Hans Gilde is scornful. In Predictive analytics, CEP and your local mechanic, he points out that the key capability for an effective predictive system is "a solid foundation for ongoing critical analysis of the effectiveness of your analytics".
I would extend his scorn to anyone who uses the term "real-time" in a sloppy and confused manner. I keep reading about "real-time complex event processing", but in many cases it looks as if much of the complex processing is actually done at design-time, leaving the real-time portion fairly quick and simple. And that's probably as much as the current state-of-the-art technology can manage.
To do predictive analytics properly, as Hans says, you need critical analysis - what is sometimes called double-loop learning. How does a CEP system learn new patterns? How does a CEP get recalibrated as the environment evolves? How do we control (and reduce) the level of false positives and false negatives? And how much of this analysis does it make sense to even attempt in real-time?
So I looked at a recent paper in the IBM Systems Journal, Generating real-time complex event-processing applications (Volume 47, Number 2, 2008).
"Complex event processing (CEP) enables the extraction of meaningful and actionable information from event streams. The CEP technology is intended to provide applications with a flexible and scalable mechanism for constructing condensed, refined views of the data. CEP correlates the data (viewed as event streams) in order to detect and report meaningful predefined patterns, thus supplying the application with an effective view of the accumulated incoming data (events), and allowing the application to react to the detections by executing actions."
The IBM paper talks about some of the challenges of achieving genuine real-time data extraction based on predefined patterns, and talks about the possibility of real-time CEP applications, but is careful not to make any larger claims.
Other writers are not so careful, and you can find lots of websites promising real-time predictive analytics or real-time decision-making. But there are not only technological but conceptual limits to what you can do in real-time.