S - UWSpace - University of Waterloo

Chapter 1
Introduction
1.1 Data stream environment
1.1.1 Data streams
Traditional database management systems (DBMSs) are successful in many
real-world applications where data are modeled as persistent relations.
However, in the past decade, a set of applications has emerged that involve
processing large volumes of continuous data. The data involved
in these applications come in the form of streams. They are generated
continuously and in fixed order; the large volume (often assumed to be
unbounded) of the data that arrive in the stream makes it impossible to
store the entire stream on disk, and in many applications the data arrival
rate is high (e.g., hundreds or even thousands data per second). The
following are some typical examples of such applications:
• Sensor networks are becoming increasingly popular for environmental
and geophysical monitoring [10, 165], traffic monitoring [97], location
tracking [64], surveillance [162], and supply-chain analysis
[58]. The measurements produced by sensors can be modeled as a
continuous and unbounded stream of data.
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