| Summary: | 碩士 === 國立清華大學 === 資訊系統與應用研究所 === 94 === A data stream is a real-time, continuous, and ordered sequence of data items. It is a widely used data format to deal with large amount of dynamic data. Dynamic content and unbounded storage requirement are the two main characteristics of data streams. We need to deal with these two issues while processing data streams. For the dynamic content issue, the approximate answering is a widely used approach to process queries on data streams. For the unbounded storage size issue, some data structures have been proposed to summarize the data streams and keep the storage space required small. Synopsis is a data structure that summarizes the data streams. By using some algorithms, users can get approximate answers of data streams from the summarized information stored in synopsis. In this thesis, we use the curve fitting technique to construct the synopsis of data streams in the form of a curve that expressed by a polynomial function. The algorithms for constructing the synopsis data structure and querying the data stream are also proposed. We prove that the storage space required by the proposed method is O(logN). From the experimental results, we observe that our approach can achieve 95% accuracy on data contents for the queries.
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