Mechanism Transitions in Publish/Subscribe Systems - Adaptive Event Brokering for Location-based Mobile Social Applications

Internet traffic caused by mobile devices will exceed the traffic originating from PCs by the year 2020, according to Cisco. With a projected 61-fold increase, location-based applications and augmented reality applications exhibit the fastest growth in the mobile sector. The success of interactive augmented reality games such as Google’s Ingress or Pokémon Go is the latest indicator for the increasing popularity of location-based mobile social applications. However, the direct interaction among users and the inherent locality of this interaction in such applications pose considerable challenges to a communication system. Efficient brokering of content based on the physical location of mobile clients is further complicated by application-specific attraction points and the resulting heterogeneities and dynamics of client mobility. The publish/subscribe paradigm is well suited to model this interest-based communication pattern between users. Distinct mechanisms for both location-based filtering and locality-aware dissemination of events have been proposed for numerous application domains. However, their combined utilization and their adaptation to user mobility, network heterogeneity, and dynamic workload characteristics of mobile social applications remains an open research challenge. In this thesis, we design and implement transitions between distinct mechanisms for location-based filtering and locality-aware dissemination of events as our first contribution to address this challenge. We develop a methodology for the encapsulation of mechanisms and the execution of transitions within our publish/subscribe framework Bypass.KOM. Consequently, we apply our methodology to location-based filter schemes and dissemination mechanisms for locality-aware publish/subscribe, integrating state of the art mechanisms into Bypass.KOM. We propose distinct execution strategies for transitions, focusing on the seamless operation of the publish/subscribe system during execution by means of state transfer between mechanisms. By deriving common abstractions for transition-enabled mechanisms and the coordinated execution of transitions, we generalize our methodology as part of the Simonstrator.KOM platform. These abstractions for the design and evaluation of transition-enabled communication systems constitute our second contribution. This includes mobility and workload models for location-based mobile social applications. Based on a prototype of Bypass.KOM, we conduct an extensive evaluation of our contributions using the Simonstrator.KOM platform. We show that our state transfer mechanism and the proposed abstractions for transition-enabled mechanisms lead to a seamless execution of transitions. Additionally, we demonstrate the combined utilization of location-based filtering and locality-aware event dissemination as coexisting transition-enabled mechanisms. Overall, we show that our contributions allow the publish/subscribe system to adapt to application-specific mobility and workload characteristics by executing the respective mechanism transitions