11997775
XML Query Routing in Structured P2P Systems
This paper addresses the problem of data placement, indexing, and querying large XML data repositories distributed over an existing P2P service infrastructure. Our architecture scales gracefully to the network and data sizes, is fully distributed, fault tolerant and self-organizing, and handles complex queries efficiently, even those queries that use full-text search. Our framework for indexing distributed XML data is based on both meta-data information and textual content. We introduce a novel data synopsis structure to summarize text that correlates textual with positional information and increases query routing precision. Our processing framework maps an XML query with full-text search into a distributed program that migrates from peer to peer, collecting relevant document locations along the way. In addition, we introduce methods to handle network updates, such as node arrivals, departures, and failures. Finally, we report on a prototype implementation, which is used to validate the accuracy of our data synopses and to analyze the various costs involved in indexing XML data and answering queries.
6061688
Mobile Agent Connection Establishment and Management (CEMA)—Message Exchange for Pervasive Computing Environments
Pervasive computing is an emerging technology that offers new possibilities to distributed computing and computer networking; it employs a wide variety of smart, ubiquitous devices throughout an individual's working and living environment. Mobile agents are software entities that can migrate between servers (mobile agent environments) of the network accomplishing various tasks on the behalf of their owners. The objective of this paper is to describe a test and prototyping environment for experimenting with mobile agents in pervasive environments. A prototype environment for a novel, proactive infrastructure is described for mobile agent assisted pervasive computing. In addition, a new message passing algorithm is provided for mobile agent connection establishment and management (CEMA). Simulation results show the performance of the proposed approach.
29185449
Performance Analysis and Scalability of the ThreadmanTM Thread Manager
6748545
Quality of Service Primitives for Operating System Support of Multimedia Applications
11624555
A Query Algebra for Fragmented XML Stream Data
The increased usage of mobile devices coupled with an unprecedented demand for information has pushed the scalability problem of pull-based data service to the focus. A broadcast model of streaming data over a wireless medium has been proposed as a viable alternative for information dissemination. In the streaming broadcast model, servers broadcast data in an asynchronous and unacknowledged mode while clients process personalized and complex queries locally, relieving the load on the server. We address the query processing of streamed XML data, which is fragmented into manageable chunks for easier synchronization. Although there has been some work done in defining algebras that model XQueries on XML documents, no work has been done in defining query algebras for fragmented XML stream data. We define a model for processing fragmented XML stream data, using the concept of holes and fillers. This model offers the flexibility required by the server to disseminate data in manageable fragments, whenever they become available, and to send repetitions, replacements and removal of fragments. We then present a query algebra for XQuery that operates on this streamed XML data model. The XML fragments are operated upon in a continuous pipelined fashion without the need of materializing the transmitted document at the client site.
10614369
PICO: A Middleware Framework for Pervasive Computing
The pervasive information community organization is a framework for creating mission-oriented dynamic communities of autonomous software entities that perform tasks for users and devices. PICO's telemedicine example scenario demonstrates its potential as a simple, unique, and versatile middleware framework for pervasive computing.
24464091
Contours of constructive hypertexts
Discussion of hypertext rhetoric and criticism has foeused on small, freed hypertext that am typically used by casual readers for comparatively short periods. Here we explo~ complex, constructive hypertext, intended to inform and to infIuence dedicated and thoughtful readers. Recurrence and multivalence, both deplored in small hypertext, prove from study of mom complex texts to be very valuable. While static, graph-theoretic measures facilitate understanding of Ioeal hypertext structure, the structures of meaning or contours we observe in current hypertext fiction and scholarship do not appear to reside in static structures, but rather in the complex and dynamic perceptions of the engagedreader.
6198667
CABOB: A Fast Optimal Algorithm for Combinatorial Auctions
Combinatorial auctions where bidders can bid on bundles of items can lead to more economical allocations, but determining the winners is NP-complete and inapproximable. We present CABOB, a sophisticated search algorithm for the problem. It uses decomposition techniques, upper and lower bounding (also across components), elaborate and dynamically chosen bid ordering heuristics, and a host of structural observations. Experiments against CPLEX 7.0 show that CABOB is usually faster, never drastically slower, and in many cases drastically faster. We also uncover interesting aspects of the problem itself. First, the problems with short bids that were hard for the first-generation of specialized algorithms are easy. Second, almost all of the CATS distributions are easy, and become easier with more bids. Third, we test a number of random restart strategies, and show that they do not help on this problem because the run-time distribution does not have a heavy tail (at least not for CABOB).
15239156
Application of a hybrid genetic algorithm to airline crew scheduling
This paper discusses the development and application of a hybrid genetic algorithm to airline crew scheduling problems. The hybrid algorithm consists of a steady-state genetic algorithm and a local search heuristic. The hybrid algorithm was tested on a set of 40 real-world problems. It found the optimal solution for half the problems, and good solutions for 9 others. The results were compared to those obtained with branch-and-cut and branch-and-bound algorithms. The branch-and-cut algorithm was significantly more successful than the hybrid algorithm, and the branch-and-bound algorithm slightly better.
29157947
Massively parallel computation of conservation laws
Abstract We present a new method for computing solutions of conservation laws based on the use of cellular automata with the method of characteristics. The method exploits the high degree of parallelism available with cellular automata and retains important features of the method of characteristics. It yields high numerical accuracy and extends naturally to adaptive meshes and domain decomposition methods for perturbed conservation laws. We describe the method and its implementation for a Dirichlet problem with a single conservation law for the one-dimensional case. Numerical results for the one-dimensional law with the classical Burgers nonlinearity or the Buckley-Leverett equation show good numerical accuracy outside the neighborhood of the shocks. The error in the area of the shocks is of the order of the mesh size. The algorithm is well suited for execution on both massively parallel computers and vector machines. We present timing results for an Alliant FX/8, Connection Machine Model 2, and CRAY X-MP.
20665084
Parallel performance of two applications in the Boeing high performance computing benchmark suite
Abstract We describe our work to evaluate the performance of the parallel versions of two floating-point-intensive engineering applications from Boeing's high performance computing benchmark suite (BHPCBS) on emerging RISC parallel systems and PC clusters. The first application is a computational fluid dynamics (CFD) code, OVERFLOW, developed by NASA and used by Boeing for analysis and design of advanced aircraft. The second application is a prototype of a computational electromagnetics (CEM) code, developed by Boeing and used for radar cross-section studies. The distributed memory parallel versions of both applications use the message passing interface (MPI) standard for message passing. The goal of our work was to determine whether RISC parallel systems and PC clusters, which offer high performance at low cost, may be able to meet Boeing's computing requirements in the future. We describe the test environments for the studies, discuss parallelization issues and strategies and present performance data for the two applications.