Event data messages can be provided by an interactive voice response (IVR) system to a complex events processor (CEP). The event data messages can include a Stream_ID and a series of textual elements. The Stream_ID can uniquely identify a call session between a caller and the IVR system. The series of textual elements can represent speech input provided by the caller. The CEP can create a text string from the series of textual elements of event data messages having the same Stream_ID. The text string can inherit the Stream_ID of the event data messages. The CEP can utilize user-defined business rules to process the text string. When the CEP issues an action message, the Stream_ID of the text string can be appended to the action message sent to the IVR system. The IVR system can modify the call session associated with the Stream_ID of the action message accordingly.