Browsing by Author "LEE, Mong-Li"
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- ItemA Stratified Approach to Progressive Approximate Joins(2007-09-24) TOK, Wee Hyong; BRESSAN, Stéphane; LEE, Mong-LiUsers often do not require a complete answer to their query but rather only a sample. They expect the sample to be either the largest possible or the most representative (or both) given the resources available. We call the query processing techniques that deliver such results approximate. Process- ing of queries to streams of data is said to be progressive when it can continuously produce results as data arrives. In this paper, we are interested in the progressive and approxi- mate processing of queries to data streams when processing is limited to main memory. In particular, we study one of the main building blocks of such processing: the progressive approximate join. We devise and present several novel progressive approximate join algorithms. We empirically evaluate the performance of our algorithms and compare them with those of algorithms based on existing techniques. In particu- lar we study the trade-off between maximization throughput and maximization of representativeness of the sample.
- ItemTwig'n Join: Progressive Query Processing of Multiple XML Streams(2007-09-03T08:58:02Z) TOK, Wee Hyong; BRESSAN, Stephane; LEE, Mong-LiWe propose a practical approach to the progressive processing of (FWR) XQuery queries on multiple XML streams, called Twig.n Join (or TnJ). The query is decomposed into a query plan combining several Twig queries on the individual streams, followed by a join and a final Twig query. The processing is itself accordingly decomposed into three pipelined stages progressively producing streams of XML fragments. We use the recently proposed TwigM algorithm for the progressive evaluation of Twig queries. We devise an original progressive join algorithm for the XML fragments leveraging our previous work on relational result-rate based progressive joins. In addition, we propose a multi-way XML value join algorithm, which uses a result-oriented approach to determine the probing sequence for multiple XML streams. We comparatively evaluate the performance of the Twig.n Join variants using both synthetic and real-life data from standard XML query processing benchmarks. We show that Twig.n Join with a result-rate based approach is most effective and efficient.