A stream variable references a linearly ordered flow of items that have been processed by the correlator. The items in a stream are always ordered according to the order in which the correlator processed them. When more than one item arrives in a lot the correlator preserves the order in which it processed them.

An item in a stream can be any Apama data type. A particular stream can contain only one type of item.

The optional initializer can be a stream source template, a stream query definition, or any other expression that returns a stream. A stream source template is an event template that specifies the all keyword and no other qualifiers. See Stream source templates. A stream query definition specifies a query that the correlator applies continuously to one or two streams. See Stream queries.