The event-driven, or notification-based, paradigm has attracted much research interest in areas such as distributed systems, databases, workflow, and grid computing. However, little attention was devoted to event-driven service-oriented architectures (SOAs). In this paper, we propose a novel framework for event-based interactions in SOAs. Our contribution in this paper is threefold. First, we introduce various notification patterns for event-driven SOAs. We define two taxonomies for dissemination protocols in SOAs: the interaction taxonomy identifies the different models through which Web services interact with each other; and the filtering taxonomy classifies the events and services involved during dissemination. Second, we propose a dissemination pattern called implicit notification. In contrast to publish-subscribe, implicit notification does not require consumers to explicitly subscribe with producers. We define a model for implicit notifications and introduce a family of protocols for enabling this pattern. Finally, we describe a prototype implementation for a disaster management case study and conduct experiments to assess the performance of the proposed protocols.