Bigtable is a distributed storage system for managing structured data that is designed to scale to a very large size: petabytes of data across thousands of commodity servers. Many projects at Google store data in Bigtable, including web indexing, Google Earth, and Google Finance. These applications

relevant to data stream systems and current projects in the area, the paper explores topics in stream query languages, new requirements and challenges in query processing, and algorithmic issues.

-group dependencies). We consider two natural semantics for dataflow constraints, namely, RTW (Real-Time Work-shop) semantics and LET (logical execution time) seman-tics. We show that while RTW semantics offers better end-to-end latency on the task group level, LET semantics al-lows tighter resource bounds

the necessary peak computation power in general-purpose systems. However, for a large class of applications in embedded real-time systems like cellular phones and camcorders, the variable operating frequency interferes with their deadline guarantee mechanisms, and DVS in this context, despite its growing

endto-end latencies and similar failure recovery properties. More importantly, it is able to achieve these results by using orders of magnitude lower control traffic. Finally, we present results from our wide-area testbed in which we experimented with 32-100 member groups distributed over 8 different

reviews the techniques used by such systems, and surveys current commercial and research systems. 1.

Emerald is an object-based language and system designed for the construction of distributed programs. An explicit goal of Emerald is support for object mobility; objects in Emerald can freely move within the system to take advantage of distribution and dynamically changing environments. We say

We consider the problem of routing traffic to optimize the performance of a congested network. We are given a network, a rate of traffic between each pair of nodes, and a latency function for each edge specifying the time needed to traverse the edge given its congestion; the objective is to route

that disconnected operation is feasible, efficient and usable by describing its design and implementation in the Coda File System. The central idea behind our work is that caching of data, now widely used for performance, can also be exploited to improve availability.

Bayou is a replicated, weakly consistent storage system designed for a mobile computing environment that includes portable machines with less than ideal network connectivity. To maximize availability, users can read and write any accessible replica. Bayou's design has focused on supporting