Wireless sensor networks can be considered as a tool for detecting certain 
states in the real world. We examine the use of event-based systems for this 
task. In the literature, a number of event-notification systems have been 
presented that facilitate the specification and automatic detection of event 
patterns - so-called composite events. While events are a valuable 
abstraction in sensor networks, we show that composite events are less suited 
to detect real-world states with sensor networks. We illustrate an alternate 
solution that retains the advantages of an event-based approach, but which 
provides better support for the specification and detection of real-world 
states.