WS-Policy is a standard to express requirements and capabilities in Web service systems. Policies are based on domain-specific assertions. In this paper we present a lightweight approach to semantic annotations of policy assertions. The approach allows matching of requirements and capabilities based not only on the syntactical representation of their corresponding assertions but also on their semantic meaning. Besides vocabulary mismatches our approach can also handle granularity mismatches, e.g. if two capabilities in combination satisfy a single requirement. We present a validation of our approach consisting of a performance evaluation and the realization of a use case, both based on our implementation of the semantic policy matching algorithm. We furthermore show the advantages of our approach compared to existing related work.