In this work, we present an architecture for interactive distributed multimedia information servi... more In this work, we present an architecture for interactive distributed multimedia information services. The service consists of three basic parts, the clients, the access servers, and the content servers. Clients manage the presentation of the requested multimedia documents, while also ensure the synchronization among various involved media. Special policies for the synchronized presentation of multimedia documents and user interactions management are discussed. Access servers authorize the users for legitimate use of the service, while also provide various searching capabilities Content servers manage the transportation of multimedia documents over a broadband network and the user interactions. The proposed architecture preserves scalability, flexibility and modularity due to the distributed nature of the architecture, while also results in good performance due to the dynamic allocation of resources.
Stackelberg games [15] may model the interplay among an authority and rational individuals that s... more Stackelberg games [15] may model the interplay among an authority and rational individuals that selfishly demand resources on a large-scale network. In such a game, the authority (Leader) of the network is modeled by a distinguished player. The selfish users (Followers) are modeled by the remaining players. It is well known that selfish behavior may yield a Nash Equilibrium with cost arbitrarily higher than the optimum one, yielding unbounded Coordination Ratio or Price of Anarchy (PoA) [7, 13]. Leader plays his strategy first assigning a portion of the total demand to some resources of the network. Followers observe and react selfishly assigning their demand to the most appealing resources. Leader aims to drive the system to an a posteriori Nash equilibrium with cost close to the overall optimum one [4, 6, 8, 10]. Leader may also be eager for his own rather than system’s performance [2, 3]. A Stackelberg game can be seen as a special, and easy [6] to implement, case of Mechanism Design. It avoids the complexities of either computing taxes or assigning prices, or even designing the network at hand [9]. However, a central authority capable to control the overall demand on the resources of a network may be unrealistic in networks which evolute and operate under the effect of many and diversing economic entities. A realistic way [4] to act centrally even in large nets could be via Virtual Private Networks (VPNs) [1]. Another flexible way is to combine such strategies with Tolls [5, 14]. A dictator controlling the entire demand optimally on the resources surely yields PoA = 1. On the other hand, rational users do prefer a liberal world to live. Thus, it is important to compute the optimal Leader strategy which controls the minimum of the resources (Price of Optimum) and yields PoA D 1. What is the complexity of computing the Price of Optimum? This is not trivial to answer, since the Price of Optimum depends crucially on computing an optimal Leader strategy. In particular, [6] proved that computing the optimal Leader strategy is hard.
In this paper we present a software tool for the realisation of the distance education service, t... more In this paper we present a software tool for the realisation of the distance education service, that is the conduction of classes through the use of computers. The classes are directed towards personnel in various areas and aim at the retraining and update of the personnel in subjects of special interest in their line of work. The conduction of classes takes place, from and towards, remote regions with the aid of a computer network. Hippocrates is a flexible and easy-to-use application, which permits students, who sit in front of remotely situated workstations, to attend classes or seminars given by a teacher or expert, who can also be located in some remote geographical area. Hippocrates can be thought of as a distributed transparency projector. The teacher can project transparencies on the screens of the students' workstations and can emphasize or indicate regions of interest on them by using the graphical tools offered by Hippocrates. Immediate results of the use of Hippocrates are the fast updating of the personnel in remote areas and the upgrading of the quality of the services they offer.
Proceedings of 5th IEEE International Symposium on High Performance Distributed Computing HPDC-96, 1996
In this paper we present a uni ed approach for delivering hypermedia/multimedia objects over broa... more In this paper we present a uni ed approach for delivering hypermedia/multimedia objects over broadband networks. Documents are s t o r ed in various multimedia servers, while the inline data may reside in their own media servers, attached to the multimedia servers. The described service c onsists of several multimedia servers and a set of functions that intend to present to the end user interactive information in real-time. Users interact with the service r equesting multimedia documents on demand. Various media streams are t r ansmitted over di erent parallel connections according to their transmission requirements. The hypermedia documents are structured using a hypermedia markup language that keeps information of the spatiotemporal relationships among document's media components. In order to deal with the variant network behavior, bu ering manipulation mechanisms and grading of the transmitted m e dia quality techniques are p r oposed t o smooth presentation and synchronization anomalies.
We present here a high performance parallel free-text retrieval m ethod for multiple text queries... more We present here a high performance parallel free-text retrieval m ethod for multiple text queries using the vector space model. Our method employs the fat-tree area universal routing network for connecting the processors of the parallel m achine. We provide a theoretical analysis of our technique which shows it t o b e superior to parallel t ext retrieval based
Proceedings 15th International Parallel and Distributed Processing Symposium. IPDPS 2001
Mobile computing has emerged as an important area of computing today as we move to the next mille... more Mobile computing has emerged as an important area of computing today as we move to the next millennium. This has been made possible due to the tremendous and continued growth of wireless communications and network technology over the past decade, providing infrastructures for "anytime anywhere" access to distributed computing systems and information repositories. The mobility of users offers new challenges to seamless connectivity in a distributed, heterogeneous network of wireline and wireless components. Several techniques and algorithms developed by the parallel and distributed computing community can be applied to solve typical wireless networks and mobile computing: routing, scheduling, load balancing, cache coherence, information access, and QoS provisioning problems. The objective of this workshop is to bring together technologists and researchers of international reputation in the areas of Parallel and Distributed Computing and Wireless Networks and Mobile Computing in order to have a forum for discussions, exchange of ideas and presentations. It is indeed a very appropriate to have this workshop as part of the IPDPS activities. We received twenty eight papers for the workshop. Each paper was sent to three program committee members for reviewing and after the review process we selected fourteen papers for presentation at the workshop. Due to the high quality of papers received, we had to reject some good papers. We take this opportunity to thank authors of all submitted papers and the referees for their efforts in making this workshop a success. Special thanks to all the steering committee members, the general chair, the publicity chairs and the technical program committee members for their support and assistance. We look forward to having a very fruitful and enjoyable workshop.
... 5. H. Chan, A. Perrig, and D. Song, “Random Key Predistribution Schemes for Sensor Networks”,... more ... 5. H. Chan, A. Perrig, and D. Song, “Random Key Predistribution Schemes for Sensor Networks”, Proceedings of the IEEE Symposium of Privacy and Security”, 11–14 May, pp. 197–213, 2003. 6. A. CF. Chan and ES Rogers ...
In a number of situations, it is necessary for two agents who may have never communicated in the ... more In a number of situations, it is necessary for two agents who may have never communicated in the past to, jointly, create a shared information item which can serve as a basis for subsequent protocols that the agents may wish to execute (e.g., negotiation or encryption protocols). One way to create this shared piece of information is to have the two agents start with one random bit string each and then engage in a protocol that enables them to transform, gradually, bit differences (in their strings) into bit agreements. In a previous work, an efficient protocol was proposed which was based on the use of the Extended Golay error-correcting code in order to locate and “correct” bit differences. In this work we generalize this protocol in order to use any generic error-correcting code and derive theoretical performance bounds on the efficiency, based on the characteristics of the employed code. The proposed generalized protocol is fair, in that the final strings (which have the same bits in the majority of positions) depend on the strings possessed by both agents while each agent contributes to the same degree in the formation of these strings. Finally, the proposed protocol is lightweight (both computationally and with respect to message exchanges) and, thus, can be implemented in embedded systems and resource limited devices.
ABSTRACT In this paper, we propose simple protocols for enabling two communicating agents that ma... more ABSTRACT In this paper, we propose simple protocols for enabling two communicating agents that may have never met before to extract common knowledge out of any initial knowledge that each of them possesses. The initial knowledge from which the agents start, may even be independent of each other, implying that the two agents need not have had previous access to common information sources. In addition, the common knowledge extracted upon the termination of the protocols depends, in a fair way, on the (possibly independent) information items initially known, separately, by the two agents. It is fair in the sense that there is a negotiation between the two agents instead of one agent forcing the other to conform to its own knowledge. These protocols, may be extended in order to support security applications where the establishment of a common knowledge is required. Moreover, the implementation of the protocols leads to reasonably small code that can also fit within resource limited devices involved in any communication network while, at the same time, it is efficient as simulation results demonstrate.
A classical problem in scheduling theory is to find an optimal nonpreem-tive sched~e for a collec... more A classical problem in scheduling theory is to find an optimal nonpreem-tive sched~e for a collection of unit length tasks subject to precedence con-straints. We are given n tasks to be executed on m processors. Each task requires exactly one unit of execution and can run on any ...
In this work, we present an architecture for interactive distributed multimedia information servi... more In this work, we present an architecture for interactive distributed multimedia information services. The service consists of three basic parts, the clients, the access servers, and the content servers. Clients manage the presentation of the requested multimedia documents, while also ensure the synchronization among various involved media. Special policies for the synchronized presentation of multimedia documents and user interactions management are discussed. Access servers authorize the users for legitimate use of the service, while also provide various searching capabilities Content servers manage the transportation of multimedia documents over a broadband network and the user interactions. The proposed architecture preserves scalability, flexibility and modularity due to the distributed nature of the architecture, while also results in good performance due to the dynamic allocation of resources.
Stackelberg games [15] may model the interplay among an authority and rational individuals that s... more Stackelberg games [15] may model the interplay among an authority and rational individuals that selfishly demand resources on a large-scale network. In such a game, the authority (Leader) of the network is modeled by a distinguished player. The selfish users (Followers) are modeled by the remaining players. It is well known that selfish behavior may yield a Nash Equilibrium with cost arbitrarily higher than the optimum one, yielding unbounded Coordination Ratio or Price of Anarchy (PoA) [7, 13]. Leader plays his strategy first assigning a portion of the total demand to some resources of the network. Followers observe and react selfishly assigning their demand to the most appealing resources. Leader aims to drive the system to an a posteriori Nash equilibrium with cost close to the overall optimum one [4, 6, 8, 10]. Leader may also be eager for his own rather than system’s performance [2, 3]. A Stackelberg game can be seen as a special, and easy [6] to implement, case of Mechanism Design. It avoids the complexities of either computing taxes or assigning prices, or even designing the network at hand [9]. However, a central authority capable to control the overall demand on the resources of a network may be unrealistic in networks which evolute and operate under the effect of many and diversing economic entities. A realistic way [4] to act centrally even in large nets could be via Virtual Private Networks (VPNs) [1]. Another flexible way is to combine such strategies with Tolls [5, 14]. A dictator controlling the entire demand optimally on the resources surely yields PoA = 1. On the other hand, rational users do prefer a liberal world to live. Thus, it is important to compute the optimal Leader strategy which controls the minimum of the resources (Price of Optimum) and yields PoA D 1. What is the complexity of computing the Price of Optimum? This is not trivial to answer, since the Price of Optimum depends crucially on computing an optimal Leader strategy. In particular, [6] proved that computing the optimal Leader strategy is hard.
In this paper we present a software tool for the realisation of the distance education service, t... more In this paper we present a software tool for the realisation of the distance education service, that is the conduction of classes through the use of computers. The classes are directed towards personnel in various areas and aim at the retraining and update of the personnel in subjects of special interest in their line of work. The conduction of classes takes place, from and towards, remote regions with the aid of a computer network. Hippocrates is a flexible and easy-to-use application, which permits students, who sit in front of remotely situated workstations, to attend classes or seminars given by a teacher or expert, who can also be located in some remote geographical area. Hippocrates can be thought of as a distributed transparency projector. The teacher can project transparencies on the screens of the students' workstations and can emphasize or indicate regions of interest on them by using the graphical tools offered by Hippocrates. Immediate results of the use of Hippocrates are the fast updating of the personnel in remote areas and the upgrading of the quality of the services they offer.
Proceedings of 5th IEEE International Symposium on High Performance Distributed Computing HPDC-96, 1996
In this paper we present a uni ed approach for delivering hypermedia/multimedia objects over broa... more In this paper we present a uni ed approach for delivering hypermedia/multimedia objects over broadband networks. Documents are s t o r ed in various multimedia servers, while the inline data may reside in their own media servers, attached to the multimedia servers. The described service c onsists of several multimedia servers and a set of functions that intend to present to the end user interactive information in real-time. Users interact with the service r equesting multimedia documents on demand. Various media streams are t r ansmitted over di erent parallel connections according to their transmission requirements. The hypermedia documents are structured using a hypermedia markup language that keeps information of the spatiotemporal relationships among document's media components. In order to deal with the variant network behavior, bu ering manipulation mechanisms and grading of the transmitted m e dia quality techniques are p r oposed t o smooth presentation and synchronization anomalies.
We present here a high performance parallel free-text retrieval m ethod for multiple text queries... more We present here a high performance parallel free-text retrieval m ethod for multiple text queries using the vector space model. Our method employs the fat-tree area universal routing network for connecting the processors of the parallel m achine. We provide a theoretical analysis of our technique which shows it t o b e superior to parallel t ext retrieval based
Proceedings 15th International Parallel and Distributed Processing Symposium. IPDPS 2001
Mobile computing has emerged as an important area of computing today as we move to the next mille... more Mobile computing has emerged as an important area of computing today as we move to the next millennium. This has been made possible due to the tremendous and continued growth of wireless communications and network technology over the past decade, providing infrastructures for "anytime anywhere" access to distributed computing systems and information repositories. The mobility of users offers new challenges to seamless connectivity in a distributed, heterogeneous network of wireline and wireless components. Several techniques and algorithms developed by the parallel and distributed computing community can be applied to solve typical wireless networks and mobile computing: routing, scheduling, load balancing, cache coherence, information access, and QoS provisioning problems. The objective of this workshop is to bring together technologists and researchers of international reputation in the areas of Parallel and Distributed Computing and Wireless Networks and Mobile Computing in order to have a forum for discussions, exchange of ideas and presentations. It is indeed a very appropriate to have this workshop as part of the IPDPS activities. We received twenty eight papers for the workshop. Each paper was sent to three program committee members for reviewing and after the review process we selected fourteen papers for presentation at the workshop. Due to the high quality of papers received, we had to reject some good papers. We take this opportunity to thank authors of all submitted papers and the referees for their efforts in making this workshop a success. Special thanks to all the steering committee members, the general chair, the publicity chairs and the technical program committee members for their support and assistance. We look forward to having a very fruitful and enjoyable workshop.
... 5. H. Chan, A. Perrig, and D. Song, “Random Key Predistribution Schemes for Sensor Networks”,... more ... 5. H. Chan, A. Perrig, and D. Song, “Random Key Predistribution Schemes for Sensor Networks”, Proceedings of the IEEE Symposium of Privacy and Security”, 11–14 May, pp. 197–213, 2003. 6. A. CF. Chan and ES Rogers ...
In a number of situations, it is necessary for two agents who may have never communicated in the ... more In a number of situations, it is necessary for two agents who may have never communicated in the past to, jointly, create a shared information item which can serve as a basis for subsequent protocols that the agents may wish to execute (e.g., negotiation or encryption protocols). One way to create this shared piece of information is to have the two agents start with one random bit string each and then engage in a protocol that enables them to transform, gradually, bit differences (in their strings) into bit agreements. In a previous work, an efficient protocol was proposed which was based on the use of the Extended Golay error-correcting code in order to locate and “correct” bit differences. In this work we generalize this protocol in order to use any generic error-correcting code and derive theoretical performance bounds on the efficiency, based on the characteristics of the employed code. The proposed generalized protocol is fair, in that the final strings (which have the same bits in the majority of positions) depend on the strings possessed by both agents while each agent contributes to the same degree in the formation of these strings. Finally, the proposed protocol is lightweight (both computationally and with respect to message exchanges) and, thus, can be implemented in embedded systems and resource limited devices.
ABSTRACT In this paper, we propose simple protocols for enabling two communicating agents that ma... more ABSTRACT In this paper, we propose simple protocols for enabling two communicating agents that may have never met before to extract common knowledge out of any initial knowledge that each of them possesses. The initial knowledge from which the agents start, may even be independent of each other, implying that the two agents need not have had previous access to common information sources. In addition, the common knowledge extracted upon the termination of the protocols depends, in a fair way, on the (possibly independent) information items initially known, separately, by the two agents. It is fair in the sense that there is a negotiation between the two agents instead of one agent forcing the other to conform to its own knowledge. These protocols, may be extended in order to support security applications where the establishment of a common knowledge is required. Moreover, the implementation of the protocols leads to reasonably small code that can also fit within resource limited devices involved in any communication network while, at the same time, it is efficient as simulation results demonstrate.
A classical problem in scheduling theory is to find an optimal nonpreem-tive sched~e for a collec... more A classical problem in scheduling theory is to find an optimal nonpreem-tive sched~e for a collection of unit length tasks subject to precedence con-straints. We are given n tasks to be executed on m processors. Each task requires exactly one unit of execution and can run on any ...
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