Recently, a new class of data management applications has emerged in areas such as sensor-based environmental monitoring, financial services, network monitoring, and military applications. These stream processing applications require low-latency processing of large-volume data streams. Because traditional database management systems are ill-suited for high-volume, low-latency stream processing, new systems, called stream processing engines (SPEs), have been developed.  In this talk, Magdalena Balazinska presents the software architecture and algorithms in Borealis, one of the first distributed stream processing engines. From the Series:CSE Colloquia - 2005