The integration of event information from diverse event notification sources is, as with meta-searching over heterogeneous search engines, a challenging task. Due to the complexity of event filter languages, known solutions for heterogeneous searching cannot be applied for event notification In this paper, we propose the concept and design of a Meta Service for Event Notification. We define transformation rules for exchanging event filter definitions and event notifications between various event services and sources. We transform each filter defined at a meta-service into a filter expressed in the language of each event notification source. Due to unavoidable asymmetry in the semantics of different langues, some superfluous information may be delivered to the meta-service. These notifications are then post-processed to reduce the number of spurious messages. We present a survey and classification of filter languages for event notification, which serves as basis for the transformation rules. The proposed rules are implemented in a prototype transformation module for a Meta Service for Event Notification.