Definition
A punctuation is an item embedded in a data stream that specifies a subset of the domain of that stream. A data item that belongs to the subset specified by a punctuation is said to match that punctuation. A data stream is said to be grammatical if, for each punctuation, no data items will follow that match that punctuation. Consider a stream of bids for online auctions. When an auction closes, a punctuation p is embedded in the stream that matches all bids for that auction. In a grammatical stream, p indicates no more bids will arrive from that stream for that auction.
In the most common format, a punctuation is a tuple of patterns, where each pattern corresponds to an attribute of the data items in a stream. Typically, four patterns are used: a wildcard (denoted by ‘*’) is matched by all values, a literal is matched by only the given value, a list (denoted by { }) is matched by any value in the given list, and a range(denoted by [ ]) is matched by any value that falls in...
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Li J, Maier D, Tufte K, Papadimos V, Tucker PA. Semantics and evaluation techniques for window aggregates in data streams. In: Proceedings of the ACM SIGMOD International Conference on Management of Data; 2005. p. 311–22.
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Maier, D., Tucker, P.A. (2018). Punctuations. In: Liu, L., Özsu, M.T. (eds) Encyclopedia of Database Systems. Springer, New York, NY. https://doi.org/10.1007/978-1-4614-8265-9_285
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