Processing XPath Queries With Forward and Downward Axes Over XML Streams

While databases process volatile queries over persistent data, the emerging technology of stream processing aims to handle persistent queries against incoming volatile data streams. Of particular interest, XML streams are expressed in a platform-neutral format, so they are suitable for data archiving or publication on the web. Typical application areas of XML streams are scientific data (astronomical data, protein sequence data), control streams (sensor stream, air traffic, ATM monitoring), and data archiving for analysis (click streams on the Internet, personal log, linguistic TreeBank database).