks reducing the Maximum Transmission Unit (MTU) size may cause an increase or decrease in the response time of messages. This contradicting behavior arises an optimization problem for configuring the MTU size. We formulate the optimization problem in the context of the multi-hop HaRTES architecture, which is a hard real-time Ethernet protocol. As part of the solution, we propose a search-based algorithm to achieve optimum solutions. We modify the algorithm by presenting two techniques to reduce the search space. Then, we propose a heuristic algorithm with a pseudo-polynomial time complexity based on the search-based algorithm. We perform several experiments, and we show that the proposed heuristic results in an improvement regarding messages response times, compared with configuring the MTU to the maximum or minimum values. Moreover, we show in small network configurations that the heuristic performs as good as the search-based algorithm in many cases.

  • 253. Ashjaei, Mohammad
    et al.
    Clegg, Kester
    Corneo, Lorenzo
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Hawkins, Richard
    Jaradat, Omar
    Gulisano, Vincenzo Massimiliano
    Nikolakopoulos, Yiannis
    Service Level Agreements for Safe and Configurable Production Environments2018In: 2018 IEEE 23rd International Conference on Emerging Technologies and Factory Automation (ETFA), IEEE, 2018, p. 1252-1255Conference paper (Refereed)
    Abstract [en]

    This paper focuses on Service Level Agreements (SLAs) for industrial applications that aim to port some of the control functionalities to the cloud. In such applications, industrial requirements should be reflected in SLAs. In this paper, we present an approach to integrate safety-related aspects of an industrial application to SLAs. We also present the approach in a use case. This is an initial attempt to enrich SLAs for industrial settings to consider safety aspects, which has not been investigated thoroughly before.

  • 254.
    Ashjaei, Mohammad
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Du, Yong
    Almeida, L.
    University of Porto, Porto, Portugal .
    Behnam, Moris
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Nolte, Thomas
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Dynamic reconfiguration in HaRTES switched ethernet networks2016In: IEEE International Workshop on Factory Communication Systems - Proceedings, WFCS, 2016, article id Article number 7496510Conference paper (Refereed)
    Abstract [en]

    The ability of reconfiguring a system during runtime is essential for dynamic real-time applications in which resource usage is traded online for quality of service. The HaRTES switch, which is a modified Ethernet switch, holds this ability for the network resource, and at the same time it provides hard real-time support for both periodic and sporadic traffic. Although the HaRTES switch technologically caters this ability, a protocol to actually perform the dynamic reconfiguration is missing in multi-hop HaRTES networks. In this paper we introduce such a protocol that is compatible with the traffic scheduling method used in the architecture. We prove the correctness of the protocol using a model checking technique. Moreover, we conduct a set of simulation experiments to show the performance of the protocol and we also show that the reconfiguration process is terminated within a bounded time. 

  • 255.
    Ashjaei, Mohammad
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Khalilzad, Nima
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Mubeen, Saad
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems. IS (Embedded Systems).
    Behnam, Moris
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Sander, Ingo
    Royal Institute of Technology, Sweden.
    Almeida, Luis
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Nolte, Thomas
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    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)
    Abstract [en]

    Contemporary distributed embedded systems in many domains have become highly complex due to ever-increasing demand on advanced computer controlled functionality. The resource reservation techniques can be effective in lowering the software complexity, ensuring predictability and allowing flexibility during the development and execution of these systems. This paper proposes a novel end-to-end resource reservation model for distributed embedded systems. In order to support the development of predictable systems using the proposed model, the paper provides a method to design resource reservations and an end-to-end timing analysis. The reservation design can be subjected to different optimization criteria with respect to runtime footprint, overhead or performance. The paper also presents and evaluates a case study to show the usability of the proposed model, reservation design method and end-to-end timing analysis. 

  • 256. 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)
  • 257.
    Ashjaei, Mohammad
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Mubeen, Saad
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Behnam, Moris
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Almeida, Luis
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Nolte, Thomas
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    End-to-end Resource Reservations in Distributed Embedded Systems2016In: Proceedings - 2016 IEEE 22nd International Conference on Embedded and Real-Time Computing Systems and Applications, RTCSA 2016, 2016, p. 1-11, article id 7579921Conference paper (Refereed)
    Abstract [en]

    The resource reservation techniques provide effective means to lower the software complexity, ensure predictability and allow flexibility during the development and execution of complex distributed embedded systems. In this paper we propose a new end-to-end resource reservation model for distributed embedded systems. The model is comprehensive in such a way that it supports end-to-end resource reservations on distributed transactions with various activation patterns that are commonly used in industrial control systems. The model allows resource reservations on processors and real-time network protocols. We also present timing analysis for the distributed embedded systems that are developed using the proposed model. The timing analysis computes the end-to-end response times as well as delays such as data age and reaction delays. The presented analysis also supports real-time networks that can autonomously initiate transmissions. Such networks are not supported by the existing analyses. We also include a case study to show the usability of the model and end-to-end timing analysis with resource reservations.

  • 258.
    Ashjaei, Mohammad
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Patti, Gaetano
    University of Catania, Italy.
    Behnam, Moris
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Nolte, Thomas
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Alderisi, Giuliana
    University of Catania, Italy.
    Lo Bello, Lucia
    University of Catania, Italy.
    Schedulability Analysis of Ethernet Audio Video Bridging Networks with Scheduled Traffic Support2017In: Real-time systems, ISSN 0922-6443, E-ISSN 1573-1383, Vol. 53, no 4, p. 526-577Article in journal (Refereed)
    Abstract [en]

    The IEEE Audio Video Bridging (AVB) technology is nowadays under consideration in several automation domains, such as, automotive, avionics, and industrial communications. AVB offers several benefits, such as open specifications, the existence of multiple providers of electronic components, and the real-time support, as AVB provides bounded latency to real-time traffic classes. In addition to the above mentioned properties, in the automotive domain, comparing with the existing in-vehicle networks, AVB offers significant advantages in terms of high bandwidth, significant reduction of cabling costs, thickness and weight, while meeting the challenging EMC/EMI requirements. Recently, an improvement of the AVB protocol, called the AVB ST, was proposed in the literature, which allows for supporting scheduled traffic, i.e., a class of time-sensitive traffic that requires time-driven transmission and low latency. In this paper, we present a schedulability analysis for the real-time traffic crossing through the AVB ST network. In addition, we formally prove that, if the bandwidth in the network is allocated according to the AVB standard, the schedulability test based on response time analysis will fail for most cases even if, in reality, these cases are schedulable. In order to provide guarantees based on analysis test a bandwidth over-reservation is required. In this paper, we propose a solution to obtain a minimized bandwidth over-reservation. To the best of our knowledge, this is the first attempt to formally spot the limitation and to propose a solution for overcoming it. The proposed analysis is applied to both the AVB standard and the AVB ST. The analysis results are compared with the results of several simulative assessments, obtained using OMNeT++, on both automotive and industrial case studies. The comparison between the results of the analysis and the simulation ones shows the effectiveness of the analysis proposed in this work.

  • 259.
    Ashjaei, Seyed Mohammad Hossein
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Clegg, Kester
    University of York, UK.
    Corneo, Lorenzo
    Uppsala University, Sweden.
    Hawkins, Richard
    University of York, UK.
    Jaradat, Omar
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Gulisano, Vincenzo
    Chalmers University of Technology, Göteborg, Sweden.
    Nikolakopoulos, Yiannis
    Chalmers University of Technology, Göteborg, Sweden.
    Service Level Agreements for Safe and Configurable Production Environments2018In: International Conference on Emerging Technologies and Factory Automation - Work in Progress Session ETFA-WiP'18, 2018, p. 1252-1255, article id 8502568Conference paper (Refereed)
    Abstract [en]

    This paper focuses on Service Level Agreements (SLAs) for industrial applications that aim to port some of the control functionalities to the cloud. In such applications, industrial requirements should be reflected in SLAs. In this paper, we present an approach to integrate safety-related aspects of an industrial application to SLAs. We also present the approach in a use case. This is an initial attempt to enrich SLAs for industrial settings to consider safety aspects, which has not been investigated thoroughly before.

  • 260.
    Ashjaei, Seyed Mohammad Hossein
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Khalilzad, Nima
    Qamcom Research and Technology, Stockholm, Sweden.
    Mubeen, Saad
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Modeling, Designing and Analyzing Resource Reservations in Distributed Embedded Systems2018In: Real-Time Modelling and Processing for Communication Systems / [ed] Springer, Springer , 2018, p. 203-256Chapter in book (Other academic)
  • 261.
    Ashjaei, Seyed Mohammad Hossein
    et al.
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Mubeen, Saad
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Lundbäck, John
    Arcticus Systems AB, Sweden.
    Gålnander, Mattias
    Arcticus Systems AB, Sweden.
    Lundbäck, Kurt-Lennart
    Arcticus Systems AB, Sweden.
    Nolte, Thomas
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Modeling and Timing Analysis of Vehicle Functions Distributed over Switched Ethernet2017In: IECON 2017 - 43RD ANNUAL CONFERENCE OF THE IEEE INDUSTRIAL ELECTRONICS SOCIETY, 2017, p. 8419-8424Conference paper (Refereed)
    Abstract [en]

    This paper proposes an approach to model switched Ethernet communication within a model- and component-based software development framework for vehicular distributed embedded systems. The paper also presents a method to extract the network timing model from the systems that use switched Ethernet networks. In order to provide a proof of concept, an existing industrial component model and its tool suite, namely RCM and Rubus-ICE respectively, are extended by implementing the modeling technique, the timing model extraction method and response-time analysis of the Ethernet AVB protocol. The extensions to RCM are backward compatible with the modeling and end-to-end timing analysis of traditional in-vehicle networks and legacy (previously developed) vehicular distributed embedded systems. Furthermore, the paper discusses the implementation and test strategy used in this work. Finally, the usability of the modeling approach and implemented timing analysis is demonstrated by modeling and time analyzing a vehicular application case study with the extended component model and tool suite.

  • 262.
    Aslam, Mudassar
    Mälardalen University, School of Innovation, Design and Engineering. Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Bringing Visibility in the Clouds: using Security, Transparency and Assurance Services2014Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The evolution of cloud computing allows the provisioning of IT resources over the Internet and promises many benefits for both - the service users and providers. Despite various benefits offered by cloud based services, many users hesitate in moving their IT systems to the cloud mainly due to many new security problems introduced by cloud environments. In fact, the characteristics of cloud computing become basis of new problems, for example, support of third party hosting introduces loss of user control on the hardware; similarly, on-demand availability requires reliance on complex and possibly insecure API interfaces; seamless scalability relies on the use of sub-providers; global access over public Internet exposes to broader attack surface; and use of shared resources for better resource utilization introduces isolation problems in a multi-tenant environment. These new security issues in addition to existing security challenges (that exist in today's classic IT environments) become major reasons for the lack of user trust in cloud based services categorized in Software-as-a-Service (SaaS), Platform-as-a-Service (PaaS) or Infrastructure-as-a-Service (IaaS).

    The focus of this thesis is on IaaS model which allows users to lease IT resources (e.g. computing power, memory, storage, etc.) from a public cloud to create Virtual Machine (VM) instances. The public cloud deployment model considered in this thesis exhibits most elasticity (i.e. degree of freedom to lease/release IT resources according to user demand) but is least secure as compared to private or hybrid models. As a result, public clouds are not trusted for many use cases which involve processing of security critical data such as health records, financial data, government data, etc. However, public IaaS clouds can also be made trustworthy and viable for these use cases by providing better transparency and security assurance services for the user. In this thesis, we consider such assurance services and identify security aspects which are important for making public clouds trustworthy. Based upon our findings, we propose solutions which promise to improve cloud transparency thereby realizing trustworthy clouds.

    The solutions presented in this thesis mainly deal with the secure life cycle management of the user VM which include protocols and their implementation for secure VM launch and migration. The VM launch and migration solutions ensure that the user VM is always hosted on correct cloud platforms which are setup according to a profile that fulfills the use case relevant security requirements. This is done by using an automated platform security audit and certification mechanism which uses trusted computing and security automation techniques in an integrated solution. In addition to provide the assurance about the cloud platforms, we also propose a solution which provides assurance about the placement of user data in correct and approved geographical locations which is critical from many legal aspects and usually an important requirement of the user. Finally, the assurance solutions provided in this thesis increase cloud transparency which is important for user trust and to realize trustworthy clouds.

  • 263.
    Asplund, Fredrik
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics. KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Embedded Control Systems.
    Exploratory Testing: Do Contextual Factors Influence Software Fault Identification?2018In: Information and Software Technology, ISSN 0950-5849, E-ISSN 1873-6025Article in journal (Refereed)
    Abstract [en]

    Context: Exploratory Testing (ET) is a manual approach to software testing in which learning, test design and test execution occurs simultaneously. Still a developing topic of interest to academia, although as yet insufficiently investigated, most studies focus on the skills and experience of the individual tester. However, contextual factors such as project processes, test scope and organisational boundaries are also likely to affect the approach.

    Objective: This study explores contextual differences between teams of testers at a MedTec firm developing safety-critical products to ascertain whether contextual factors can influence the outcomes of ET, and what associated implications can be drawn for test management.

    Method: A development project was studied in two iterations, each consisting of a quantitative phase testing hypotheses concerning when ET would identify faults in comparison to other testing approaches and a qualitative phase involving interviews.

    Results: Influence on ET is traced to how the scope of tests focus learning on different types of knowledge and imply an asymmetry in the strength and number of information flows to test teams.

    Conclusions: While test specialisation can be attractive to software development organisations, results suggest changes to processes and organisational structures might be required to maintain test efficiency throughout projects: the responsibility for test cases might need to be rotated late in projects, and asymmetries in information flows might require management to actively strengthen the presence and connections of test teams throughout the firm. However, further research is needed to investigate whether these results also hold for non safety-critical faults.

  • 264.
    Asplund, Fredrik
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    Risks Related to the Use of Software Tools when Developing Cyber-Physical Systems: A Critical Perspective on the Future of Developing Complex, Safety-Critical Systems2014Doctoral thesis, monograph (Other academic)
    Abstract [en]

    The increasing complexity and size of modern Cyber-Physical Systems (CPS) has led to a sharp decline in productivity among CPS designers. Requirements on safety aggravate this problem further, both by being difficult to ensure and due to their high importance to the public.

    Tools, or rather efforts to facilitate the automation of development processes, are a central ingredient in many of the proposed innovations to mitigate this problem. Even though the safety-related implications of introducing automation in development processes have not been extensively studied, it is known that automation has already had a large impact on operational systems. If tools are to play a part in mitigating the increase in safety-critical CPS complexity, then their actual impact on CPS development, and thereby the safety of the corresponding end products, must be sufficiently understood.

    An survey of relevant research fields, such as system safety, software engineering and tool integration, is provided to facilitate the discussion on safety-related implications of tool usage. Based on the identification of industrial safety standards as an important source of information and considering that the risks posed by separate tools have been given considerable attention in the transportation domain, several high-profile safety standards in this domain have been surveyed. According to the surveyed standards, automation should primarily be evaluated on its reliable execution of separate process steps independent of human operators. Automation that only supports the actions of operators during CPS development is viewed as relatively inconsequential.

    A conceptual model and a reference model have been created based on the surveyed research fields. The former defines the entities and relationships most relevant to safety-related risks associated with tool usage. The latter describes aspects of tool integration and how these relate to each other. By combining these models, a risk analysis could be performed and properties of tool chains which need to be ensured to mitigate risk identified. Ten such safety-related characteristics of tool chains are described.

    These safety-related characteristics provide a systematic way to narrow down what to look for with regard to tool usage and risk. The hypothesis that a large set of factors related to tool usage may introduce risk could thus be tested through an empirical study, which identified safety-related weaknesses in support environments tied both to high and low levels of automation. The conclusion is that a broader perspective, which includes more factors related to tool usage than those considered by the surveyed standards, will be needed.

    Three possible reasons to disregard such a broad perspective have been refuted, namely requirements on development processes enforced by the domain of CPS itself, certain characteristics of safety-critical CPS and the possibility to place trust in a proven, manual development process. After finding no strong reason to keep a narrow perspective on tool usage, arguments are put forward as to why the future evolution of support environments may actually increase the importance of such a broad perspective.

    Suggestions for how to update the mental models of the surveyed safety standards, and other standards like them, are put forward based on this identified need for a broader perspective.

  • 265.
    Asplund, Fredrik
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    Biehl, Matthias
    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.
    Törngren, Martin
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    Tool Integration Beyond Wasserman2011In: Advanced Information Systems Engineering Workshops / [ed] Camille Salinesi, Oscar Pastor, Berlin: Springer-Verlag , 2011, p. 270-281Conference paper (Refereed)
    Abstract [en]

    The typical development environment today consists of many specialized development tools, which are partially integrated, forming a complex tool landscape with partial integration. Traditional approaches for reasoning about tool integration are insufficient to measure the degree of integration and integration optimality in today’s complex tool landscape. This paper presents a reference model that introduces dependencies between, and metrics for, integration aspects to overcome this problem. This model is used to conceive a method for reasoning about tool integration and identify improvements in an industrial case study. Based on this we are able to conclude that our reference model does not detract value from the principles that it is based on, instead it highlights improvements that were not well visible earlier. We conclude the paper by discussing open issues for our reference model, namely if it is suitable to use during the creation of new systems, if the used integration aspects can be subdivided further to support the analysis of secondary issues related to integration, difficulties related to the state dependency between the data and process aspects within the context of developing embedded systems and the analysis of non-functional requirements to support tool integration.

  • 266.
    Asplund, Katarina
    et al.
    Karlstad University, Division for Information Technology.
    Brunstrom, Anna
    Karlstad University, Division for Information Technology.
    Partially Reliable Multimedia Transport2004Report (Other academic)
  • 267.
    Asplund, Katarina
    et al.
    Karlstad University, Division for Information Technology.
    Brunstrom, Anna
    The trade-off Between Latency and Image Quality: A User PerspectiveManuscript (preprint) (Other (popular science, discussion, etc.))
  • 268.
    Asplund, Katarina
    et al.
    Karlstad University, Division for Information Technology.
    Garcia, Johan
    Brunstrom, Anna
    Schneyer, Sean
    Decreasing Transfer Delay Through Partial ReliabilityManuscript (preprint) (Other (popular science, discussion, etc.))
  • 269.
    Asplund, Lars
    et al.
    Mälardalen University, School of Innovation, Design and Engineering.
    Lundqvist, Kristina
    Mälardalen University, School of Innovation, Design and Engineering.
    Safety Critical Systems Based on Formal Models2000In: ACM SIGAda Letters, ISSN 1094-3641, Vol. XX, no 4, p. 32-39Article in journal (Refereed)
    Abstract [en]

    The Ravenscar profile for high integrity systems using Ada 95 is well defined in all real-time aspects. The complexity of the run-time system has been reduced to allow full utilization of formal methods for applications using the Ravenscar profile. In the Mana project a tool set is being developed including a formal model of a Ravenscar compliant run-time system, a gnat compatible run-time system, and an ASIS based tool to allow for the verification of a system including both COTS and code that is reused.

  • 270.
    Asplund, Lars
    et al.
    Uppsala University, Sweden.
    Lundqvist, Kristina
    Massachusetts Institute of Technology, USA.
    Safety Critical Systems Based on Formal Models2000In: ACM SIGAda Ada Letters - special issue on presentations from SIGAda 2000, Vol. XX, Iss. 4, 2000Conference paper (Other academic)
  • 271.
    Asplund, Lars
    et al.
    Mälardalen University, School of Innovation, Design and Engineering.
    Lundqvist, Kristina
    MIT, Cambridge, MA, United States .
    The Gurkh Project: A Framework for Verification and Execution of Mission Critical Applications2003In: AIAA/IEEE Digital Avionics Systems Conference - Proceedings, vol. 2, 2003, p. 10.B.1/1-10.B.1/9Conference paper (Other academic)
    Abstract [en]

    The paper contributes with three methods that together will make a complete tool-set for verification of mission critical applications. The first method is the transformation of existing Ada or VHDL code into an intermediate form. This form is used for verification by numerous different model checkers. The second method is a predictable runtime kernel that has both a verifiable formal model and is implemented in hardware to achieve full predictability. Finally, a method for transforming the intermediate form of the complete system into a hardware unit, the SafetyChip that performs runtime control of the system. This SafetyChip can catch 'out-of-state' behaviors.

  • 272.
    Asplund, Mikael
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Lövhall, Jakob
    Linköping University, Department of Computer and Information Science. Linköping University, Faculty of Science & Engineering.
    Nadjm-Tehrani, Simin
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    In-store payments using Bitcoin2018In: 2018 9TH IFIP INTERNATIONAL CONFERENCE ON NEW TECHNOLOGIES, MOBILITY AND SECURITY (NTMS), IEEE , 2018Conference paper (Refereed)
    Abstract [en]

    The possibility of in-store payments would further increase the potential usefulness of cryptocurrencies. However, this would require much faster transaction verification than current solutions provide (one hour for Bitcoin) since customers are likely not prepared to wait a very long time for their purchase to be accepted by a store. We propose a solution for enabling instore payments with waiting times in the order of a few seconds, which is still compatible with the current Bitcoin protocol. The idea is based on a payment card in combination with a protocol for ensuring that losing a card does not mean losing the money on it. We analyse the required transaction verification delay and also the potentially added risks that the solution brings compared to current systems.

  • 273.
    Asplund, Mikael
    et al.
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Nadjm-Tehrani, Simin
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, Faculty of Science & Engineering.
    Attitudes and Perceptions of IoT Security in Critical Societal Services2016In: IEEE Access, E-ISSN 2169-3536, Vol. 4, p. 2130-2138Article in journal (Refereed)
    Abstract [en]

    A quiet revolution that impacts several sectors, ranging over transport, home automation, energy, industrial control, and health services is undergoing with addition of new networked devices leading to enhanced services. In this paper, we aim to identify information security requirements that are common over several (vertical) sectors, and in particular, ones that impact critical societal services, namely, the energy, water, and health management systems. We present the results of an interview-based study where actors in these sectors were asked about their perceptions and attitudes on the security of Internet of Things (IoT). We set these perceptions and attitudes in context through a literature review of IoT security, and relate to current challenges in this area. This paper demonstrates that despite an overall optimistic view on IoT in critical societal services, there is a lack of consensus on risks related to IoT security.

  • 274.
    Assabie, Yaregal
    et al.
    Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE), Halmstad Embedded and Intelligent Systems Research (EIS).
    Bigun, Josef
    Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE), Halmstad Embedded and Intelligent Systems Research (EIS).
    Ethiopic Document Image Database for Testing Character Recognition Systems2006Report (Other academic)
    Abstract [en]

    In this paper we describe the acquisition and content of a large database of Ethiopic documents for testing and evaluating character recognition systems. The Ethiopic Document Image Database (EDIDB) contains documents written in Amharic and Geez languages. The database was built from a variety of documents such as printouts, books, newspapers, and magazines. Documents written in various font types, sizes and styles were included in the database. Degraded and poor quality documents were also included in the database to represent the real life situation. A total of 1,204 pages were scanned at a resolution of 300 dpi and saved as grayscale images of JPEG format. We also describe an evaluation protocol for standardizing the comparison of recognition systems and their results. The database is made available to the research community through http://www.hh.se/staff/josef/.

  • 275.
    Aster, Maximilian
    Linnaeus University, Faculty of Technology, Department of Computer Science.
    Repackaging Web Pages2013Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Current trends in the market of Web-enabled devices are moving the focus from desktop web pages to pages optimised for a set of other devices like smartphones or tablets. Within this thesis an approach is introduced, able to adapt and automatically transform web pages and even the web applications logic flow into a new kind of representation, specifically for a certain target group. Therefore a general process is defined to describe the various phases that have to be gone through to transform or repackage a website. It serves as the basis for the solution, which was built as part of this thesis, and incorporates state of the art concepts and methods from various fields of Web Science. The implemented artefacts demonstrate how an appropriate architecture looks like and what additional possibilities open up.

  • 276.
    Atif, Sohaib
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information and Communication systems. Mid sweden University.
    Cooperative diversity and downlink power control using PARPS with application to LTE services (eMBMS and CoMP)2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Mobile devices and their applications are continuing to develop and the more advanced they are, the more they require high data ranges and the more they demand of the available wireless communication networks. At present, LTE (Long Term Evolution) is a good solution as it provides the users of mobile devices with a good throughput and a low latency. In the future, the two most important aspects for end users will be system spectral efficiency and system power controlling. This thesis deals with LTE downlink spectral efficiency and power controlling. The thesis will show how, by using IP multicasting for the LTE downlink, the base station is able to provide the necessary data through a significantly smaller spectrum and, additionally, how cooperative diversity, i.e. the cooperation between several base stations, can improve or even maximise the total network channel capacity, regardless of bandwidth size. A Packet and Resource Plan Scheduling algorithm (PARPS) is used to schedule the transmissions, and the results are calculated in MATLAB. By this means it is possible to analyse the efficiency of the spectrum management, the coverage probability and the power controlling for the different transmitters used for the LTE downlink.The LTE downlink scheme is simulated in Matlab for different numbers of transmitters (2-3). IP multicasting over the LTE downlink manages to transmit the same amount of data using less transmission power (50- 66.6%) with a better system spectral efficiency.

  • 277.
    Atig, Mohamed Faouzi
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Bollig, Benedikt
    CNRS, LSV, Paris, France.;ENS Paris Saclay, Paris, France.
    Habermehl, Peter
    CNRS, IRIF, Paris, France.;Univ Paris Diderot, Paris, France..
    Emptiness of Ordered Multi-Pushdown Automata is 2ETIME-Complete2017In: International Journal of Foundations of Computer Science, ISSN 0129-0541, Vol. 28, no 8, p. 945-975Article in journal (Refereed)
    Abstract [en]

    We consider ordered multi-pushdown automata, a multi-stack extension of pushdown automata that comes with a constraint on stack operations: a pop can only be performed on the first non-empty stack (which implies that we assume a linear ordering on the collection of stacks). We show that the emptiness problem for multi-pushdown automata is 2ETIME-complete. Containment in 2ETIME is shown by translating an automaton into a grammar for which we can check if the generated language is empty. The lower bound is established by simulating the behavior of an alternating Turing machine working in exponential space. We also compare ordered multi-pushdown automata with the model of bounded-phase (visibly) multi-stack pushdown automata, which do not impose an ordering on stacks, but restrict the number of alternations of pop operations on different stacks.

  • 278.
    Atig, Mohamed Faouzi
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Bouajjani, Ahmed
    LIAFA, CNRS and University of Paris Diderot.
    Kumar, K. Narayan
    Chennai Mathematical Institute, Chennai, India.
    Saivasan, Prakash
    Chennai Mathematical Institute, Chennai.
    On Bounded Reachability Analysis of Shared Memory Systems2014In: {IARCS} Annual Conference on Foundations of Software Technology and Theoretical Computer Science, {FSTTCS} 2014, December 15-17, 2014, New Delhi, India, 2014Conference paper (Refereed)
  • 279.
    Atig, Mohamed Faouzi
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Bouajjani, Ahmed
    LIAFA, CNRS and University of Paris Diderot.
    Kumar, K. Narayan
    Chennai Mathematical Institute, Chennai, India.
    Saivasan, Prakash
    TU Braunschweig, Germany.
    Parity Games on Bounded Phase Multi-pushdown Systems2017In: Networked Systems: 5th International Conference, NETYS 2017, Marrakech, Morocco, May 17-19, 2017, Proceedings / [ed] Amr El Abbadi and Benoit Garbinato, Cham, 2017, Vol. 10299, p. 272-287Conference paper (Refereed)
    Abstract [en]

    In this paper we address the problem of solving parity games over the configuration graphs of bounded phase multi-pushdown systems. A non-elementary decision procedure was proposed for this problem by A. Seth. In this paper, we provide a simple and inductive construction to solve this problem. We also prove a non-elementary lower-bound, answering a question posed by A. Seth.

  • 280.
    Atig, Mohamed Faouzi
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Bouajjani, Ahmed
    LIAFA, CNRS and University of Paris Diderot.
    Kumar, K. Narayan
    Chennai Mathematical Institute, Chennai, India.
    Saivasan, Prakash
    TU Braunschweig, Germany.
    Verification of Asynchronous Programs with Nested Locks2017In: 37th IARCS Annual Conference on Foundations of Software Technology and Theoretical Computer Science, FSTTCS 2017, December 11-15, 2017, Kanpur, India / [ed] Satya Lokam and R. Ramanujam, Dagstuhl, Germany, 2017, Vol. 93, p. 11:1-11:14Conference paper (Refereed)
    Abstract [en]

    In this paper, we consider asynchronous programs consisting of multiple recursive threads running in parallel. Each of the threads is equipped with a multi-set. The threads can create tasks and post them onto the multi-sets or read a task from their own. In addition, they can synchronise through a finite set of locks. In this paper, we show that the reachability problem for such class of asynchronous programs is undecidable even under the nested locking policy. We then show that the reachability problem becomes decidable (Exp-space-complete) when the locks are not allowed to be held across tasks. Finally, we show that the problem is NP-complete when in addition to previous restrictions, threads always read tasks from the same state.

  • 281.
    Atig, Mohamed Faouzi
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Bouajjani, Ahmed
    LIAFA, CNRS and University of Paris Diderot.
    Parlato, Gennaro
    University of Southampton.
    Context-Bounded Analysis of TSO Systems2014In: From Programs to Systems: The Systems perspective in Computing / [ed] Bensalem, S; Lakhneck, Y; Legay, A, Springer, 2014, p. 21-38Conference paper (Other academic)
    Abstract [en]

    We address the state reachability problem in concurrent programs running over the TSO weak memory model. This problem has been shown to be decidable with non-primitive recursive complexity in the case of finite-state threads. For recursive threads this problem is undecidable. The aim of this paper is to provide under-approximate analyses for TSO systems that are decidable and have better (elementary) complexity. We propose three bounding concepts for TSO behaviors that are inspired from the concept of bounding the number of context switches introduced by Qadeer and Rehof for the sequentially consistent (SC) model. We investigate the decidability and the complexity of the state reachability problems under these three bounding concepts for TSO, and provide reduction of these problems to known reachability problems of concurrent systems under the SC semantics.

  • 282.
    Atig, Mohamed Faouzi
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Mathematics and Computer Science, Department of Information Technology, Computer Systems.
    Kumar, K. Narayan
    Saivasan, Prakash
    Acceleration in Multi-PushDown Systems2016In: Tools and Algorithms for the Construction and Analysis of Systems, Springer, 2016, p. 698-714Conference paper (Refereed)
  • 283.
    Attarzadeh-Niaki, Seyed Hosein
    et al.
    KTH, School of Information and Communication Technology (ICT), Electronics and Embedded Systems.
    Sander, Ingo
    KTH, School of Information and Communication Technology (ICT), Electronics and Embedded Systems.
    Integrating Functional Mock-up units into a formal heterogeneous system modeling framework2015In: 18th CSI International Symposium on Computer Architecture and Digital Systems, CADS 2015, Institute of Electrical and Electronics Engineers (IEEE), 2015Conference paper (Refereed)
    Abstract [en]

    The Functional Mock-up Interface (FMI) standard defines a method for tool- and platform-independent model exchange and co-simulation of dynamic system models. In FMI, the master algorithm, which executes the imported components, is a timed differential equation solver. This is a limitation for heterogeneous embedded and cyber-physical systems, where models with different time abstractions co-exist and interact. This work integrates FMI into a heterogeneous system modeling and simulation framework as process constructors and co-simulation wrappers. Consequently, each external model communicates with the framework without unnecessary semantic adaptation while the framework provides necessary mechanisms for handling heterogeneity. The presented methods are implemented in the ForSyDe-SystemC modeling framework and tested using a case study.

  • 284.
    Atxutegi, Eneko
    et al.
    Spanien.
    Liberal, Fidel
    Spanien.
    Grinnemo, Karl-Johan
    Karlstad University.
    Brunström, Anna
    Karlstad University.
    Arvidsson, Åke
    Kristianstad University, School of Health and Society, Avdelningen för Design och datavetenskap. Ericsson AB.
    Robert, Rèmi
    Ericsson AB.
    TCP behaviour in LTE: impact of flow start-up and mobility2016In: Wireless and Mobile Networking Conference (WMNC), 2016 9th IFIP, IEEE Communications Society, 2016, p. 73-80Conference paper (Refereed)
    Abstract [en]

    Mobile internet has been widely adopted and it is expected to rise to almost 4 billion users by 2020. Despite the research effort dedicated to the enhancement of its performance, there still exists a gap in the understanding of how TCP and its many variants work over LTE. To this end, this paper evaluates the extent to which five common TCP variants, CUBIC, NewReno,Westwood+, Illinois, and CAIA Delay Gradient (CDG), are able to utilise available radio resources under hard conditions, such as during start-up and in mobile scenarios at different speeds. The paper suggests that CUBIC, due to its Hybrid Slow-Start mechanism, enters congestion avoidance prematurely, and thus experiences a prolonged start-up phase. As a result, it is unable to efficiently utilise radio resources during shorter transmissionsessions. Besides, CUBIC, Illinois and NewReno, i.e., the loss-based TCP implementations, offer better throughput, and are able to better utilise available resources during mobility than Westwood+ and CDG - the delay-based variants do.

  • 285.
    Augustsson, Jesper
    et al.
    Linnaeus University, Faculty of Technology, Department of Informatics.
    Salomonsson, Peter
    Linnaeus University, Faculty of Technology, Department of Informatics.
    Gamification - Samspelet mellan människor och IT: Undersökning av spelmekanismers motivationshöjande effekter2015Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This bachelor thesis is a study to investigate the game mechanics in a selected training application. The study aims to create a greater understanding of why people get motivational effects with the help of information technology. This will be done by examining the users of the example Nike + to find out what features they consider giving them a motivating effect and thus describe the game mechanics these include.

     

    The study uses a qualitative approach to carryout interviews with the users of our example Nike+. The interview questions are based in theory of the field Gamification and previous research on the topic.

     

    The result shows that there are several different game mechanics implemented in Nike +, which has a positive impact on users. The result strengthens the game mechanics informants set positively towards making running a fun form of exercise as well as increased training frequency of our informants.

  • 286.
    Aurelius, Andreas
    et al.
    Acreo.
    Arvidsson, Åke
    Ericsson AB.
    Heegard, Poul
    Norge.
    Villa, Björn
    Norge.
    Kihl, Maria
    Lunds Universitet.
    Zhang, Yichi
    Kungliga Tekniska Högskolan.
    How much of the bandwidth do we actually use?: an investigation of residential access traffic load2012In: ICTON 2012 / [ed] Bozena Jaskorzynska och Richard De La Rue, IEEE Communications Society, 2012Conference paper (Refereed)
    Abstract [en]

    Internet traffic from a fibre based residential access network is investigated concerning traffic volumes and link load. Also the cost of the services is analyzed. We show that 1 Mbps accesses subscribers maintain high loads, and that the price they pay per GB used is five times higher than the one paid by 100 Mbps access subscribers.

  • 287. Avdagic, Zikrija
    et al.
    Boskovic, Dusanka
    Causevic, Aida
    Mälardalen University, School of Innovation, Design and Engineering.
    Code Evaluation Using Fuzzy Logic2008Conference paper (Refereed)
    Abstract [en]

    This paper presents application of a fuzzy logic based system to automatically evaluate the

    maintainability of code. Code evaluation is accomplished by rating its quality provided with bad smells in

    code as inputs. Straightforward bad smells with existing software metrics tools are selected as inputs:

    duplicated code, long methods, large classes having a high cyclomatic complexity, or a large number of

    parameters and temporary fields. Removing these bad smells can result in significant code improvements

    concerning readability and maintainability. However, the precise definition of attributes like small, long, large

    or high is not clear, and their identification is rather subjective. Fuzzy logic values are suitable for capturing

    partial correspondence to attributes and fuzzy rules model have been used to describe the relation between bad

    smells and code quality. Model supporting the experimental evaluation of the fuzzy based code evaluation is

    implemented in Java.

    Key-Words: - Fuzzy Logic, Reasoning Systems, Refactoring, Bad Smells

  • 288.
    Avdic, Kenan
    et al.
    Linköping University, Department of Computer and Information Science. Linköping University, The Institute of Technology.
    Melot, Nicolas
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Kessler, Christoph
    Linköping University, Department of Computer and Information Science, Software and Systems. Linköping University, The Institute of Technology.
    Keller, Jörg
    FernUniversität in Hagen.
    Pipelined parallel sorting on the Intel SCC2011In: Fourth Swedish Workshop on Multi-Core Computing MCC-2011: November 23-25, 2011, Linköping University, Linköping, Sweden / [ed] Christoph Kessler, Linköping: Linköping University , 2011, Vol. S. 96-101, p. 96-101Conference paper (Other academic)
    Abstract [en]

    The Single-Chip Cloud Computer (SCC) is an experimental processor created by Intel Labs. It comprises 48 Intel-IA32 cores linked by an on-chip high performance mesh network, as well as four DDR3 memory controllers to access an off-chip main memory. We investigate the adaptation of sorting onto SCC as an algorithm engineering problem. We argue that a combination of pipelined mergesort and sample sort will fit best to SCC's architecture. We also provide a mapping based on integer linear programming to address load balancing and latency considerations. We describe a prototype implementation of our proposai together with preliminary runtime measurements, that indicate the usefulness of this approach. As mergesort can be considered as a representative of the class of streaming applications, the techniques deveioped here should also apply to the other problems in this class, such as many applications for parallel embedded systems, i.e. MPSoC. 

  • 289.
    Avgouleas, Ioannis
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    IoT Networking Resource Allocation and Cooperation2017Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The Internet of Things (IoT) promises that "anything that can be connected, will be connected". It comprises of Information and Communication Technologies that interconnect billions of physical and visual things with some "basic" intelligence. The emerging IoT services will be able to react with minimal human intervention and further contribute to the big data era that requires real-time, ultrareliable, ubiquitous, scalable, and heterogeneous operation.

    This thesis is the result of our investigations on problems dealing with the evolution of such technologies. First, we explore the potential of using relay i.e., intermediate, nodes that assist users to transmit their packets in a a cellular network. Paper I provides insights into how adapting the cooperation of the relay's receiver and transmitter optimizes the network-wide throughput while the relay's queue stability is guaranteed.

    The next part of the thesis copes with the resource allocation of services on IoT devices equipped with multiple network interfaces. The resources are heterogeneous and can be split among dierent interfaces. Additionally, they are not interchangeable. In paper II, we develop optimization models for this resource allocation problem, prove the complexity of the models, and derive results that give intuition into the problems. Moreover, we propose algorithms that approximate the optimal solution and show under which circumstances this is possible.

    Finally, in paper III, we present a resource allocation problem specically for smart cities services. In comparison to the previous problem denition, resources are of one type but the IoT network device can oer capacities that vary over time. Furthermore, services have a tolerance regarding their preferred scheduling, namely, their allocation over time. We parametrize each service with a pricing function to indicate its tolerance to be served at the beginning of the scheduling window. We prove that the problem is computationally hard and provide numerical results to gain insight into how different pricing weight functions impact the allocations' distribution within the scheduling window.

  • 290.
    Avgouleas, Ioannis
    et al.
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Pappas, Nikolaos
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Yuan, Di
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Angelakis, Vangelis
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, Faculty of Science & Engineering.
    Probabilistic Cooperation of a Full-Duplex Relay in Random Access Networks2017In: IEEE Access, E-ISSN 2169-3536, Vol. 5, p. 7394-7404Article in journal (Refereed)
    Abstract [en]

    In this paper, we analyze the probabilistic cooperation of a full-duplex relay in a multiuser random-access network. The relay is equipped with on/off modes for the receiver and the transmitter independently. These modes are modeled as probabilities by which the receiver and the transmitter are activated. We provide analytical expressions for the performance of the relay queue, such as arrival and service rates, stability conditions, and the average queue size. We optimize the relays operation setup to maximize the network-wide throughput while, simultaneously, we keep the relays queue stable and lower the relays receptions and transmissions. Furthermore, we study the effect of the SINR threshold and the self-interference coefficient on the per-user and network-wide throughput. For low SINR threshold, we show under which circumstances it is beneficial to switch off the relay completely, or switch off the relays receiver only.

  • 291.
    Avritzer, A
    et al.
    Siemens Corporate Research, USA.
    Weyuker, Elaine
    AT and T Labs - Research, USA.
    The Automated Generation of Test Cases using an Extended Domain Based Reliability Model2009In: Proceedings of the 2009 ICSE Workshop on Automation of Software Test, AST 2009, 2009, p. 44-52, article id 5069040Conference paper (Refereed)
  • 292.
    Awada, Imad Alex
    et al.
    University Politehnica of Bucharest, Romania.
    Cramariuc, Oana
    IT Cenetr for Science and Technology, Romania.
    Mocanu, Irina
    University Politehnica of Bucharest.
    Seceleanu, Cristina
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Kunnappilly, Ashalatha
    Mälardalen University, School of Innovation, Design and Engineering, Embedded Systems.
    Florea, Adina Magda
    University Politehnica of Bucharest, Romania.
    An end- user perspective on the CAMI Ambient and Assisted Living Project2018In: INTED2018 Proceedings, 2018Conference paper (Refereed)
    Abstract [en]

    In this paper, we present the outcomes and conclusions obtained by involving seniors from three countries (Denmark, Poland and Romania) in an innovative project funded under the European Ambient Assisted Living (ALL) program. CAMI stands for "Companion with Autonomously Mobile Interface" in "Artificially intelligent ecosystem for self-management and sustainable quality of life in AAL". The CAMI solution enables flexible, scalable and individualised services that support elderly to self-manage their daily life and prolong their involvement in the society (sharing knowledge, continue working, etc). This also allows their informal caregivers (family and friends) to continue working and participating in society while caring for their loved ones. The solution is designed as an innovative architecture that allows for individualized, intelligent self-management which can be tailored to an individual's preferences and needs. A user-centred approach has ranked health monitoring, computer supervised physical exercises and voice based interaction among the top favoured CAMI functionalities. Respondents from three countries (Poland, Romania and Denmark) participated in a multinational survey and a conjoint analysis study.

  • 293.
    Awan, Ahsan Javed
    KTH, School of Information and Communication Technology (ICT), Software and Computer systems, SCS.
    Performance Characterization and Optimization of In-Memory Data Analytics on a Scale-up Server2017Doctoral thesis, monograph (Other academic)
    Abstract [en]

    The sheer increase in the volume of data over the last decade has triggered research in cluster computing frameworks that enable web enterprises to extract big insights from big data. While Apache Spark defines the state of the art in big data analytics platforms for (i) exploiting data-flow and in-memory computing and (ii) for exhibiting superior scale-out performance on the commodity machines, little effort has been devoted to understanding the performance of in-memory data analytics with Spark on modern scale-up servers. This thesis characterizes the performance of in-memory data analytics with Spark on scale-up servers.Through empirical evaluation of representative benchmark workloads on a dual socket server, we have found that in-memory data analytics with Spark exhibit poor multi-core scalability beyond 12 cores due to thread level load imbalance and work-time inflation (the additional CPU time spent by threads in a multi-threaded computation beyond the CPU time required to perform the same work in a sequential computation). We have also found that workloads are bound by the latency of frequent data accesses to the memory. By enlarging input data size, application performance degrades significantly due to the substantial increase in wait time during I/O operations and garbage collection, despite 10% better instruction retirement rate (due to lower L1cache misses and higher core utilization).For data accesses, we have found that simultaneous multi-threading is effective in hiding the data latencies. We have also observed that (i) data locality on NUMA nodes can improve the performance by 10% on average,(ii) disabling next-line L1-D prefetchers can reduce the execution time by upto14%. For garbage collection impact, we match memory behavior with the garbage collector to improve the performance of applications between 1.6xto 3x and recommend using multiple small Spark executors that can provide up to 36% reduction in execution time over single large executor. Based on the characteristics of workloads, the thesis envisions near-memory and near storage hardware acceleration to improve the single-node performance of scale-out frameworks like Apache Spark. Using modeling techniques, it estimates the speed-up of 4x for Apache Spark on scale-up servers augmented with near-data accelerators.

  • 294.
    Awan, Ahsan Javed
    KTH, School of Information and Communication Technology (ICT), Software and Computer systems, SCS. KTH Royal Institute of Technology.
    Performance Characterization of In-Memory Data Analytics on a Scale-up Server2016Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The sheer increase in volume of data over the last decade has triggered research in cluster computing frameworks that enable web enterprises to extract big insights from big data. While Apache Spark defines the state of the art in big data analytics platforms for (i) exploiting data-flow and in-memory computing and (ii) for exhibiting superior scale-out performance on the commodity machines, little effort has been devoted at understanding the performance of in-memory data analytics with Spark on modern scale-up servers. This thesis characterizes the performance of in-memory data analytics with Spark on scale-up servers.

    Through empirical evaluation of representative benchmark workloads on a dual socket server, we have found that in-memory data analytics with Spark exhibit poor multi-core scalability beyond 12 cores due to thread level load imbalance and work-time inflation. We have also found that workloads are bound by the latency of frequent data accesses to DRAM. By enlarging input data size, application performance degrades significantly due to substantial increase in wait time during I/O operations and garbage collection, despite 10% better instruction retirement rate (due to lower L1 cache misses and higher core utilization).

    For data accesses we have found that simultaneous multi-threading is effective in hiding the data latencies. We have also observed that (i) data locality on NUMA nodes can improve the performance by 10% on average, (ii) disabling next-line L1-D prefetchers can reduce the execution time by up-to 14%. For GC impact, we match memory behaviour with the garbage collector to improve performance of applications between 1.6x to 3x. and recommend to use multiple small executors that can provide up-to 36% speedup over single large executor.

  • 295.
    Awan, Ahsan Javed
    et al.
    KTH, School of Information and Communication Technology (ICT), Software and Computer systems, SCS.
    Brorsson, Mats
    KTH, School of Information and Communication Technology (ICT), Software and Computer systems, SCS.
    Vlassov, Vladimir
    KTH, School of Information and Communication Technology (ICT), Software and Computer systems, SCS.
    Ayguade, Eduard
    Barcelona Super Computing Center and Technical University of Catalunya.
    Architectural Impact on Performance of In-memoryData Analytics: Apache Spark Case StudyManuscript (preprint) (Other academic)
    Abstract [en]

    While cluster computing frameworks are contin-uously evolving to provide real-time data analysis capabilities,Apache Spark has managed to be at the forefront of big data an-alytics for being a unified framework for both, batch and streamdata processing. However, recent studies on micro-architecturalcharacterization of in-memory data analytics are limited to onlybatch processing workloads. We compare micro-architectural per-formance of batch processing and stream processing workloadsin Apache Spark using hardware performance counters on a dualsocket server. In our evaluation experiments, we have found thatbatch processing are stream processing workloads have similarmicro-architectural characteristics are bounded by the latency offrequent data access to DRAM. For data accesses we have foundthat simultaneous multi-threading is effective in hiding the datalatencies. We have also observed that (i) data locality on NUMAnodes can improve the performance by 10% on average and(ii)disabling next-line L1-D prefetchers can reduce the executiontime by up-to 14% and (iii) multiple small executors can provideup-to 36% speedup over single large executor

  • 296.
    Awan, Ahsan Javed
    et al.
    KTH, School of Information and Communication Technology (ICT), Software and Computer systems, SCS.
    Brorsson, Mats
    KTH, School of Information and Communication Technology (ICT), Software and Computer systems, SCS.
    Vlassov, Vladimir
    KTH, School of Information and Communication Technology (ICT), Software and Computer systems, SCS.
    Ayguade, Eduard
    Technical University of Catalunya, Barcelona Super Computing Center.
    How Data Volume Affects Spark Based Data Analytics on a Scale-up Server2015In: Big Data Benchmarks, Performance Optimization, and Emerging Hardware: 6th Workshop, BPOE 2015, Kohala, HI, USA, August 31 - September 4, 2015. Revised Selected Papers, Springer, 2015, Vol. 9495, p. 81-92Conference paper (Refereed)
    Abstract [en]

    Sheer increase in volume of data over the last decade has triggered research in cluster computing frameworks that enable web enterprises to extract big insights from big data. While Apache Spark is gaining popularity for exhibiting superior scale-out performance on the commodity machines, the impact of data volume on the performance of Spark based data analytics in scale-up configuration is not well understood. We present a deep-dive analysis of Spark based applications on a large scale-up server machine. Our analysis reveals that Spark based data analytics are DRAM bound and do not benefit by using more than 12 cores for an executor. By enlarging input data size, application performance degrades significantly due to substantial increase in wait time during I/O operations and garbage collection, despite 10 % better instruction retirement rate (due to lower L1 cache misses and higher core utilization). We match memory behaviour with the garbage collector to improve performance of applications between 1.6x to 3x.

  • 297.
    Awan, Ahsan Javed
    et al.
    KTH, School of Information and Communication Technology (ICT), Software and Computer systems, SCS.
    Brorsson, Mats
    KTH, School of Information and Communication Technology (ICT), Software and Computer systems, SCS.
    Vlassov, Vladimir
    KTH, School of Information and Communication Technology (ICT), Software and Computer systems, SCS.
    Ayguade, Eduard
    Barcelona Super Computing Center and Technical University of Catalunya.
    Micro-architectural Characterization of Apache Spark on Batch and Stream Processing Workloads2016Conference paper (Refereed)
    Abstract [en]

    While cluster computing frameworks are continuously evolving to provide real-time data analysis capabilities, Apache Spark has managed to be at the forefront of big data analytics for being a unified framework for both, batch and stream data processing. However, recent studies on micro-architectural characterization of in-memory data analytics are limited to only batch processing workloads. We compare the micro-architectural performance of batch processing and stream processing workloads in Apache Spark using hardware performance counters on a dual socket server. In our evaluation experiments, we have found that batch processing and stream processing has same micro-architectural behavior in Spark if the difference between two implementations is of micro-batching only. If the input data rates are small, stream processing workloads are front-end bound. However, the front end bound stalls are reduced at larger input data rates and instruction retirement is improved. Moreover, Spark workloads using DataFrames have improved instruction retirement over workloads using RDDs.

  • 298.
    Awan, Ahsan Javed
    et al.
    KTH, School of Information and Communication Technology (ICT), Software and Computer systems, SCS.
    Brorsson, Mats
    KTH, School of Information and Communication Technology (ICT), Software and Computer systems, SCS.
    Vlassov, Vladimir
    KTH, School of Information and Communication Technology (ICT), Software and Computer systems, SCS.
    Ayguade, Eduard
    Barcelona Super Computing Center and Technical University of Catalunya.
    Node architecture implications for in-memory data analytics on scale-in clusters2016Conference paper (Refereed)
    Abstract [en]

    While cluster computing frameworks are continuously evolving to provide real-time data analysis capabilities, Apache Spark has managed to be at the forefront of big data analytics. Recent studies propose scale-in clusters with in-storage processing devices to process big data analytics with Spark However the proposal is based solely on the memory bandwidth characterization of in-memory data analytics and also does not shed light on the specification of host CPU and memory. Through empirical evaluation of in-memory data analytics with Apache Spark on an Ivy Bridge dual socket server, we have found that (i) simultaneous multi-threading is effective up to 6 cores (ii) data locality on NUMA nodes can improve the performance by 10% on average, (iii) disabling next-line L1-D prefetchers can reduce the execution time by up to 14%, (iv) DDR3 operating at 1333 MT/s is sufficient and (v) multiple small executors can provide up to 36% speedup over single large executor.

  • 299.
    Axelsson, Andreas
    et al.
    Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE).
    Ambrosius, Christian
    Halmstad University, School of Information Science, Computer and Electrical Engineering (IDE).
    Nya lagar och avtal: Hur kan de komma att förändra svenskarnas fildelningsvanor?2012Independent thesis Basic level (university diploma), 5 credits / 7,5 HE creditsStudent thesis
    Abstract [sv]

    I många år nu har det varit vanligt förekommande att människor suttit hemma vid sin dator och med några få klick laddat ner filmer, musik och programvaror, till en början helt lagligt, men med åren har lagar kommit till som har gjort det mer och mer olagligt.Oavsett om det har varit lagligt eller inte, så är det troligt att många artister, filmmakare och liknande gått miste om stora summor pengar i förlorade inkomster på grund av att folk inte har betalat för att ta del av deras verk, utan istället valt att ladda ner dem över Internet.

    Det faktum att fildelning har blivit så pass vanligt och att folk inte har sett det som ett särskilt allvarligt brott, har lett till att fildelning länge har varit ett hett omdiskuterat ämne i media, bland upphovsrättsinnehavare och bland folk i allmänhet. Upphovsmän och upphovsrättsinnehavare, såsom filmbolag, författare och artister har legat på och debatterat för att försöka få till en hårdare lagstiftning för att försvåra fildelning och kopiering av upphovsrättsskyddat material, samt för att få till hårdare straff mot fildelning.

    Flera försök från beslutsfattare har gjorts för att råda bot på problemet, nya lagar har stiftats och avtal har skrivits under. Frågan är om de nya lagarna och avtalen gör någon nytta? Blir folk avskräckta från att fildela eller fortsätter de som förut? Många har säkert under många år blivit bortskämda med att kunna sitta hemma vid datorn och på några minuter få hem de senaste filmerna och den nyaste musiken helt gratis, vilket säkert gör det svårt att helt plötsligt sluta fildela och börja betala för film och musik igen.

  • 300.
    Axelsson, Jakob
    Software and Systems Engineering Laboratory, Swedish Institute of Computer Science (SICS), Kista, Sweden .
    A Systematic Mapping of the Research Literature on System-of-Systems Engineering2015In: 10th Annual Systems of Systems Engineering Conference SOSE, 2015, p. 18-23Conference paper (Refereed)
    Abstract [en]

    The research area systems-of-systems engineering has increased rapidly over the last decade and now contains a substantial body of literature. To get an overview of the field, a systematic mapping of the literature has been done, covering over 3000 papers. It revealed a field massively dominated by US researchers, with an emphasis on military and space systems. A large number of people are involved, but few researchers focus on the area, and citations are fairly low compared to other fields. Important research topics include architecture, modeling and simulation, integration and interoperability, communication, sustainability, and safety and security. There are signs of immaturity within the research area, and it is recommended that existing venues are complemented with an international scientific event with very high standards for submissions.

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