CONCURRENCY AND COMPUTATION: PRACTICE AND EXPERIENCEConcurrency Computat.: Pract. Exper. 2009; 21:1419–1421Published online inWiley InterScience (www.interscience.wiley.com). DOI: 10.1002/cpe.1450

Guest Editorial: DistributedSimulation, VirtualEnvironments and Real-timeApplications

Welcome to this special issue of Concurrency and Computation on ‘Distributed Simulation, VirtualEnvironments and Real-time Applications’. The papers included in this special issue are basedmainly on selected extended versions of the best papers accepted in the 2007 International Sympo-sium on Distributed Simulation and Real Time Applications (DS-RT 2007). We have only acceptedfive papers in this special issue from many selected extended versions of papers accepted in DS-RT.This means that these accepted papers have undergone a thorough and a critical review process byexperts in the field.In their work Boukerche, Al Hamidi and Zhang described the design and implementation of a

web-based 3D virtual environment application that aims to help the training practice of personnelworking in the radiology department of a hospital. Their proposed system aims at helping users tolearn, to play or to be trained in a ‘like-real’ situation by using X3D technology and embedding itin a distributed virtual environment.Murray, Roberts, Steed, Sharkey, Dickerson, Rae and Wolff addressed an important issue related

to collaborative virtual environments and video conferencing. They are enhancing the 3D represen-tation of participants through avatars by mechanisms tracking people’s eyes and representing theirmovements on their avatars. Their approach is capable of reproducing the line of gaze as opposedto approximating it only. They also describe an experiment to assess the difference between users’abilities to judge what objects an avatar is looking at with only head movements being displayedand the eyes remaining static, and with eye gaze and head movement information being displayed.The results from the experiment showed that eye gaze is of vital importance to the subjects correctlyidentifying what a person is looking at in an immersive virtual environment.Hossain and El Saddik addressed several key issues in distributed multimedia services man-

agement and composition such as scalability, heterogeneity and QoS. Their proposed frameworkintroduced biologically inspired multimedia service management through the composition of differ-ent multimedia services such as streaming and transcoding services. They make use of biologicallyinspired algorithms in order to collect the QoS requirements from individual transcoding servicesthat fulfill the requirements of the composition process. A prototype of the proposed framework isdesigned, implemented and evaluated in terms of scalability and load balancing.Lees, Logan and Theodoropoulos described an optimistic synchronisation algorithm for parallel

discrete event simulation of multi-agent systems, and showed that it outperforms Time Warp and

Copyright © 2009 John Wiley & Sons, Ltd.

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time windows on a range of test cases. Their proposed DTRD algorithm uses a decision theoreticmodel of rollback to derive an optimal time to delay read event so as to maximize the rate of LVTprogression. Their analysis suggests that the performance of the algorithm is relatively insensitiveto events whose inter-arrival times are not normally distributed.Chetlur and Wilsey described a distributed cancellation mechanism using Total Clocks to prevent

cascading and inter-related rollbacks in distributed simulations. The scalability of total clocksis addressed through a time-stamp mechanism referred as plausible total clocks and a proactivecancellation mechanism. They showed that the size of plausible total clocks is dependent on thenumber of LPs (n) and independent of the number of simulation objects (m) (typically n � m). Aproof of correctness of the cancellation mechanism using plausible total clocks is then presentedto show that only erroneous computations will be annihilated by this technique. Scalability of thistechnique to track causal relationship makes it suitable for a practical implementation.Mustafee and Taylor introduced WinGrid, a desktop grid computing middleware, specifically

designed for executing CSP-based simulations on Windows computers. The authors discussed theuse of WinGrid in support of FIRST, a specialist simulation application using the CSP Witness,and the IRS-RBF simulation, a credit risk simulation application using the CSP Analytics. AGrid-enabled version of FIRST and the IRS-RBF simulation has been developed with minimumtechnological intervention. The performance results of the grid-enabled version of FIRST and theIRS-RBF simulation were presented and discussed in detail. Their work tries to focus attention onthe benefit that small desktop grids can give to simulation in industry in the future.

ACKNOWLEDGEMENTS

I would like to thank all the authors and reviewers for their contributions and devoted efforts. A special thankyou goes to the technical program committee of DS-RT for their valuable time and superior work. Thanks arealso due to the editorial assistants for their fine support.

Finally, special thanks to the Editors-in-Chiefs of Concurrency and Practice for hosting this special issue. Ihope that the work reported here will motivate further research and development efforts in this intriguing andvital technology.

Guest EditorsAbdulmotaleb El Saddik is the University research chair and professor, SITE, University ofOttawa and recipient of the Professional of the Year Award (2008), the Friedrich Wilhelm-BesselResearch Award from Germany’s Alexander von Humboldt Foundation (2007), the Premier’sResearch Excellence Award (PREA 2004) and the National Capital Institute of Telecommunications(NCIT) New Professorship Incentive Award (2004). He is the director of the Multimedia Commu-nications Research Laboratory (MCRLab). He is a Theme co-Leader in the LORNET NSERCResearch Network. He is associate editor of the ACM Transactions on Multimedia Computing,Communications and Applications (ACM TOMCCAP), IEEE Transactions on Multimedia (TMM)and IEEE Transactions on Computational Intelligence and AI in Games (IEEE TCIAIG) and guesteditor for several IEEE Transactions and Journals. Dr El Saddik has been serving on several techni-cal program committees of numerous IEEE and ACM events. He has been the general chair and/ortechnical program chair of more than 20 international conferences symposia and workshops oncollaborative hapto-audio-visual environments, multimedia communications and instrumentation

Copyright q 2009 John Wiley & Sons, Ltd. Concurrency Computat.: Pract. Exper. 2009; 21:1419–1421DOI: 10.1002/cpe

EDITORIAL 1421

and measurement. He was the general co-chair of ACM MM 2008. He is a leading researcher inhaptics, service-oriented architectures, collaborative environments and ambient interactive mediaand communications. He has authored and co-authored two books and more than 250 publications.He has received research grants and contracts totaling more than $10 million and has supervisedmore than 90 researchers. His research has been selected for the BEST Paper Award three times.Dr El Saddik is a senior member of ACM, an IEEE distinguished lecturer and a fellow of IEEE.

Mirela Sechi Moretti Annoni Notare is a professor and vice-president of the Superior Council atBarddal University, Brasil. She received her MSc and PhD degrees from the Federal University ofSanta Catarina (UFSC) and a BSc degree from Passo Fundo University—all the three degrees inComputer Science.Her main research of interest focuses on the proposition of security management solutions for

wireless, mobile, sensor and Ad Hoc networks. Dr Mirela Notare has published widely in theseareas. She also received several awards and citations, such as National Award for TelecommunicationSoftware, Tv Globo.She served as general co-chair for the IEEE I2TS (International Information and Telecommu-

nication Technologies Symposium) and program co-chair for the IEEE MobiWac (Mobility andWireless Access Workshop) and IEEE International Workshop on Performance and Managementof Wireless and Mobile Networks and the 2nd ACM International Workshop on QoS and Securityfor Wireless and Mobile Networks. She has been serving as a program committee member in sev-eral scientific IEEE and ACM conferences, including ACM MSWiM, IEEE/ACM ANSS, IEEEICC, IEEE IPDPS/WMAN, IEEE Globecom/AdHoc, Sensor and Mesh Networking Symposiu,and IEEE/SBC SSI.She has been guest editor for several international journals, such as JOIN (The International

Journal of Interconnection Netwroks), IJWMC (Journal of Wireless and Mobile Computing), JBCS(Journal of Brazilian Computer Society), Elsevier JPDC (The International Journal of Parallel andDistributed Computing), Wiley & Sons Journal of Wireless Communications &Mobile Computing,and Wiley Concurrency and Com putation Journal. She has wildely published her work in highlyregarded journals such as JPDC among others. She is the author of a book on Protocol Engineeringwith LOTOS/ISO (UFSC). She is the current editor-in-chief of IEEE Latin America Transactions.She is the founder and president of STS Co, a senior member of IEEE and member of SBrT and

SBC societies.

ABDULMOTALEB EL SADDIK

University of Ottawa

MIRELA SECHI MORETTI ANNONI NOTARE

Barddal University

Copyright q 2009 John Wiley & Sons, Ltd. Concurrency Computat.: Pract. Exper. 2009; 21:1419–1421DOI: 10.1002/cpe