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  • 1. Abel, Olubunmi
    et al.
    Shatunov, Aleksey
    Jones, Ashley R.
    Andersen, Peter M.
    Umeå University, Faculty of Medicine, Department of Pharmacology and Clinical Neuroscience, Neurology.
    Powell, John F.
    Al-Chalabi, Ammar
    Development of a Smartphone App for a Genetics Website: The Amyotrophic Lateral Sclerosis Online Genetics Database (ALSoD)2013In: JMIR mhealth and uhealth, E-ISSN 2291-5222, Vol. 1, no 2, article id e18Article in journal (Refereed)
    Abstract [en]

    Background: The ALS Online Genetics Database (ALSoD) website holds mutation, geographical, and phenotype data on genes implicated in amyotrophic lateral sclerosis (ALS) and links to bioinformatics resources, publications, and tools for analysis. On average, there are 300 unique visits per day, suggesting a high demand from the research community. To enable wider access, we developed a mobile-friendly version of the website and a smartphone app. Objective: We sought to compare data traffic before and after implementation of a mobile version of the website to assess utility. Methods: We identified the most frequently viewed pages using Google Analytics and our in-house analytic monitoring. For these, we optimized the content layout of the screen, reduced image sizes, and summarized available information. We used the Microsoft. NET framework mobile detection property (HttpRequest. IsMobileDevice in the Request. Browser object in conjunction with HttpRequest. UserAgent), which returns a true value if the browser is a recognized mobile device. For app development, we used the Eclipse integrated development environment with Android plug-ins. We wrapped the mobile website version with the WebView object in Android. Simulators were downloaded to test and debug the applications. Results: The website automatically detects access from a mobile phone and redirects pages to fit the smaller screen. Because the amount of data stored on ALSoD is very large, the available information for display using smartphone access is deliberately restricted to improve usability. Visits to the website increased from 2231 to 2820, yielding a 26% increase from the pre-mobile to post-mobile period and an increase from 103 to 340 visits (230%) using mobile devices (including tablets). The smartphone app is currently available on BlackBerry and Android devices and will be available shortly on iOS as well. Conclusions: Further development of the ALSoD website has allowed access through smartphones and tablets, either through the website or directly through a mobile app, making genetic data stored on the database readily accessible to researchers and patients across multiple devices.

  • 2.
    Ali-Eldin, Ahmed
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Capacity Scaling for Elastic Compute Clouds2013Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    AbstractCloud computing is a computing model that allows better management, higher utiliza-tion and reduced operating costs for datacenters while providing on demand resourceprovisioning for different customers. Data centers are often enormous in size andcomplexity. In order to fully realize the cloud computing model, efficient cloud man-agement software systems that can deal with the datacenter size and complexity needto be designed and built.This thesis studies automated cloud elasticity management, one of the main andcrucial datacenter management capabilities. Elasticity can be defined as the abilityof cloud infrastructures to rapidly change the amount of resources allocated to anapplication in the cloud according to its demand. This work introduces algorithms,techniques and tools that a cloud provider can use to automate dynamic resource pro-visioning allowing the provider to better manage the datacenter resources. We designtwo automated elasticity algorithms for cloud infrastructures that predict the futureload for an application running on the cloud. It is assumed that a request is either ser-viced or dropped after one time unit, that all requests are homogeneous and that it takesone time unit to add or remove resources. We discuss the different design approachesfor elasticity controllers and evaluate our algorithms using real workload traces. Wecompare the performance of our algorithms with a state-of-the-art controller. We ex-tend on the design of the best performing controller out of our two controllers anddrop the assumptions made during the first design. The controller is evaluated with aset of different real workloads.All controllers are designed using certain assumptions on the underlying systemmodel and operating conditions. This limits a controller’s performance if the modelor operating conditions change. With this as a starting point, we design a workloadanalysis and classification tool that assigns a workload to its most suitable elasticitycontroller out of a set of implemented controllers. The tool has two main components,an analyzer and a classifier. The analyzer analyzes a workload and feeds the analysisresults to the classifier. The classifier assigns a workload to the most suitable elasticitycontroller based on the workload characteristics and a set of predefined business levelobjectives. The tool is evaluated with a set of collected real workloads and a set ofgenerated synthetic workloads. Our evaluation results shows that the tool can help acloud provider to improve the QoS provided to the customers.

  • 3.
    Ali-Eldin, Ahmed
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    El-Ansary, Sameh
    Nile University.
    Optimizing Replica Placement in Peer-Assisted Cloud Stores2011Conference paper (Refereed)
    Abstract [en]

    Peer-assisted cloud storage systems use the unutilizedresources of the clients subscribed to a storage cloudto offload the servers of the cloud. The provider distributesdata replicas on the clients instead of replicating on the localinfrastructure. These replicas allow the provider to providea highly available, reliable and cheap service at a reducedcost. In this work we introduce NileStore, a protocol forreplication management in peer-assisted cloud storage. Theprotocol converts the replica placement problem into a lineartask assignment problem. We design five utility functionsto optimize placement taking into account the bandwidth,free storage and the size of data in need of replication oneach peer. The problem is solved using a suboptimal greedyoptimization algorithm. We show our simulation results usingthe different utilities under realistic network conditions. Ourresults show that using our approach offloads the cloud serversby about 90% compared to a random placement algorithmwhile consuming 98.5% less resources compared to a normalstorage cloud.

  • 4.
    Ali-Eldin, Ahmed
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    El-Ansary, Sameh
    Nile University.
    Replica Placement in Peer-Assisted Clouds: An Economic Approach2011In: Lecture Notes in Computer Science / [ed] Pascal Felber, Romain Rouvoy, Springer, 2011, p. 208-213Conference paper (Refereed)
    Abstract [en]

    We introduce NileStore, a replica placement algorithm based on an economical model for use in Peer-assisted cloud storage. The algorithm uses storage and bandwidth resources of peers to offload the cloud provider’s resources. We formulate the placement problem as a linear task assignment problem where the aim is to minimize time needed for file replicas to reach a certain desired threshold. Using simulation, We reduce the probability of a file being served from the provider’s servers by more than 97.5% under realistic network conditions.

  • 5.
    Ali-Eldin, Ahmed
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Ilyushkin, Alexey
    Ghit, Bogdan
    Herbst, Nikolas Roman
    Papadopoulos, Alessandro
    Losup, Alexandru
    Which Cloud Auto-Scaler Should I Use for my Application?: Benchmarking Auto-Scaling Algorithms2016In: PROCEEDINGS OF THE 2016 ACM/SPEC INTERNATIONAL CONFERENCE ON PERFORMANCE ENGINEERING (ICPE'16), Association for Computing Machinery (ACM), 2016, p. 131-132Conference paper (Refereed)
  • 6.
    Ali-Eldin, Ahmed
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Kihl, Maria
    Lund University.
    Tordsson, Johan
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Elmroth, Erik
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Analysis and characterization of a Video-on-Demand service workload2015In: Proceedings of the 6th ACM Multimedia Systems Conference, MMSys 2015, ACM Digital Library, 2015, p. 189-200Conference paper (Refereed)
    Abstract [en]

    Video-on-Demand (VoD) and video sharing services accountfor a large percentage of the total downstream Internet traf-fic. In order to provide a better understanding of the loadon these services, we analyze and model a workload tracefrom a VoD service provided by a major Swedish TV broad-caster. The trace contains over half a million requests gener-ated by more than 20000 unique users. Among other things,we study the request arrival rate, the inter-arrival time, thespikes in the workload, the video popularity distribution, thestreaming bit-rate distribution and the video duration distri-bution. Our results show that the user and the session ar-rival rates for the TV4 workload does not follow a Poissonprocess. The arrival rate distribution is modeled using a log-normal distribution while the inter-arrival time distributionis modeled using a stretched exponential distribution. Weobserve the “impatient user” behavior where users abandonstreaming sessions after minutes or even seconds of startingthem. Both very popular videos and non-popular videos areparticularly affected by impatient users. We investigate ifthis behavior is an invariant for VoD workloads.

  • 7.
    Ali-Eldin, Ahmed
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Rezaie, Ali
    Umeå University, Faculty of Science and Technology, Department of Mathematics and Mathematical Statistics.
    Mehta, Amardeep
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Razroev, Stanislav
    Umeå University, Faculty of Science and Technology, Department of Mathematics and Mathematical Statistics.
    Sjöstedt-de Luna, Sara
    Umeå University, Faculty of Science and Technology, Department of Mathematics and Mathematical Statistics.
    Seleznjev, Oleg
    Umeå University, Faculty of Science and Technology, Department of Mathematics and Mathematical Statistics.
    Tordsson, Johan
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Elmroth, Erik
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    How will your workload look like in 6 years?: Analyzing Wikimedia's workload2014In: Proceedings of the 2014 IEEE International Conference on Cloud Engineering (IC2E 2014) / [ed] Lisa O’Conner, IEEE Computer Society, 2014, p. 349-354Conference paper (Refereed)
    Abstract [en]

    Accurate understanding of workloads is key to efficient cloud resource management as well as to the design of large-scale applications. We analyze and model the workload of Wikipedia, one of the world's largest web sites. With descriptive statistics, time-series analysis, and polynomial splines, we study the trend and seasonality of the workload, its evolution over the years, and also investigate patterns in page popularity. Our results indicate that the workload is highly predictable with a strong seasonality. Our short term prediction algorithm is able to predict the workload with a Mean Absolute Percentage Error of around 2%.

  • 8.
    Ali-Eldin, Ahmed
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Seleznjev, Oleg
    Umeå University, Faculty of Science and Technology, Department of Mathematics and Mathematical Statistics.
    Sjöstedt-de Luna, Sara
    Umeå University, Faculty of Science and Technology, Department of Mathematics and Mathematical Statistics.
    Tordsson, Johan
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Elmroth, Erik
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Measuring cloud workload burstiness2014In: 2014 IEEE/ACM 7th International Conference on Utility and Cloud Computing (UCC), IEEE conference proceedings, 2014, p. 566-572Conference paper (Refereed)
    Abstract [en]

    Workload burstiness and spikes are among the main reasons for service disruptions and decrease in the Quality-of-Service (QoS) of online services. They are hurdles that complicate autonomic resource management of datacenters. In this paper, we review the state-of-the-art in online identification of workload spikes and quantifying burstiness. The applicability of some of the proposed techniques is examined for Cloud systems where various workloads are co-hosted on the same platform. We discuss Sample Entropy (SampEn), a measure used in biomedical signal analysis, as a potential measure for burstiness. A modification to the original measure is introduced to make it more suitable for Cloud workloads.

  • 9.
    Ali-Eldin, Ahmed
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Tordsson, Johan
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Elmroth, Erik
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Kihl, Maria
    Lund University.
    WAC: A Workload analysis and classification tool for automatic selection of cloud auto-scaling methodsManuscript (preprint) (Other academic)
    Abstract [en]

    Autoscaling algorithms for elastic cloud infrastructures dynami-cally change the amount of resources allocated to a service ac-cording to the current and predicted future load. Since there areno perfect predictors, no single elasticity algorithm is suitable foraccurate predictions of all workloads. To improve the quality ofworkload predictions and increase the Quality-of-Service (QoS)guarantees of a cloud service, multiple autoscalers suitable for dif-ferent workload classes need to be used. In this work, we intro-duce WAC, a Workload Analysis and Classification tool that as-signs workloads to the most suitable elasticity autoscaler out of aset of pre-deployed autoscalers. The workload assignment is basedon the workload characteristics and a set of user-defined Business-Level-Objectives (BLO). We describe the tool design and its maincomponents. We implement WAC and evaluate its precision us-ing various workloads, BLO combinations and state-of-the-art au-toscalers. Our experiments show that, when the classifier is tunedcarefully, WAC assigns between 87% and 98.3% of the workloadsto the most suitable elasticity autoscaler.

  • 10.
    Ali-Eldin, Ahmed
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Tordsson, Johan
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Elmroth, Erik
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Kihl, Maria
    Department of Electrical and Information Technology, Lund University, Lund, Sweden.
    Workload Classification for Efficient Auto-Scaling of Cloud Resources2013Manuscript (preprint) (Other academic)
    Abstract [en]

    Elasticity algorithms for cloud infrastructures dynamically change the amount of resources allocated to a running service according to the current and predicted future load. Since there is no perfect predictor, and since different applications’ workloads have different characteristics, no single elasticity algorithm is suitable for future predictions for all workloads. In this work, we introduceWAC, aWorkload Analysis and Classification tool that analyzes workloads and assigns them to the most suitable elasticity controllers based on the workloads’ characteristics and a set of business level objectives.

    WAC has two main components, the analyzer and the classifier. The analyzer analyzes workloads to extract some of the features used by the classifier, namely, workloads’ autocorrelations and sample entropies which measure the periodicity and the burstiness of the workloads respectively. These two features are used with the business level objectives by the clas-sifier as the features used to assign workloads to elasticity controllers. We start by analyzing 14 real workloads available from different applications. In addition, a set of 55 workloads is generated to test WAC on more workload configurations. We implement four state of the art elasticity algorithms. The controllers are the classes to which the classifier assigns workloads. We use a K nearest neighbors classifier and experiment with different workload combinations as training and test sets. Our experi-ments show that, when the classifier is tuned carefully, WAC correctly classifies between 92% and 98.3% of the workloads to the most suitable elasticity controller.

  • 11.
    Ali-Eldin Hassan, Ahmed
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Workload characterization, controller design and performance evaluation for cloud capacity autoscaling2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis studies cloud capacity auto-scaling, or how to provision and release re-sources to a service running in the cloud based on its actual demand using an auto-matic controller. As the performance of server systems depends on the system design,the system implementation, and the workloads the system is subjected to, we focuson these aspects with respect to designing auto-scaling algorithms. Towards this goal,we design and implement two auto-scaling algorithms for cloud infrastructures. Thealgorithms predict the future load for an application running in the cloud. We discussthe different approaches to designing an auto-scaler combining reactive and proactivecontrol methods, and to be able to handle long running requests, e.g., tasks runningfor longer than the actuation interval, in a cloud. We compare the performance ofour algorithms with state-of-the-art auto-scalers and evaluate the controllers’ perfor-mance with a set of workloads. As any controller is designed with an assumptionon the operating conditions and system dynamics, the performance of an auto-scalervaries with different workloads.In order to better understand the workload dynamics and evolution, we analyze a6-years long workload trace of the sixth most popular Internet website. In addition,we analyze a workload from one of the largest Video-on-Demand streaming servicesin Sweden. We discuss the popularity of objects served by the two services, the spikesin the two workloads, and the invariants in the workloads. We also introduce, a mea-sure for the disorder in a workload, i.e., the amount of burstiness. The measure isbased on Sample Entropy, an empirical statistic used in biomedical signal processingto characterize biomedical signals. The introduced measure can be used to charac-terize the workloads based on their burstiness profiles. We compare our introducedmeasure with the literature on quantifying burstiness in a server workload, and showthe advantages of our introduced measure.To better understand the tradeoffs between using different auto-scalers with differ-ent workloads, we design a framework to compare auto-scalers and give probabilisticguarantees on the performance in worst-case scenarios. Using different evaluation cri-teria and more than 700 workload traces, we compare six state-of-the-art auto-scalersthat we believe represent the development of the field in the past 8 years. Knowingthat the auto-scalers’ performance depends on the workloads, we design a workloadanalysis and classification tool that assigns a workload to its most suitable elasticitycontroller out of a set of implemented controllers. The tool has two main components;an analyzer, and a classifier. The analyzer analyzes a workload and feeds the analysisresults to the classifier. The classifier assigns a workload to the most suitable elasticitycontroller based on the workload characteristics and a set of predefined business levelobjectives. The tool is evaluated with a set of collected real workloads, and a set ofgenerated synthetic workloads. Our evaluation results shows that the tool can help acloud provider to improve the QoS provided to the customers.

  • 12.
    Baskar, Jayalakshmi
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Lindgren, Helena
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Human-Agent Dialogues on Health Topics - An Evaluation Study2015In: Highlights of practical applications of agents, multi-agent systems, and sustainability: The PAAMS Collection, PAAMS 2015, 2015, p. 28-39Conference paper (Refereed)
    Abstract [en]

    A common conversation between an older adult and a nurse about health-related issues includes topics such as troubles with sleep, reasons for walking around nighttime, pain conditions, etc. This dialogue emerges from the participating human's lines of thinking, their roles, needs and motives, while switching between topics as the dialogue unfolds. This paper presents a dialogue system that enables a human to engage in a dialogue with a software agent to reason about health-related issues in a home environment. The purpose of this work is to conduct a pilot evaluation study of a prototype system for human-agent dialogues, which is built upon a set of semantic models and integrated in a web application designed for older adults. Focus of the study was to receive qualitative results regarding purpose and content of the agent-based dialogue system, and to evaluate a method for the agent to evaluate its behavior based on the human agent's perception of appropriateness of moves. The participants include five therapists and 11 older adults. The results show users' feedback on the purpose of dialogues and the appropriateness of dialogues presented to them during the interaction with the software agent.

  • 13. Bauer,, André
    et al.
    Herbst, Nikolas
    Spinner, Simon
    Ali-Eldin, Ahmed
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Kounev, Samuel
    Chameleon: A Hybrid, Proactive Auto-Scaling Mechanism on a Level-Playing Field2018In: IEEE Transactions on Parallel and Distributed Systems, ISSN 1045-9219, E-ISSN 1558-2183Article in journal (Refereed)
    Abstract [en]

    Auto-scalers for clouds promise stable service quality at low costs when facing changing workload intensity. The major public cloud providers provide trigger-based auto-scalers based on thresholds. However, trigger-based auto-scaling has reaction times in the order of minutes. Novel auto-scalers from literature try to overcome the limitations of reactive mechanisms by employing proactive prediction methods. However, the adoption of proactive auto-scalers in production is still very low due to the high risk of relying on a single proactive method.

  • 14. Bauer, André
    et al.
    Herbst, Nikolas
    Spinner, Simon
    Ali-Eldin, Ahmed
    Umeå University, Faculty of Science and Technology, Department of Computing Science. UMass, Amherst, MA, USA.
    Kounev, Samuel
    Chameleon: A Hybrid, Proactive Auto-Scaling Mechanism on a Level-Playing Field2019In: IEEE Transactions on Parallel and Distributed Systems, ISSN 1045-9219, E-ISSN 1558-2183, Vol. 30, no 4, p. 800-813Article in journal (Refereed)
    Abstract [en]

    Auto-scalers for clouds promise stable service quality at low costs when facing changing workload intensity. The major public cloud providers provide trigger-based auto-scalers based on thresholds. However, trigger-based auto-scaling has reaction times in the order of minutes. Novel auto-scalers from literature try to overcome the limitations of reactive mechanisms by employing proactive prediction methods. However, the adoption of proactive auto-scalers in production is still very low due to the high risk of relying on a single proactive method. This paper tackles the challenge of reducing this risk by proposing a new hybrid auto-scaling mechanism, called Chameleon, combining multiple different proactive methods coupled with a reactive fallback mechanism. Chameleon employs on-demand, automated time series-based forecasting methods to predict the arriving load intensity in combination with run-time service demand estimation to calculate the required resource consumption per work unit without the need for application instrumentation. We benchmark Chameleon against five different state-of-the-art proactive and reactive auto-scalers one in three different private and public cloud environments. We generate five different representative workloads each taken from different real-world system traces. Overall, Chameleon achieves the best scaling behavior based on user and elasticity performance metrics, analyzing the results from 400 hours aggregated experiment time.

  • 15.
    Bayuh Lakew, Ewnetu
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Birke, Robert
    Perez, Juan F.
    Elmroth, Erik
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Chen, Lydia Y.
    SmallTail: Scaling Cores and Probabilistic Cloning Requests for Web Systems2018In: 15TH IEEE INTERNATIONAL CONFERENCE ON AUTONOMIC COMPUTING (ICAC 2018), IEEE , 2018, p. 31-40Conference paper (Refereed)
    Abstract [en]

    Users quality of experience on web systems are largely determined by the tail latency, e.g., 95th percentile. Scaling resources along, e.g., the number of virtual cores per VM, is shown to be effective to meet the average latency but falls short in taming the latency tail in the cloud where the performance variability is higher. The prior art shows the prominence of increasing the request redundancy to curtail the latency either in the off-line setting or without scaling-in cores of virtual machines. In this paper, we propose an opportunistic scaler, termed SmallTail, which aims to achieve stringent targets of tail latency while provisioning a minimum amount of resources and keeping them well utilized. Against dynamic workloads, SmallTail simultaneously adjusts the core provisioning per VM and probabilistically replicates requests so as to achieve the tail latency target. The core of SmallTail is a two level controller, where the outer loops controls the core provision per distributed VMs and the inner loop controls the clones in a finer granularity. We also provide theoretical analysis on the steady-state latency for a given probabilistic replication that clones one out of N arriving requests. We extensively evaluate SmallTail on three different web systems, namely web commerce, web searching, and web bulletin board. Our testbed results show that SmallTail can ensure the 95th latency below 1000 ms using up to 53% less cores compared to the strategy of constant cloning, whereas scaling-core only solution exceeds the latency target by up to 70%.

  • 16.
    Bensch, Suna
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Björklund, Johanna
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Kutrib, Martin
    Institut fur Informatik, Universität Giessen.
    Deterministic Stack Transducers2016In: Implementation and Application of Automata / [ed] Yo-Sub Han and Kai Salomaa, Springer, 2016, p. 27-38Conference paper (Refereed)
    Abstract [en]

    We introduce and investigate stack transducers, which are one-way stack automata with an output tape. A one-way stack automaton is a classical pushdown automaton with the additional ability to move the stack head inside the stack without altering the contents. For stack transducers, we distinguish between a digging and a non-digging mode. In digging mode, the stack transducer can write on the output tape when its stack head is inside the stack, whereas in non-digging mode, the stack transducer is only allowed to emit symbols when its stack head is at the top of the stack. These stack transducers have a motivation from natural language interface applications, as they capture long-distance dependencies in syntactic, semantic, and discourse structures.We study the computational capacity for deterministic digging and non-digging stack transducers, as well as for their non-erasing and checking versions. We finally show that even for the strongest variant of stack transducers the stack languages are regular.

  • 17.
    Bensch, Suna
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Björklund, Johanna
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Kutrib, Martin
    Deterministic Stack Transducers2017In: International Journal of Foundations of Computer Science, ISSN 0129-0541, Vol. 28, no 5, p. 583-601Article in journal (Refereed)
    Abstract [en]

    We introduce and investigate stack transducers, which are one-way stack automata with an output tape. A one-way stack automaton is a classical pushdown automaton with the additional ability to move the stack head inside the stack without altering the contents. For stack transducers, we distinguish between a digging and a non-digging mode. In digging mode, the stack transducer can write on the output tape when its stack head is inside the stack, whereas in non-digging mode, the stack transducer is only allowed to emit symbols when its stack head is at the top of the stack. These stack transducers have a motivation from natural-language interface applications, as they capture long-distance dependencies in syntactic, semantic, and discourse structures. We study the computational capacity for deterministic digging and non-digging stack transducers, as well as for their non-erasing and checking versions. We finally show that even for the strongest variant of stack transducers the stack languages are regular.

  • 18.
    Bensch, Suna
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Kutrib, Martin
    Institut fuer Informatik, Universität Giessen.
    Malcher, Andreas
    Institut fuer Informatik, Universität Giessen.
    Extended Uniformly Limited T0L Languages and Mild Context-Sensitivity2016In: Eight Workshop on Non-Classical Models of Automata and Applications (NCMA 2016): Short Papers / [ed] Henning Bordihn, Rudolf Freund, Benedek Nagy, and György Vaszil, Wien: Institut für Computersprachen , 2016, p. 35-46Conference paper (Refereed)
    Abstract [en]

    We study the fixed membership problem for k-uniformly-limited and propagating ET0L systems (kulEPT0L systems). To this end, the algorithm given in [7] is applied. It follows that kulEPT0L languages are parsable in polynomial time. Since kulEPT0L languages are semi-linear [1] and kulEPT0L systems generate certain non-context-free languages, which capture the non-context-free phenomena occurring in natural languages, this is the last building block to show that kulEPT0L languages, for k ≥ 2, belong to the family of mildly context-sensitive languages.

  • 19.
    Bergvik, David
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Designing experiences for virtual reality, in virtual reality: A design process evaluation2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Creating immersive experiences for virtual reality (VR) presents new design opportunities and challenges that do not appear when creating experiences on a screen. Creating prototypes and exploring concepts in VR is today limited to professionals with previous knowledge in 3D application development, and testing 3D experiences requires the usage of an Head-Mounted Display (HMD), which forces professionals to switch medium from the computer to an HMD. With new advances in this field, there have to be new solutions to these challenges. The goal of this thesis is to explore how VR technology can be utilized in the experience design process for VR. This is achieved through a literature study and conducting expert interviews, followed by a hardware evaluation of different HMDs and concept creation using rapid prototyping. From the interviews, a number of issues could be identified that correlates with the research from the literature study. Based on these findings, two phases were identified as suitable for further improvements; Concept prototyping and testing/tweaking of a created experience. Lo-fi and hi-fi prototypes of a virtual design tool were developed for HTC Vive and Google Daydream, which were selected based on the hardware evaluation. The prototypes are designed and developed, then tested using a Wizard of Oz approach. The purpose of the prototypes is to solve some of the issues when designing immersive experiences for HMDs in the suitable experience design phases that were identified by analyzing the interview results. An interactive testing suite for HTC Vive was developed for testing and evaluation of the final prototype, to verify the validity of the concept. Using Virtual Reality as a medium for designing virtual experiences is a promising way of solving current issues within this technological field that are identified in this thesis. Tools for object creation and manipulation will aid professionals when exploring new concepts as well as editing and testing existing immersive experiences. Furthermore, using a Wizard of Oz approach to test VR prototypes significantly improves the prototype quality without compromising the user experience in this medium. 

  • 20.
    Bohman, Dan
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Single Sign On med Azure AD Connect2016Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This report covers Azure AD Connect and Single/Simplified Sign On. Users and customers today places greater demand for easier login method and seamless experience for reaching all services. Microsoft has recently released Azure AD Connect tool to help synchronize passwords between Active Directory and the cloud services Office 365/Azure and 1000s of Software as a service applications. Team Norr IT-partner is an IT company that focuses on delivering Microsoft products to thier customers and therefore wanted to know more about Azure AD Connect. How to configure the solution and what the set requirements are.

    Single Sign On means that you only need to sign in with password and login once and automatically get access the applications that support the technology without any more credentials.  By using a Federated domain users get the best and safest experience with Single Sign On. Simplified Sign On lets users use the same username and password to login with to all applications with support, but no automatic login.

    Azure AD Connect tool installs the roles that are needed to run a Single Sign On or Simplified Sign On. By default the synchronization engine will keep track of information about the users and groups. Passwords are also synchronized between on-premises Active Directory and Azure Active Directory or federation server.

    What the Synchronization engine takes is determined by the rules defined. Password Sync does not install any extra server roles. With the Federation path there will be extra roles installed called Federation (AD FS) and Web Application Proxy (WAP). They handle the authentication of users instead of the normal Microsoft authentication. There is some set requirement for the servers that host the roles depending on the size of Active Directory and numbers of users. The servers need a certain base performance for it to work properly. 

  • 21.
    Bräne, Arvid
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    User Experience Design for Children: Developing and Testing a UX Framework2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Designing good digital experiences for children can be difficult; designers have to consider children's cognitive and motor skill limitations, understand their target audience, create something entertaining and educational, comply with national and international jurisdiction, and at the same time appeal to parents. We set out to create a general framework which designers and developers can use as a foundation and testing ground for their digital products in the field of user experience.

    The methods used during the thesis include interviews, literature studies, user testing, case studies, personas, prototyping, and more. The results created are primarily user experience guidelines packaged in a Theoretical Framework, user testing conclusions, along with suggestions on improving the current Lego Star Wars: Force Builders application, a few in the form of prototypes.

  • 22.
    Brännback, Andreas
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    FTTX-Analysverktyg anpassat för Telias nät2018Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    A tool for analyzing the status of Fiber to the X (FTTX) customers in Telia’s network has been programmed in the Python programming language. The system consists of a module divided structure where analysis functions of similar types are bundled into module files. The system is designed to be easily further developed by adding more analysis modules in future projects. To perform an analysis on a specific customer, the system retrieves technical data parameters from the switch which the customer is connected to, and compares these parameters against predetermined values to find deviations. Simple Network Management Protocol (SNMP) and Telnet are the primary protocols used to retrieve data. Hypertext Transfer Protocol (HTTP) is used to transfer data as system input and output. The result of an analysis is sent as Extensible Markup Language (XML) back to the server that originally requested the start of an analysis. The XML reply contains technical data parameters describing the customer’s connection status and an analytical response based on these technical parameters. The amount of data presented in the XML response varies slightly depending on the type of switch the customer is connected to. Switches of older hardware types generally presents less customer port data compared to more modern switches. Less customer port data leads to poor detail in the analytical response, and therefore, this analysis tool is better suited to the modern switches found in Telia's network.

  • 23.
    Buckland, Philip I.
    Umeå University, Faculty of Arts, Department of historical, philosophical and religious studies, Environmental Archaeology Lab.
    Freeing information to the people: Using the past to aid the future2011In: International Innovation - Disseminating Science Research and Technology, ISSN 2041-4552, no 4, p. 51-53Article in journal (Other (popular science, discussion, etc.))
    Abstract [en]

    Dr Philip Buckland discusses his recent project SEAD: the web-accessible scientific database that crosses archaeological and environmental disciplines. 

    Disciplines as diverse as anthropology and palaeoecology take an interest in our environment and how we have treated it. The Strategic Environmental Archaeology Database aims to create a multi-proxy, GIS-ready database for environmental and archaeological data to aid multidisciplinary research

  • 24.
    Camillo, Frédéric
    et al.
    University of Toulouse / ENSEEIHT.
    Caron, Eddy
    University of Lyon / École Normale Supérieure de Lyon.
    Guivarch, Ronan
    University of Toulouse / ENSEEIHT.
    Hurault, Aurélie
    University of Toulouse / ENSEEIHT.
    Klein, Cristian
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Pérez, Christian
    University of Lyon / INRIA.
    Resource Management Architecture for Fair Scheduling of Optional Computations2013In: 2013 Eighth International Conference on P2P, Parallel, Grid, Cloud and Internet Computing: 3PGCIC 2013 / [ed] Fatos Xhafa, Leonard Barolli, Dritan Nace, Salvatore Vinticinque and Alain Bui, IEEE Computer Society, 2013, p. 113-120Conference paper (Refereed)
    Abstract [en]

    Most HPC platforms require users to submit a pre-determined number of computation requests (also called jobs). Unfortunately, this is cumbersome when some of the computations are optional, i.e., they are not critical, but their completion would improve results. For example, given a deadline, the number of requests to submit for a Monte Carlo experiment is difficult to choose. The more requests are completed, the better the results are, however, submitting too many might overload the platform. Conversely, submitting too few requests may leave resources unused and misses an opportunity to improve the results.

    This paper introduces and solves the problem of scheduling optional computations. An architecture which auto-tunes the number of requests is proposed, then implemented in the DIET GridRPC middleware. Real-life experiments show that several metrics are improved, such as user satisfaction, fairness and the number of completed requests. Moreover, the solution is shown to be scalable.

  • 25.
    Chaudhry, Tanmay
    et al.
    SimScale GmbH, Germany.
    Doblander, Christoph
    Technische Universität München, Germany.
    Dammer, Anatol
    SimScale GmbH, Germany.
    Klein, Cristian
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Jacobsen, Hans-Arno
    Technische Universität München, Germany.
    Retrofitting Admission Control in an Internet-Scale Application2016Report (Other academic)
    Abstract [en]

    In this paper we propose a methodology to retrofit admission control in an Internet-scale, production application. Admission control requires less effort to improve the availability of an application, in particular when making it scalable is costly. This can occur due to the integration of 3rd-party legacy code or handling large amounts of data, and is further motivated by lean thinking, which argues for building a minimum viable product to discover customer requirements.

    Our main contribution consists in a method to generate an amplified workload, that is realistic enough to test all kinds of what-if scenarios, but does not require an exhaustive transition matrix. This workload generator can then be used to iteratively stress-test the application, identify the next bottleneck and add admission control.

    To illustrate the usefulness of the approach, we report on our experience with adding admission control within SimScale, a Software-as-a-Service start-up for engineering simulations, that already features 50,000 users.

  • 26.
    Daniel, Johansson
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Drivrutin för I/O-moduler tillhörande obsolet styr- och övervakningssystem2015Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The aim of this work was to solve the problem of compatibility between an old and a new control and monitoring system, when the previously used equipment has become obsolete and soon to be replaced by newer ones. The task was to create a driver for I/O-modules associated the control and monitoring system i30, in the new system JACE by producing documentation of the communication and then re-create it.Documentation of the communication was created by analysing the control and monitoring system i30 in a test environment while the signals were manually triggered. Verification of the documentation were made in the IDE for the new control and monitoring system JACE. With the tool Flex Serial Driver were the essential communication recreated and the layout of the driver was established. The graphical interface of the driver were developed with the user in mind by analyzing what the most frequently used functions were. The complete driver were created by the tool NDriver and programmed in the Java language.The result of the work is a complete documentation of the communication between the i30 and its I/O modules and a working driver with a scalable interface. The driver is not completely tested and are not ready for commercial use.

  • 27. Durango, Jonas
    et al.
    Dellkrantz, Manfred
    Maggio, Martina
    Klein, Cristian
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Papadopoulos, Alessandro Vittorio
    Hernandez-Rodriguez, Francisco
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Elmroth, Erik
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Arzen, Karl-Erik
    Control-theoretical load-balancing for cloud applications with brownout2014In: 2014 IEEE 53RD ANNUAL CONFERENCE ON DECISION AND CONTROL (CDC), 2014, p. 5320-5327Conference paper (Refereed)
    Abstract [en]

    Cloud applications are often subject to unexpected events like flash crowds and hardware failures. Without a predictable behaviour, users may abandon an unresponsive application. This problem has been partially solved on two separate fronts: first, by adding a self-adaptive feature called brownout inside cloud applications to bound response times by modulating user experience, and, second, by introducing replicas - copies of the applications having the same functionalities - for redundancy and adding a load-balancer to direct incoming traffic. However, existing load-balancing strategies interfere with brownout self-adaptivity. Load-balancers are often based on response times, that are already controlled by the self-adaptive features of the application, hence they are not a good indicator of how well a replica is performing. In this paper, we present novel load-balancing strategies, specifically designed to support brownout applications. They base their decision not on response time, but on user experience degradation. We implemented our strategies in a self-adaptive application simulator, together with some state-of-the-art solutions. Results obtained in multiple scenarios show that the proposed strategies bring significant improvements when compared to the state-of-the-art ones.

  • 28.
    Edvinsson, Joakim
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Webifiering av BidCon2014Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Consultec är ett ledande företag inom utveckling av IT-verktyg och tjänster anpassade för bygg- och installationsbranschen. De har identifierat ett behov från deras kunder att se över möjligheterna att göra ett av deras verktyg mer lättåtkomligt via en webb-applikation.Målet med detta projekt är att utvärdera om det är möjligt att publicera ett redan existerande program på en hemsida samt att ta fram en prototyp. Hemsidan som tagits fram visar ett grovt exempel över hur den färdiga produkten skulle kunna se ut.

  • 29.
    Ehatisham-ul-Haq, Muhammad
    et al.
    Faculty of Telecom and Information Engineering, University of Engineering and Technology, Taxila, Punjab, Pakistan.
    Awais Azam, Muhammad
    Faculty of Telecom and Information Engineering, University of Engineering and Technology, Taxila, Punjab, Pakistan.
    Naeem, Usman
    School of Architecture, Computing and Engineering, University of East London, United Kingdom.
    Ur Rèhman, Shafiq
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Khaild, Asra
    Department of Computer Science, COMSATS Institute of Information Technology, Wah Campus, Pakistan.
    Identifying smartphone users based on their activity patterns via mobile sensing2017In: Procedia Computer Science, ISSN 1877-0509, E-ISSN 1877-0509, Vol. 113, p. 202-209Article in journal (Refereed)
    Abstract [en]

    Smartphones are ubiquitous devices that enable users to perform many of their routine tasks anytime and anywhere. With the advancement in information technology, smartphones are now equipped with sensing and networking capabilities that provide context-awareness for a wide range of applications. Due to ease of use and access, many users are using smartphones to store their private data, such as personal identifiers and bank account details. This type of sensitive data can be vulnerable if the device gets lost or stolen. The existing methods for securing mobile devices, including passwords, PINs and pattern locks are susceptible to many bouts such as smudge attacks. This paper proposes a novel framework to protect sensitive data on smartphones by identifying smartphone users based on their behavioral traits using smartphone embedded sensors. A series of experiments have been conducted for validating the proposed framework, which demonstrate its effectiveness.

  • 30.
    Eklund, Patrik
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Kortelainen, Jari
    Two approaches to System-of-Systems from Lative Logic point of view2017In: 6TH INTERNATIONAL YOUNG SCIENTIST CONFERENCE ON COMPUTATIONAL SCIENCE, YSC 2017 / [ed] Klimova, A Bilyatdinova, A Kortelainen, J Boukhanovsky, A, Elsevier, 2017, Vol. 119, p. 16-21Conference paper (Refereed)
    Abstract [en]

    The paper presents two approaches to model System-of-Systems on lative logic point of view. Lative logic is a general framework to construct building blocks of logic using Category Theory as its metalanguage. This approach reveals avenues to describe System of -Systems themselves, and to model information and processes they posers, using some reasonable modelling languages in a computational manner, thus, touching foundations of computational science. After presenting some preliminary notes, the paper explains the main steps to construct lative logics, and then give two approaches to System-of-System modelling. Finally, the paper presents a survey to some applications.

  • 31.
    Eklund, Pauline
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Implementering av ISOBUS på ECU vid Ålö AB2017Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    A serial bus called ISOBUS based on CAN is becoming more and more common in the agriculture and forestry industry. The bus specifies communication between tractors and their implements. Earlier each implement had its own monitor to show its functionalities, which could lead to a lot of monitors in the tractor cabin. ISOBUS requires only one monitor, called VT (Virtual Terminal), regardless of the manufacturer of the implement.

    The aim of this thesis is to implement ISOBUS at Ålö’s ECU (Electronic Control Unit) so that it can present its functionalities to VT. The aim is to integrate a purchased third party commercial ISOBUS library on ECU. The amount of work to achieve ISOBUS compatibility without third party library shall be estimated, and if there is time the task shall also be carried out. An object pool based on Ålö’s existing interface shall be created, where the object pool is the graphical interface shown at VT. A demonstrator of ISOBUS VT shall be done.

    To implement the third party library hardware functions towards the CAN-bus was required. The hardware functions include receiving messages from a buffer and send messages directly on the bus. For the library to be alive and running it had to be initialized and a periodic call to the library had to be done. The result is that the library was implemented on ECU and data flows between ECU and VT.

    To achieve ISOBUS compatibility without third party library the existing protocol on Ålö’s ECU has to be removed by a base support for ISOBUS. Then a last part must be written to achieve full compatibility. Commands that the ISOBUS standard defines between ECU and VT has to be written, and callback functions that is called when VT sends commands to ECU. Management of answers and errors also have to be implemented. ISOBUS compatibility without third party library wasn’t carried out, but the amount of work was estimated and a general description of what has to be done is written. The conclusion is that it requires a lot of work and scrutiny of the standard. The advantage is that you get an insight into how the system works and the ability to influence functionalities yourself.

    The object pool design was based on Ålö’s existing interface. Menu systems was implemented, and a linear bar graph and a meter have the possibilities to show height and angle of the tractor loader bucket. Different ways to show a menu system has been discussed. The result is an object pool with the basic functions for Ålö’s interface, the demonstrator presents these functionalities. The interface for VT can be made quite similar to Ålö’s existing interface, with some differences such as fonts, image quality and menu functions.

  • 32.
    Emil, Ceder
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Detect misconnected Telia customers in the network2015Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Abstract

    The project consists of creating a program that can detect fiber customers that has been misconnected on the switch connecting them to the Telia network. The program will be able compare what customer is configured on the port against the customer who has received and the Telia router connected to the port. If there is a mismatch then there is a chance the customer has been misconnected.

    The comparison can be done because the unique serial number of the Telia router is both registered in the session database over active Telia routers and also in the database of products delivered to customers. This will only work on customers with Telia routers, but it will still be helpful as it would give an indication of what switches might have misconnect customers. If there is one misconnected customer on a switch there is likely to be more.

    The program was created with MySQL and PHP in the form of a web tool. The program can be run against certain switches or the program can be run against all active Telia routers and look for mismatches.

    To make the program work it required access to the session database over active Telia routers, the database over customer configuration on the port and the database over Telia routers sent to customers. These are three different systems and because of the time constraint only a part of the data was used or retrieved from testing environments.

    With the available data the program could do the comparison against 8627 customers and of those 303 customers had a mismatch in the comparison. This does not necessarily mean that all of them are misconnected. In most cases it was another person in the household receiving the Telia router than the person that was signed up on Telia services. This could be sort out by ensuring that the person receiving the Telia router also was signed up to a Telia service. This left 57 customers out of the 303. Out of those 57 customers a part of them had special services and some had split the services on two persons in one household. After sorting them out manually there was around 15 customers left who was likely misconnected

    There is still no way to be certain those 15 customer are misconnected, however there a possibility they are and if there are several mismatches on a single switch it is certainly worth investigating further as it is a large possibility there are misconnected customers.

  • 33. Farokhi, Soodeh
    et al.
    Lakew, Ewnetu Bayuh
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Klein, Cristian
    Brandic, Ivona
    Elmroth, Erik
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Coordinating CPU and Memory Elasticity Controllers to Meet Service Response Time Constraints2015In: 2015 INTERNATIONAL CONFERENCE ON CLOUD AND AUTONOMIC COMPUTING (ICCAC), 2015, p. 69-80Conference paper (Refereed)
    Abstract [en]

    Vertical elasticity is recognized as a key enabler for efficient resource utilization of cloud infrastructure through fine-grained resource provisioning, e.g., allowing CPU cycles to be leased for as short as a few seconds. However, little research has been done to support vertical elasticity where the focus is mostly on a single resource, either CPU or memory, while an application may need arbitrary combinations of these resources at different stages of its execution. Nonetheless, the existing techniques cannot be readily used as-is without proper orchestration since they may lead to either under-or over-provisioning of resources and consequently result in undesirable behaviors such as performance disparity. The contribution of this paper is the design of an autonomic resource controller using a fuzzy control approach as a coordination technique. The novel controller dynamically adjusts the right amount of CPU and memory required to meet the performance objective of an application, namely its response time. We perform a thorough experimental evaluation using three different interactive benchmark applications, RUBiS, RUBBoS, and Olio, under workload traces generated based on open and closed system models. The results show that the coordination of memory and CPU elasticity controllers using the proposed fuzzy control provisions the right amount of resources to meet the response time target without over-committing any of the resource types. In contrast, with no coordinating between controllers, the behaviour of the system is unpredictable e.g., the application performance may be met but at the expense of over-provisioning of one of the resources, or application crashing due to severe resource shortage as a result of conflicting decisions.

  • 34.
    Forsberg, Evelina
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Enterprise Voice Simulation (EVS) för mobila enheter i BYOD miljö.2014Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This report introduces the Umeå University background to the introduction of Lync Server 2013 stable established in 2014. The wireless network at Umeå University used by students and employees with mobile devices such as smartphones and laptops. The throughput into the wireless network is affected by different types of traffics from various devices in whole network infrastructure. This report covered closer glance at "Voice UDP" and "Lync Enterprise Voice" with a focus on congestion control for transfers of RTP traffic between mobile clients and 802.11 to identify the quality of a Lync call, "VoIP over WLAN”. The method is based on references with MOS scale of 1 to 5 in order to compare which mobile device should qualify for best achieved Quality of Experience. The results of the eight selected mobile devices showed that the Samsung Galaxy s2 topped the overall benchmark for minimum dropped and most passed packets. The iPhone 5 resulted in the worst mobile device for RTP traffic with the most amount of lost packets and the lowest amount of passing packets.Benchmark:Benchmark measured by the total summation of percent and pmeasurement references, Voice MOS, packet loss, maximum Consecutive

  • 35.
    Gaggl, Sarah Alice
    et al.
    Technische Universität Dresden, Germany.
    Nieves, Juan CarlosUmeå University, Faculty of Science and Technology, Department of Computing Science.Strass, HannesUniversity of Leipzig, Germany.
    Arg-LPNMR 2016 proceedings: First International Workshop on Argumentation in Logic Programming and Non-Monotonic Reasoning2016Collection (editor) (Refereed)
    Abstract [en]

    This volume contains the papers presented at Arg-LPNMR 2016: First International Workshop on Argumentation in Logic Programming and Nonmonotonic Reasoning held on July 8-10, 2016 in New York City, NY.

  • 36.
    Gaggl, Sarah Alice
    et al.
    Technische Universität Dresden, Germany.
    Nieves, Juan Carlos
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Strass, Hannes
    Leipzig University, Germany.
    Torroni, Paolo
    University of Bologna, Italy.
    Preface: Argumentation and Logic Programming (Revised Selected Papers of ArgLP 2015)2017In: Fundamenta Informaticae, ISSN 0169-2968, E-ISSN 1875-8681, Vol. 155, no 3Article in journal (Other academic)
  • 37.
    Goggins, Sean P
    et al.
    Drexel University, USA.
    Jahnke, Isa
    Umeå University, Faculty of Social Sciences, Department of applied educational science, Interactive Media and Learning (IML).
    CSCL@work: making learning visible in unexpected online places across established boundaries2012In: International Journal of Sociotechnology and Knowledge Development, ISSN 1941-6253, Vol. 4, no 3, p. 17-37Article in journal (Refereed)
    Abstract [en]

    We introduce Computer-Supported Collaborative Learning (CSCL) at the workplace (CSCL@Work) as a conceptual framework for bridging the knowledge of researchers in the field of CSCL to work-based learning. Research in the field of Organizational Learning emerged in 1978, and gained further attention in the 1990’s when challenges centered on the creation of organizational cultures to support existing knowledge sharing. In contemporary firms, shepherding the creation of new knowledge is of equal importance, and is driven by two primary research questions. First, how do organizations create new knowledge when the answer to a particular problem is not available within the firm? Second, what cultures of learning must and do exist to support solving problems when the answer is not known within an organization? Contemporary answers to these questions must recognize that learning is an implicit, often invisible component of work, and explicitly decouple the construct of learning from its main western institutionalization, the school. To advance thinking in this area, we undertook a meta analysis of 8 CSCL@Work cases and developed 3 design theses: 1) Learning occurs in unexpected and unusual online learning places, especially through Social Media. 2) Learning activities incorporate feedback from diverse people, who are not available within traditional organizational boundaries; 3) learning must be made visible across established boundaries. Designing explicit construction of new knowledge needs to be integrated into workplace practices today through pedagogical and technological design.

  • 38. Goumas, Georgios
    et al.
    Nikas, Konstantinos
    Lakew, Ewnetu Bayuh
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Kotselidis, Christos
    Attwood, Andrew
    Elmroth, Erik
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Flouris, Michail
    Foutris, Nikos
    Goodacre, John
    Grohmann, Davide
    Karakostas, Vasileios
    Koutsourakis, Panagiotis
    Kersten, Martin
    Lujan, Mikel
    Rustad, Einar
    Thomson, John
    Tomás, Luis
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Vesterkjaer, Atle
    Webber, Jim
    Zhang, Ying
    Koziris, Nectarios
    ACTiCLOUD: Enabling the Next Generation of Cloud Applications2017In: 2017 IEEE 37TH INTERNATIONAL CONFERENCE ON DISTRIBUTED COMPUTING SYSTEMS (ICDCS 2017) / [ed] Lee, K Liu, L, IEEE Computer Society, 2017, p. 1836-1845Conference paper (Refereed)
    Abstract [en]

    Despite their proliferation as a dominant computing paradigm, cloud computing systems lack effective mechanisms to manage their vast amounts of resources efficiently. Resources are stranded and fragmented, ultimately limiting cloud systems' applicability to large classes of critical applications that pose non-moderate resource demands. Eliminating current technological barriers of actual fluidity and scalability of cloud resources is essential to strengthen cloud computing's role as a critical cornerstone for the digital economy. ACTiCLOUD proposes a novel cloud architecture that breaks the existing scale-up and share-nothing barriers and enables the holistic management of physical resources both at the local cloud site and at distributed levels. Specifically, it makes advancements in the cloud resource management stacks by extending state-of-the-art hypervisor technology beyond the physical server boundary and localized cloud management system to provide a holistic resource management within a rack, within a site, and across distributed cloud sites. On top of this, ACTiCLOUD will adapt and optimize system libraries and runtimes (e.g., JVM) as well as ACTiCLOUD-native applications, which are extremely demanding, and critical classes of applications that currently face severe difficulties in matching their resource requirements to state-of-the-art cloud offerings.

  • 39.
    Hegner, Stephen
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Characterization of optimal complements of database views defined by projection2011In: Semantics in Data and Knowledge Bases: 4th International Workshop, SDKB 2010, Bordeaux, France, July 5, 2010, Revised Selected Papers / [ed] Klaus-Dieter Schewe and Bernhard Thalheim, Berlin: Springer Berlin/Heidelberg, 2011, p. 73-95Conference paper (Refereed)
  • 40.
    Hegner, Stephen
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    FD Covers and Universal Complements of Simple Projections2012In: Foundations of Information and Knowledge Systems -: 7th International Symposium, FoIKS 2012, Kiel, Germany, March 5-9, 2012. Proceedings / [ed] Thomas Lukasiewicz, Attila Sali, Heidelberg: Springer Berlin/Heidelberg, 2012, p. 184-202Conference paper (Refereed)
    Abstract [en]

    The constant-complement strategy, in which the admissible updates to a given view are those which hold a second complementary view constant, remains one of the most attractive formalisms for identifying suitable translation mechanisms for updates to views of database schemata. However, in general, it suffers from the drawback that the reflections of view updates to the main schema can depend upon the choice of complement in various ways. To overcome this drawback completely, a special kind of complement, called a universal complement, is required. In this paper, sufficient conditions for the existence of such a complement are established for a classical but nevertheless very important setting — views defined by simple projection of a universal relational schema constrained by functional dependencies (FDs). Certain uniqueness properties of covers of these dependencies prove critical in the characterization. The results are extended to quasi-universal complements, which are unique up to exchange of equivalent attributes, thus recapturing certain situations for which unique covers do not exist.

  • 41.
    Hegner, Stephen
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Independent Update Reflections on Interdependent Database Views2012In: Conceptual Modelling and Its Theoretical Foundations: Essays Dedicated to Bernhard Thalheim on the Occasion of His 60th Birthday / [ed] Antje Düsterhöft, Meike Klettke, Klaus-Dieter Schewe, Heidelberg: Springer Berlin/Heidelberg, 2012, p. 101-115Chapter in book (Refereed)
    Abstract [en]

    The problem of identifying suitable view-update strategies is typically addressed in the context of a single view. However, it is often the case that several views must co-exist; the challenge is then to find strategies which allow one view to be updated without affecting the other. The classical constant-complement strategy can provide a solution to this problem; however, both the context and the admissible updates are quite limited. In this work, the updates which are possible within this classical approach are extended substantially via a technique which considers only the states which are reachable from a given initial configuration. The results furthermore do not depend upon complementation, and thus are readily extensible to settings involving more than two views.

  • 42.
    Hegner, Stephen
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Information-based distance measures and the canonical reflection of view updates2011In: Annals of Mathematics and Artificial Intelligence, ISSN 1012-2443, E-ISSN 1573-7470, Vol. 63, no 3-4, p. 317-355Article in journal (Refereed)
    Abstract [en]

    For the problem of reflecting an update on a database view to the main schema, the constant-complement strategies are precisely those which avoid all update anomalies, and so define the gold standard for well-behaved solutions to the problem. However, the families of view updates which are supported under such strategies are limited, so it is sometimes necessary to go beyond them, albeit in a systematic fashion. In this work, an investigation of such extended strategies is initiated for relational schemata. The approach is to characterize the information content of a database instance, and then require that the optimal reflection of a view update to the main schema embody the least possible change of information. The key property is identified to be strong monotonicity of the view, meaning that view insertions may always be reflected as insertions to the main schema, and likewise for deletions. In that context it is shown that for insertions and deletions, an optimal update, entailing the least change of information, exists and is unique up to isomorphism for wide classes of constraints.

  • 43.
    Henriksson, Alexander
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Utvecklingsprojekt för produktionsverktyg i kulturverksamhet: Database development in a cultural environment2015Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The project is an example of developing a relational database that is cross-platform and easy to maintain and develop in the future without a lot of programming knowledge. The system is created in Filemaker Pro 13/14 which also serves as the client for Mac OS X and the client for mobile devices is Filemaker Go 13/14.

    The employees at the costume department at NorrlandsOperan have in the past worked primarily with Word and Excel documents in a shared fileserver environment. Some problems with this kind of solution are regarding documentation, finding information and working on the go.

    The solution is inteded to give the employees a logical order in which to do regular processes involved in a production as well as to add relevant data to these processes. Searching for information is easy and flexible. The data about the performers in the production is easy to use in new productions and the data carries over from one production to the next. Another feature is the ability to search for costumes that a performer will use in a production and also to view information about which scene the costumes are being used. 

  • 44.
    Ibidunmoye, Olumuyiwa
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Performance anomaly detection and resolution for autonomous clouds2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Fundamental properties of cloud computing such as resource sharing and on-demand self-servicing is driving a growing adoption of the cloud for hosting both legacy and new application services. A consequence of this growth is that the increasing scale and complexity of the underlying cloud infrastructure as well as the fluctuating service workloads is inducing performance incidents at a higher frequency than ever before with far-reaching impact on revenue, reliability, and reputation. Hence, effectively managing performance incidents with emphasis on timely detection, diagnosis and resolution has thus become a necessity rather than luxury. While other aspects of cloud management such as monitoring and resource management are experiencing greater automation, automated management of performance incidents remains a major concern.

    Given the volume of operational data produced by cloud datacenters and services, this thesis focus on how data analytics techniques can be used in the aspect of cloud performance management. In particular, this work investigates techniques and models for automated performance anomaly detection and prevention in cloud environments. To familiarize with developments in the research area, we present the outcome of an extensive survey of existing research contributions addressing various aspects of performance problem management in diverse systems domains. We discuss the design and evaluation of analytics models and algorithms for detecting performance anomalies in real-time behaviour of cloud datacenter resources and hosted services at different resolutions. We also discuss the design of a semi-supervised machine learning approach for mitigating performance degradation by actively driving quality of service from undesirable states to a desired target state via incremental capacity optimization. The research methods used in this thesis include experiments on real virtualized testbeds to evaluate aspects of proposed techniques while other aspects are evaluated using performance traces from real-world datacenters.

    Insights and outcomes from this thesis can be used by both cloud and service operators to enhance the automation of performance problem detection, diagnosis and resolution. They also have the potential to spur further research in the area while being applicable in related domains such as Internet of Things (IoT), industrial sensors as well as in edge and mobile clouds.

  • 45.
    Ibidunmoye, Olumuyiwa
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Performance problem diagnosis in cloud infrastructures2016Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Cloud datacenters comprise hundreds or thousands of disparate application services, each having stringent performance and availability requirements, sharing a finite set of heterogeneous hardware and software resources. The implication of such complex environment is that the occurrence of performance problems, such as slow application response and unplanned downtimes, has become a norm rather than exception resulting in decreased revenue, damaged reputation, and huge human-effort in diagnosis. Though causes can be as varied as application issues (e.g. bugs), machine-level failures (e.g. faulty server), and operator errors (e.g. mis-configurations), recent studies have attributed capacity-related issues, such as resource shortage and contention, as the cause of most performance problems on the Internet today. As cloud datacenters become increasingly autonomous there is need for automated performance diagnosis systems that can adapt their operation to reflect the changing workload and topology in the infrastructure. In particular, such systems should be able to detect anomalous performance events, uncover manifestations of capacity bottlenecks, localize actual root-cause(s), and possibly suggest or actuate corrections.

    This thesis investigates approaches for diagnosing performance problems in cloud infrastructures. We present the outcome of an extensive survey of existing research contributions addressing performance diagnosis in diverse systems domains. We also present models and algorithms for detecting anomalies in real-time application performance and identification of anomalous datacenter resources based on operational metrics and spatial dependency across datacenter components. Empirical evaluations of our approaches shows how they can be used to improve end-user experience, service assurance and support root-cause analysis. 

  • 46.
    Ibidunmoye, Olumuyiwa
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Ali-Reza, Rezaie
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Elmroth, Erik
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Adaptive Anomaly Detection in Performance Metric Streams2018In: IEEE Transactions on Network and Service Management, ISSN 1932-4537, E-ISSN 1932-4537, Vol. 15, no 1, p. 217-231Article in journal (Refereed)
    Abstract [en]

    Continuous detection of performance anomalies such as service degradations has become critical in cloud and Internet services due to impact on quality of service and end-user experience. However, the volume and fast changing behaviour of metric streams have rendered it a challenging task. Many diagnosis frameworks often rely on thresholding with stationarity or normality assumption, or on complex models requiring extensive offline training. Such techniques are known to be prone to spurious false-alarms in online settings as metric streams undergo rapid contextual changes from known baselines. Hence, we propose two unsupervised incremental techniques following a two-step strategy. First, we estimate an underlying temporal property of the stream via adaptive learning and, then we apply statistically robust control charts to recognize deviations. We evaluated our techniques by replaying over 40 time-series streams from the Yahoo! Webscope S5 datasets as well as 4 other traces of real web service QoS and ISP traffic measurements. Our methods achieve high detection accuracy and few false-alarms, and better performance in general compared to an open-source package for time-series anomaly detection.

  • 47.
    Ibidunmoye, Olumuyiwa
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Elmroth, Erik
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Blackbox Strategies for Detecting Service Performance Anomalies in Virtualized Environments2016Report (Other academic)
    Abstract [en]

    In order to prevent violation of service-level objectives and to guarantee good user experience, detection of symptoms such as slow application response, degraded transaction throughput, and service outages, is crucial. We propose a black-box approach for detecting such symptoms in service performance behaviour without intrusive application instrumentation. In case a known baseline behaviour exists, we employ kernel density estimation to discover deviations from a given set of baseline measurements. Conversely, when no baseline exists, we apply statistical process control charts on prediction errors obtained from Holt-Winter’s double exponential smoothing to identify anomalies in metric time-series. We evaluate our methods on tail response times traces collected from experiments conducted in a real testbed under realistic load and fault injections. Results show the applicability of our approach for improving service assurance and also demonstrate how service level anomalies correlate with system-level events such as resource contention and bottlenecks.

  • 48.
    Ibidunmoye, Olumuyiwa
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Francisco, Hernandez-Rodriguez
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Elmroth, Erik
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Performance Anomaly Detection and Bottleneck Identification2015In: ACM Computing Surveys, ISSN 0360-0300, E-ISSN 1557-7341, Vol. 48, no 1, article id 4Article in journal (Refereed)
    Abstract [en]

    In order to meet stringent performance requirements, system administrators must effectively detect undesirable performance behaviours, identify potential root causes and take adequate corrective measures. The problem of uncovering and understanding performance anomalies and their causes (bottlenecks) in different system and application domains is well studied. In order to assess progress, research trends and identify open challenges, we have reviewed major contributions in the area and present our findings in this survey. Our approach provides an overview of anomaly detection and bottleneck identification research as it relates to the performance of computing systems. By identifying fundamental elements of the problem, we are able to categorize existing solutions based on multiple factors such as the detection goals, nature of applications and systems, system observability, and detection methods.

  • 49.
    Ibidunmoye, Olumuyiwa
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Lakew, Ewnetu Bayuh
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Elmroth, Erik
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    A Black-box Approach for Detecting Systems Anomalies in Virtualized Environments2017In: 2017 IEEE International Conference on Cloud and Autonomic Computing (ICCAC 2017), IEEE, 2017, p. 22-33Conference paper (Refereed)
    Abstract [en]

    Virtualization technologies allow cloud providers to optimize server utilization and cost by co-locating services in as few servers as possible. Studies have shown how applications in multi-tenant environments are susceptible to systems anomalies such as abnormal resource usage due to performance interference. Effective detection of such anomalies requires techniques that can adapt autonomously with dynamic service workloads, require limited instrumentation to cope with diverse applications services, and infer relationship between anomalies non-intrusively to avoid "alarm fatigue" due to scale. We propose a black-box framework that includes an unsupervised prediction-based mechanism for automated anomaly detection in multi-dimensional resource behaviour of datacenter nodes and a graph-theoretic technique for ranking anomalous nodes across the datacenter. The proposed framework is evaluated using resource traces of over 100 virtual machines obtained from a production cluster as well as traces obtained from an experimental testbed under realistic service composition. The technique achieve average normalized root mean squared forecast error and R^2 of (0.92, 0.07) across hosts servers and (0.70, 0.39) across virtual machines. Also, the average detection rate is 88% while explaining 62% of SLA violations with an average lead-time of 6 time-points when the testbed is actively perturbed under three contention scenarios. 

  • 50.
    Ibidunmoye, Olumuyiwa
    et al.
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Metsch, Thijs
    Intel Labs Europe, Collingstown Industrial Park, Leixlip, Ireland.
    Bayon-Molino, Victor
    Intel Labs Europe, Collingstown Industrial Park, Leixlip, Ireland.
    Elmroth, Erik
    Umeå University, Faculty of Science and Technology, Department of Computing Science.
    Performance Anomaly Detection using Datacenter Landscape Graphs2017Conference paper (Other academic)
    Abstract [en]

    The migration of mission-critical workloads to the cloud and the automation of various aspects of datacenter management is contributing to the evolution of software-defined infrastructures. One implication of this evolution is that the composition (both physical and virtual) and logical topology of datacenters is becoming even more dynamic. Identification of performance problems (e.g.\ bottlenecks) in such environments needs to be done with awareness of this dynamic topology to understand the impact of dependencies among components. A technique is introduced that a) employs expert knowledge to identify bottleneck components using associated performance metrics, and b) utilizes dynamic dependencies to rank problem components in order to facilitate diagnosis efforts. The technique is demonstrated experimentally on an OpenStack testbed with realistic fault injection. Results of experiment case studies show that the technique is able to correctly detect and rank problem nodes. 

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