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Context information is vital data coming from mobile devices to add a value for the application execution. Such applications are called context-aware or context-sensitive applications. To enable context-aware applications in a distributed environment, first the context raw data is measured from sensors. After interpreting and structuring the data, the context objects have to be disseminated all over the distributed system. This paper introduces a context dissemination middleware based on a mobile Web Service framework. It eases the development of context aware applications by providing an abstraction layer hiding complex protocols. In addition, the protocols are optimized in terms of reducing latencies and network load. Moreover, to provide observation (monitoring) service of arbitrary context information, a rule description (policy) language has been designed, developed and structured. Web services eventing has been implemented for sending event notifications. The architecture and a prototypical implementation of the context middleware is presented in detail.