Sirish Chandrasekaran

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Increasingly pervasive networks are leading towards a world where data is constantly in motion. In such a world, conventional techniques for query processing, which were developed under the assumption of a far more static and predictable computational environment, will not be sufficient. Instead, query processors based on adaptive dataflow will be(More)
The long-running nature of continuous queries poses new scalability challenges for dataflow processing. CQ systems execute pipelined dataflows that may be shared across multiple queries. The scalability of these dataflows is limited by their constituent, stateful operators – e.g. windowed joins or grouping operators. To scale such operators, a natural(More)
At Berkeley, we are developing TelegraphCQ [1, 2], a dataflow system for processing continuous queries over data streams. TelegraphCQ is based on a novel, highly-adaptive architecture supporting dynamic query workloads in volatile data streaming environments. In this demonstration we show our current version of TelegraphCQ, which we implemented by(More)
This paper studies Data Stream Management Systems that combine real-time data streams with historical data, and hence access incoming streams and archived data simultaneously. A significant problem for these systems is the I/O cost of fetching historical data which inhibits processing of the live data streams. Our solution is to reduce the I/O cost for(More)
As query engines are scaled and federated, they must cope with highly unpredictable and changeable environments. In the Telegraph project, we are attempting to architect and implement a continuously adaptive query engine suitable for global-area systems, massive parallelism, and sensor networks. To set the stage for our research, we present a survey of(More)
We are building TelegraphCQ, a system to process continuous queries over data streams. Although we had implemented some parts of this technology in earlier Java-based prototypes, our experiences were not positive. As a result, we decided to use PostgreSQL, an open source RDBMS as a starting point for our new implementation. In March 2003, we completed an(More)
Recent work on querying data streams has focused on systems where newly arriving data is processed and continuously streamed to the user in real time. In many emerging applications, however, ad hoc queries and/or intermittent connectivity also require the processing of data that arrives prior to query submission or during a period of disconnection. For such(More)
Building highly available enterprise applications using web-oriented middleware is hard. Runtime implementations frequently do not address the problems of application state persistence and fault-tolerance, placing the burden of managing session state and, in particular, handling system failures on application programmers. This paper describes Phoenix/APP, a(More)
Nasopharyngeal carcinoma has been reported to have a higher incidence of distant metastases as compared to other head and neck cancers. Distant metastases of nasopharyngeal carcinoma has been reported in the bones, lungs, liver, distant lymph nodes, brain and porta hepatis. This report presents a case of nasopharyngeal carcinoma with secondaries in the(More)