- Uncertain data
In
computer science , uncertain data is the notion of data that contains specificuncertainty . Uncertain data is typically found in the area ofsensor networks . When representing such data in adatabase , some indication of theprobability of the various values.There are three main models of uncertain data in databases. In attribute uncertainty, in each tuple, each uncertain attribute is subject to its own independent
probability distribution .cite journal|last=Prabhakar|first=Sunil |title=ORION: Managing Uncertain (Sensor) Data|url=http://mobisensors.cs.pitt.edu/files/papers/prabhakar.pdf] For example, if reading are taken of temperature and wind speed, each would be described by its own probability distribution, as knowing the reading for one measurement would not provide any information about the other.In correlated uncertainty, multiple attributes may be described by a
joint probability distribution . For example, if readings are taken of the position of an object, and the "x"- and "y"-coordinates stored, the probability of different values may depend on the distance from the recorded coordinates. As distance depends on both coordinates, it may be appropriate to use a joint distribution for these coordinates, as they are not independent.In tuple uncertainty, all the attributes of a tuple are subject to a joint probability distribution. This covers the case of correlated uncertainty, but also includes the case where there is a probability of a tuple not belonging in the relevant relation, which is indicates by all the probabilities not summing to one. For example, in a relation concerning female ducks, there may be uncertainty about the gender of a given duck.
Tuple uncertainty
Correlated uncertainty
References
*cite conference|first=Habich|later=Volk|coauthors=Clemens Utzny, Ralf Dittmann, Wolfgang Lehner|publisher=IEEE|accessdate=2008-08-01|title=Error-Aware Density-Based Clustering of Imprecise Measurement Values|booktitle=Seventh IEEE International Conference on Data Mining Workshops, 2007. ICDM Workshops 2007.
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