Wireless sensor networks (
) are highly distributed and concurrent, with program actions bound to external stimuli. They exemplify a system class known as
, which comprise execution units that have “hidden” layers of control flow. A key obstacle in enabling reactive system developers to rigorously validate their implementations has been the absence of precise software component specifications and tools to assist in leveraging those specifications at runtime. We address this obstacle in three ways: (
) We describe a specification approach tailored for reactive environments and demonstrate its application in the context of sensornets. (
) We describe the design and implementation of extensions to the popular
tool-chain that enable the expression of these specifications and automate the generation of runtime monitors that signal violations, if any. (
) Finally, we apply the specification approach to a significant collection of the most commonly used software components in the
distribution and analyze the overhead involved in monitoring their correctness.