Context awareness has emerged as an important element in distributed computing. It offers mechanisms that allow applications to be aware of their environment and enable these applications to adjust their behavior to the current context. Considering the dynamic nature of context, the data flow of relevant contextual information can be significant. In order to keep track of this information flow, a flexible service mechanism should be available for the client applications. In this document we present a service-oriented middleware for context-aware applications. This middleware provides support to leverage the development of context-aware applications by providing a scripting-like approach for context-aware application development; allowing the subscription of rules containing context-based events and conditions and a notification to be sent when the specified context holds. Moreover, a domain-specific language has been developed to express these context-based rules.