Research On Publish/Subscribe On Internet

The Internet is evolving from a network for information exchanging and sharing to a most pervasive distributed computing environment. The main characteristics of the Internet-scale distributed computing are large-scale, decentralized control, dynamic and autonomous. Since publish/subscribe (P/S) systems have the advantages of loose coupling, anonymity, many-to-many communication and scalability, they have become important infrastructure middleware platforms support for the Internet-scale distributed computing.However, existing P/S systems suffer a number of problems on the efficiency, expressiveness and usability, which make them not directly applicable in the Internet-scale computing environment. Based on the brief analysis of the principles, applications and key technologies of P/S systems, this thesis focuses study on the network topology, routing algorithms, composite event detection, and design of P/S services under the object-oriented environment.1) A constant-congestion hierarchical topology model for overlay networks is proposed in chapter 3. Considering the scalability of topology which is necessary in the Internet-scale computing environment, An incomplete hierachical graph (IHG) is defined based on the hierarchical topology model. The properties of IHG are analyzed, and that IHG with the shortest path routing is constant congestion is proved. The simulation indicates that IHG provides low mean-latency at high throughput for transmitting messages. The results imply that IHG, despite its structural nonhomogeneity, can easily be constructed that any potential congestion links are avoided, ensuring good scalability.2) In chapter 4, a new content-based routing (CBR) approach called ROSE, i.e. routing on subscription-forwarding and events-flood, is proposed to realize CBR in large scale publish-subscribe systems. ROSE relies on a ring space where subscriptions and events are routed along distinct, albeit intersecting, partitions. An analytical model of ROSE is derived, and validated through simulation. Then ROSE_Scale is defined as a sparse ROSE model, and a reconfiguration strategy for subscription tables is proposed, which is based on the notion of composition and decomposition from ROSE_Scale. The simulation results show that ROSE achieves efficient CBR even in large scale settings while at the same time opening up opportunities for deployment-time tuning based on the expected traffic profiles.3) In chapter 5, an active subscription mechanism (ASM) based on active rules is addressed to provide a composite event detection model that suits many classes of applications with interests in temporal and spatial events. An event-based framework with a layered architecture is proposed, which includes network layer, P/S layer, and application layer. The use of P/S layer allows the framework to offer easy integration with existing P/S systems. Then a composite event model based on active subscription rule (ASR) is designed, four types of semantic aggregations are defined, and distributed processing problems are discussed by the decomposition and distribution of each individual ARS. Performance evaluation examines benefits with respect to three system resources: processing, communication, and storage, and demonstrates that ASM with ASRs provides an expressive and scalable solution for distributed systems.4) In chapter 6, a design of event and subscription models under an object-oriented environment is motivated by the idea of using P/S paradigm for an object-oriented environment. A P/S service on the basis of Delphi and its object model is studied. The P/S service is comprised of two subsystem-compiler and executor. In each subsystem, its form, working process, and typical algorithms are analysed from the point of object-oriented and technology of P/S paradigm separately. Experiments are simulated in the following three aspects:user's model, middle code generation and execution, and show that using the P/S service improves the usability of P/S systems.