NOTICE: The project that is the subject of this report was approved by the Governing Board of the National Research Council, whose members are drawn from the councils of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine. The members of the committee responsible for the report were chosen for their special competences and with regard for appropriate balance.

This study was supported by the National Security Agency (Grant #MDA904–02–1–0114), the Office of Naval Research (Grant #N00014–02–1–0860), and Microsoft (Grant #2327100). Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the views of the organizations or agencies that provided support for the project.

COVER ILLUSTRATIONS: The terms “data streams” and “data rivers” are used to describe sequences of digitally encoded signals used to represent information in transmission. The left image is of the Oksrukuyik River in Alaska and the right image is an example of a crashing wave, similar to the largest recorded tsunami on Siberia’s Kamchatka Peninsula. Both images illustrate the scientific challenge of handling massive amounts of continuously arriving data, where often there is so much data that only a short time window’s worth is economically storable. The Oksrukuyik River photo is courtesy of Karie Slavik of the University of Michigan Biological Station; the tsunami photo is courtesy of the U.S. Naval Meteorology and Oceanography Command and was obtained from its Web site. Both images are reprinted with permission.