This book reports on a novel concept of mechanism transitions for the design of highly scalable and adaptive publish/subscribe systems. First, it introduces relevant mechanisms for location-based filtering and locality-aware dissemination of events based on a thorough review of the state-of-the-art. This is followed by a detailed description of the design of a transition-enabled publish/subscribe system that enables seamless switching between mechanisms during runtime. Lastly, the proposed concepts are evaluated within the challenging context of location-based mobile applications. The book assesses in depth the performance and cost of transition execution, highlighting the impact of the proposed state transfer mechanism and the potential of coexisting transition-enabled mechanisms.