The organization of WISEN attests to the growing interest among many different communities in the problem of how to provide efficient delivery of event notifications on an Internet scale. But what exactly is "event notification", and what exactly does "Internet scale" mean? Each community has its own interpretation of these terms, and the interpretations typically reflect the specific needs of the community. In this talk I will offer a characterization of Internet scale event notification that is intended to be acceptable to the broad range of communities represented at WISEN.