Imperial College London

ProfessorWilliamKnottenbelt

Faculty of EngineeringDepartment of Computing

Professor of Applied Quantitative Analysis
 
 
 
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Contact

 

+44 (0)20 7594 8331w.knottenbelt Website

 
 
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Location

 

E363ACE ExtensionSouth Kensington Campus

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Summary

 

Publications

Publication Type
Year
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182 results found

Anastasiou N, Knottenbelt WJ, 2013, Deriving Coloured Generalised Stochastic Petri Net Performance Models from High-Precision Location Tracking Data, 4th ACM/SPEC International Conference on Performance Engineering (ICPE 2013), Publisher: ACM, Pages: 375-386

Stochastic performance models are widely used to analyse the performability of systems that involve the flow and processing of customers and resources. However, model formulation and parameterisation are traditionally manual and thus expensive, intrusive and error-prone. Our earlier work has demonstrated the feasibility of automated performance model construction from location tracking data. In particular, we presented a methodology based on a four-stage data processing pipeline, which automatically constructs Generalised Stochastic Petri Net}(GSPN) performance models from an input dataset consisting of raw location tracking traces. This pipeline was subsequently enhanced with a presence-based synchronisation detection mechanism.This paper introduces Coloured Generalised Stochastic Petri Nets (CGSPNs) into our methodology in order to provide support for multiple customer classes and service cycles. Distinct token types are used to model customers of different classes, while Johnson's algorithm for enumerating elementary cycles in a directed graph is employed to detect the presence of service cycles. Coloured tokens are also used to accurately reflect customer routing after the completion of a service cycle. A third extension enables the calculation and representation of the inter-routing probability of the customer flowbetween the system's service centres. We evaluate these extensions and their integration in our existing methodology via a case study ofa simplified model of an Accident and Emergency (A&E) department. The case study is based onsynthetic location tracking data, generated using an extended version of the LocTrackJINQS location-aware queueing network simulator.

Conference paper

Nika M, Ivanova G, Knottenbelt WJ, 2013, On celebrity, epidemiology and the internet, Pages: 175-183

Copyright © 2014 ICST. The proliferation of the internet has created new opportunities to study the mechanisms behind the emergence and dynamic behaviour of online popularity and celebrity. In this paper we examine how common epidemic models, specifically SIR and SEIR models, can be applied to model the evolution of outbreaks of celebrity interest on the internet. A major challenge when using such models is to parameterise them to fit data as an outbreak unfolds over time, without knowing the initial number of susceptibles in the target population. We present a methodology capable of fitting the model's parameters from a single trace, while the outbreak unfolds, and of forecasting the epidemic's progression in the coming days. We present results on three kinds of data: simulated epidemic data, data from a real Influenza virus outbreak and data from music artists BitTorrent download and YouTube video views activity.

Conference paper

Huang W-C, Knottenbelt WJ, 2013, Self-Adaptive Containers: Building Resource-Efficient Applications with Low Programmer Overhead, 8th International Symposium on Software Engineering for Adaptive and Self-Managing Systems (SEAMS), Publisher: IEEE, Pages: 123-132

Conference paper

, 2013, Computer Performance Engineering - 10th European Workshop, EPEW 2013, Venice, Italy, September 16-17, 2013. Proceedings, Publisher: Springer

Conference paper

Tsimashenka I, Knottenbelt WJ, 2013, Reduction of Subtask Dispersion in Fork-Join Systems., Publisher: Springer, Pages: 325-336

Conference paper

Anastasiou N, Knottenbelt WJ, 2013, PEPERCORN: Inferring Performance Models from Location Tracking Data., Publisher: Springer, Pages: 169-172

Conference paper

Kolodziej J, Knottenbelt WJ, Khan SU, 2012, Theory and Practice of Stochastic Modelling Preface, COMPUTERS & MATHEMATICS WITH APPLICATIONS, Vol: 64, Pages: 3657-3657, ISSN: 0898-1221

Journal article

Knottenbelt WJ, Spanias D, Madurska AM, 2012, A common-opponent stochastic model for predicting the outcome of professional tennis matches, COMPUTERS & MATHEMATICS WITH APPLICATIONS, Vol: 64, Pages: 3820-3827, ISSN: 0898-1221

Journal article

Osman R, Knottenbelt WJ, 2012, Database system performance evaluation models: A survey, PERFORMANCE EVALUATION, Vol: 69, Pages: 471-493, ISSN: 0166-5316

Journal article

Leung TLY, Knottenbelt WJ, 2012, Comparative Evaluation of Independent Private Values Distributions on Internet Auction Performance, International Journal of E-Entrepreneurship and Innovation, Vol: 3, Pages: 59-71, ISSN: 1947-8585

<jats:p>The Independent Private Values (IPV) model is foundational for the analysis of Internet auction performance and is widely used in the study of auction behaviour. The characteristics of this model include the assumptions of privacy and independence where the value of the commodity in question is private to the individual buyers, and that different buyers do not know the values other buyers attached to the commodity. In addition, these values are drawn from a common distribution which is known to the buyers. In probabilistic terms, this essentially amounts to a series of values which are independent and identically distributed. The features and characteristics of the IPV distribution will have a significant impact on auction behaviour, and since a general stochastic analysis of their impact is analytically intractable, here auction performance is studied using an auction process simulator. Both hard close and soft close Internet auctions are studied. In addition, Vickrey auctions and auction mechanisms with multiple bid acceptance are compared and evaluated. From experimental findings, the paper establishes quantitative relationships between the different auction process parameters, deploy suitable IPV distributions to model the characteristics of different communities of bidders, provide suggestions for optimising auction performance, and recommend strategies for efficient auction design.</jats:p>

Journal article

Dingle NJ, Knottenbelt WJ, Spanias D, 2012, On the (Page) Ranking of Professional Tennis Players., Publisher: Springer, Pages: 237-247

Conference paper

Tsimashenka I, Knottenbelt WJ, Harrison PG, 2012, Controlling Variability in Split-Merge Systems., Publisher: Springer, Pages: 165-177

Conference paper

Malony AD, Karatza HD, Knottenbelt WJ, McKee Set al., 2012, Topic 2: Performance Prediction and Evaluation., Publisher: Springer, Pages: 52-53

Conference paper

Zhang X, Ai Z, Yarlagadda P, Kim YHet al., 2011, Preface, ISSN: 1022-6680

Conference paper

Tsirimpas P, Knottenbelt WJ, 2011, SPORTSBET: A tool for the quantitative evaluation and execution of betting exchange trading strategies, Pages: 155-156

Betting exchange markets, which offer person-to-person betting, have attracted increasing interest due to their similarities with financial markets and their growing economic importance. This paper presents SPORTSBET, an event-driven tool for the quantitative evaluation of betting exchange trading strategies. It was developed to specify, execute and back-test parameterised betting strategies for a wide range of sports. SPORTSBET allows the definition of betting strategies in an extended version of the UrbiScript language as sets of concurrent processes which make use of event-calculus-like operators. Strategy performance is quantified by synchronizing multiple real time or historical data streams with a dynamic market reconstruction. © 2011 IEEE.

Conference paper

Leung TLY, Knottenbelt WJ, 2011, Stochastic Modelling and Optimisation of Internet Auction Processes, Electronic Notes in Theoretical Computer Science, Vol: 275, Pages: 105-121, ISSN: 1571-0661

Internet auctions are an attractive mechanism for the exchange of goods at a non-fixed price point. The operation of these auctions can be run under a variety of parameters. In this paper, we provide a theoretical analysis of fixed time forward auctions in cases where a single bid or multiple bids are accepted in a single auction. A comparison of the economic benefits and the corresponding buyer and seller surpluses between the auctions where a single bid is accepted and the auctions where multiple bids are accepted is made. These models are verified through systematic simulation experiments, based on a series of operational assumptions, which characterise the arrival rate of bids, as well as the distribution from which the private values of buyers are sampled. Decision rules for optimising surplus under different auction fee structures are also given. © 2011 Elsevier B.V.

Journal article

Horng T-C, Anastasiou N, Field T, Knottenbelt Wet al., 2011, LocTrackJINQS: An Extensible Location-aware Simulation Tool for Multiclass Queueing Networks, Electronic Notes in Theoretical Computer Science, Vol: 275, Pages: 93-104, ISSN: 1571-0661

Journal article

Leung TLY, Knottenbelt WJ, 2011, Consumer-to-Consumer Internet Auction Models, International Journal of Online Marketing, Vol: 1, Pages: 17-28, ISSN: 2156-1753

<jats:p>Internet auctions have become an increasingly common method for exchanging goods and services across the world both among consumers themselves, as well as between businesses and consumers. These Internet auction mechanisms have the scope of incorporating procedures of much greater complexity and variety, and they exhibit characteristics and properties that are quite distinct from conventional auctions. In this paper, the authors provide an experimental study of the performance characteristics and operational behaviour of a number of online auction models, including the fixed time forward auctions, the Vickrey auctions, and models with soft close variable auction times. These online auction models are studied through systematic simulation experiments, based on a series of operational assumptions, which characterize the arrival rate of bids, as well as the distribution from which the private values of buyers are sampled. Suggestions for efficient online auction design and procedures for improving auction performance are given, and the behaviour of the average auction income and average auction duration are quantified and compared.</jats:p>

Journal article

Lebrecht AS, Dingle NJ, Knottenbelt WJ, 2011, Analytical and Simulation Modelling of Zoned RAID Systems, COMPUTER JOURNAL, Vol: 54, Pages: 691-707, ISSN: 0010-4620

Journal article

Franciosi F, Knottenbelt W, 2011, Data allocation strategies for the management of Quality of Service in Virtualised Storage Systems, 2011 IEEE 27th Symposium on Mass Storage Systems and Technologies (MSST), Publisher: IEEE

Conference paper

Knottenbelt WJ, Lebrecht AS, Dingle NJ, 2011, Performance Models of Zoned Disk Arrays, Editors: Ivanyi, Topping, Publisher: Saxe-Coburg Publications, Pages: 105-134

Book chapter

Guenther MC, Dingle NJ, Bradley JT, Knottenbelt WJet al., 2011, Passage-time computation and aggregation strategies for large semi-Markov processes, PERFORMANCE EVALUATION, Vol: 68, Pages: 221-236, ISSN: 0166-5316

Journal article

Tsimashenka I, Knottenbelt WJ, 2011, Reduction of variability in split-merge systems., Publisher: Imperial College London, Pages: 101-107

Conference paper

Anastasiou N, Horng T-C, Knottenbelt WJ, 2011, Deriving generalised stochastic Petri net performance models from high-precision location tracking data., Publisher: ICST/ACM, Pages: 91-100

Conference paper

Anastasiou N, Knottenbelt WJ, Marin A, 2011, Automatic Synchronisation Detection in Petri Net Performance Models Derived from Location Tracking Data., Publisher: Springer, Pages: 29-41

Conference paper

Leung TLY, Knottenbelt WJ, 2011, The Effect of Private Valuation on E-Auction Revenues., Publisher: Springer, Pages: 229-242

Conference paper

Mason AM, Dingle NJ, Knottenbelt WJ, Bell D, Buchanan W, Thuemmler Cet al., 2010, Modelling infection spread using location tracking, International Journal of Healthcare Technology and Management, Vol: 11, Pages: 442-461, ISSN: 1368-2156

The precision of location tracking technology has improved greatly over the last few decades. We aim to show that by tracking the locations of individuals in a closed environment, it is now possible to record the nature and frequency of interactions between them. Further, that it is possible to use such data to predict the way in which an infection will spread throughout such a population, given parameters such as transmission and recovery rates. We accordingly present a software package that is capable of recording and then replaying location data provided by a high-precision location tracking system. The software then employs a combination of SIR modelling and the epidemiological technique of contact tracing in order to predict the spread of an infection. We use this software to conduct a number of experiments using a sample data set, and compare the SIR graphs generated from these to similar graphs generated using the traditional SIR differential equations. Copyright © 2010 Inderscience Enterprises Ltd.

Journal article

Kulatunga H, Knottenbelt WJ, Kadirkamanathan V, 2010, Adaptive Planning of Staffing Levels in Health Care Organisations, 2nd Congress on Electronic Healthcare for the 21st Century, Publisher: SPRINGER-VERLAG BERLIN, Pages: 88-+, ISSN: 1867-8211

Conference paper

, 2010, Analytical and Stochastic Modeling Techniques and Applications, 17th International Conference, ASMTA 2010, Cardiff, UK, June 14-16, 2010. Proceedings, Publisher: Springer

Conference paper

, 2009, Proceedings of MASCOTS 2009, 17th Annual Meeting of the IEEE/ACM International Symposium on Modelling, Analysis and Simulation of Computer and Telecommunication Systems, MASCOTS 2009, International Symposium on Modelling, Analysis and Simulation of Computer and Telecommunication Systems, Imperial College London, Publisher: IEEE Computer Society Press

Message from the Programme Committee Chairs\r\n\r\nOn behalf of the Organising and Programme Committee, it is our pleasure to present to you the proceedings of MASCOTS 2009, the IEEE Computer SocietyÆs 17th International Symposium on Modeling, Analysis and Simulation of Computer and Telecommunications Systems, which will be held in London. Our society is ever more dependent on the reliable and high performance operation of complex combinations of computer and communication technologies. As existing technologies evolve and new ones emerge, it remains critical to understand, predict and enhance system reliability and performance using stochastic models, simulation and analytical methods. Experimental studies are also needed to parameterise, calibrate and validate models against real-world observations. These are precisely the themes of the MASCOTS conference series. We are very pleased that this yearÆs conference attracted 162 submissions fromall over the world, many of which were of the highest quality. Such a large number of submissions implied a correspondingly high reviewing load, and we are very grateful to the Programme Committee members and many external reviewers who provided between three and six reviews for each submission.\r\n\r\nBased on the critical reviews of the reviewers and discussions in the Programme Committee, we accepted 32 extended papers of the highest quality, 22 high-quality regular papers and 21 posters. The accepted submissions were from 25 countries spanning five continents, included submissions with industrial co-authors from 7 different companies, and covered a diverse set of research areas (e.g. workload modelling, load management and scheduling, performance optimisation and reliability/availability modeling), and diverse application contexts (e.g. parallel and multicore systems, wireless networks and storage systems). The conference programme has been organised broadly to reflect these themes and includes invited keynote tal

Conference paper

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