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IEEE Conference Publications
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Advanced traveler information systems (ATIS) deliver information derived from intelligent transportation systems data. ATIS continue to emerge and grow in popularity, as some of these systems are public and freely available. ATIS performance and perceived usefulness depends, among several design factors, on the reliability and quality of its data sources, especially when the systems are reporting current conditions. We present a sample scenario in which an inductive loop detector station along a freeway stops transmitting data, and an ATIS service presents an estimated state of the system instead of showing that no data is available. The estimation is based on sources of available and correlated data. Our first approach to implement an estimation framework consists of deriving a parametric description of the correlation from archived historical data. An example application is provided as well as suggestions for future research.
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The unbounded nature of data streams and the low-latency requirements of stream processing present interesting challenges in Data Stream Management System (DSMS) design. Streaming query operators are typically designed to produce results with low latency, as well as to efficiently manage their state. Stream-progress delimitation techniques, such as punctuation, can help query operators achieve these goals. In this work, we look at deriving execution guarantees with respect to result production and state management for complete queries over punctuated streams. These guarantees are derived before query execution. We formalize notions of successful stream processing at an operator level, and extend these definitions to stream queries as a whole. We introduce a framework, punctuation contracts, for analyzing data processing and punctuation propagation from input to output on individual operators. We then use our framework to analyze complete queries and determine, prior to execution, if every valid input is eventually emitted, and no item remains in operator state indefinitely. Finally, we discuss extensions needed to bound query memory requirements; we describe four stream properties that can be used to help understand and quantify memory and CPU usage.
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