March – 2006 ^April

Web enabled application servers and the clients for their Web services have increased in both the sophistication of server capabilities as well as in the demand for client customization. Therefore, there is a necessity of a specification language for sophisticated client needs and a framework for resource monitoring and data delivery that goes beyond existing standards. After presenting the current state-of-affair in Web resource monitoring, the talk will focus on efficient scheduling algorithms for monitoring an information source whose contents change at times modeled by a nonhomogeneous Poisson process. In a given time period of length T, we enforce a server-side politeness constraint that we may only probe the source at most n times. This constraint, along with an optional constraint that no two probes may be spaced less than delta time units apart, is intended to prevent the monitor from being classified as a nuisance to be "locked out" of the information source.

This work is a joint work with Jonathan Eckstein and Sarit Reiner

Bio: Avigdor Gal is a faculty member at the Faculty of Industrial Engineering & Management at the Technion. He received his D.Sc. degree from the Technion-Israel Institute of Technology in 1995 in the area of temporal active databases. During his studies, Avigdor has received the Miriam and Aaron Gutwirth Scholarship three years in a row (1993-1995). He has published more than 50 papers in journals (e.g. Journal of the ACM and IEEE Transactions on Knowledge and Data Engineering), books (Temporal Databases: Research and Practice) and conferences (e.g. CoopIS'98 - best paper award-, ER'2005, CoopIS'2005, BPM'2005) on the topics of information systems architectures, active databases and temporal databases. Avigdor is a three time recepient of the IBM Academic Fellow Award. He was an Associate Editor of SIGMOD Record and is a member of the CoopIS Advisory Board.

Multi-camera systems are an emerging class of systems with unique features. The correspondence problem is a fundamental component in solutions to many problems in multi-camera systems including calibration, object recognition, 3D scene reconstruction, and tracking. Existing vision applications in a multi-camera setting are typically based on a central computer that gathers the information from all cameras, and performs the necessary computations. Such use of a central server has a number of distinct disadvantages. One is the problem of scalability of the computational task as the number of cameras grows. Another is that the server can become a communication hot-spot and possible bottleneck. Finally, the central server is a single point of failure. The disadvantages of the central server motivate distributed solutions that are not based on a central server. In this case, reasonably powerful processors that are attached to the cameras communicate among themselves and perform all necessary computations. This scenario is quite realistic, which further motivates the distributed approach.

In this talk I will present a probabilistic algorithm for finding correspondences across multiple images. The algorithm employs the theory of random graphs to provide an efficient probabilistic algorithm that performs Wide-based Stereo (WBS) comparisons on a small number of image pairs, and then propagates correspondence information among the cameras. The method is robust to communication and processors failures, and to failures of the WBS computation. Our method can be extended to handle other distributed tasks that involve computing equivalence relation between large sets of processors

This is a joint work with: Yoram Moses, Technion Israel, Shai Avidan, IDC Israel.

In this talk I will survey the latest development in dynamic algorithms for fundamental graph problems, such as shortest paths, reachability and connectivity. In the last five years there were many STOC/FOCS/SODA publications on dynamic graphs. I will overview the most important results in the area and will focus on two results regarding shortest paths which are part of my PhD thesis.