Sentire represents a framework for building extensible middleware for sensor and actuator networks (SANET). The fundamental principle behind Sentire is the partitioning of SANET middleware into logically related components in order to allow developers of different aspects of the middleware to share a common plug-in infrastructure where their developed artifacts can interact. In this paper, an extended introduction of Sentire is presented, followed by a practical illustration of how this framework can be used to build SANET middleware.