"The Evolution of Internet-Scale Event Notification Services: Past, Present, and Future" #readingToday This paper sought an evolutionary explanation of the popularity of collaborative applications coordinating through event-based implicit invocation, its current challenges, and likely next steps. From the past, we discerned a common trend of widening range -- from single hosts to local-area networks to wide-area networks -- within each of five application themes employing events as notification messages that trigger commands: information distribution, presence, conferencing and instant, simulation and graphics, and inter-application integration. Academic literature in the area can be reinterpreted to separate applications using Event Based Integration from underlying Event Notification Services.ENS at the present moment require less about adapting to ever-widening geographic, temporal, and numeric scales, than to the trust boundaries uniquely defining "Internet-Scale." New tensions are surfacing in bridging dissimilar ontology, security, and mobility models. Furthermore, the politics and economics of Internet scale are dominated by the "network effect" -- the tendency for a common, inter-operable standard to become more valuable precisely in proportion to the numbers of developers and applications using it.We recommend a layered Interent-Scale ENS wire protocol for notifications, perhaps as an asynchronous version of HTTP with hooks for notification management, interfaces for advertising and subscribing, policies for information queue management, generic notification typing, notification trapping based on methods and resources, link maintenance, and capabilities for new-content push.