EPL lets you create queries that operate on streams of items to generate more valuable streams that contain derived items. Derived items can be events, location types or simple types (boolean, decimal, float, integer, string). In stream queries, you can use standard relational operations, such as filters, joins, aggregation, and projection, to generate items. For example, you can define a query that converts a stream of raw tick data into a stream of volume-weighted average price (VWAP) items.

Stream-based language elements allow operations that refine events to be expressed more clearly and concisely than when using procedural language constructs such as event listeners. In particular, applications that need to calculate one value based on multiple items from an input stream are simpler and more efficient when written with stream queries.

Apama provides sample code that uses streams and stream queries in the samples/monitorscript directory of your Apama installation directory. There is also an introductory whitepaper, Apama EPL Streams: A Short Tour, available in the doc\pdf directory of your Apama installation directory.