A Flexible, Scalable, Distributed, Fault Tolerant Architecture for the Collection and Dissemination of Multimodal Traffic-Related Information
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Intelligent Transportation Systems (ITS) produce considerable quantities of dynamic data. ITS endusers will require wide, rich and highly available services which will involve processing and disseminating large amount of multimodal information. Dissemination of dynamic (time-varying) traffic data have an associated a temporal coherency requirement (tcr), which depends on the nature of the data and user tolerances. This thesis aims to design and prototype a flexible, scalable/adaptable, distributed, fault-tolerant architecture to be used as a framework to develop future ITS services for the collection and dissemination of traffic related information. Requirements have been collected from the actual European ITS framework architecture (KAREN) and Dublin City Council. The architecture prototypes an end-user service for the dissemination of car parking data. A more detailed and specific multi-tier architecture is designed and prototyped. Proxy servers can be deployed in a configured clustered environment, thereby ensuring scalability, reliability, faulttolerance, and the full use of multiple machines while avoiding bottlenecks. Most attention is devoted to the replication and availability mechanisms in the system so that individual implementations can grow and adapt with local requirements. A new hybrid Lazy Pull and Push Algorithm is devised and implemented. The algorithm is adaptive and can be tuned dynamically to suit data of varying urgencies and varying frequencies of update. Information is manipulated and presented under cross-platform and system independent XML standards, providing compatibility of information to end-users through different media. Application crosscutting concerns have been addressed using an Aspect Oriented Software Development (AOSD) approach in the implementation. Preliminary performance measurements are presented with possible scenarios to illustrate the versatility of the architecture and the degree to which it can be tailored to local, geographic requirements. Suggestions are proposed and described for future work that will enhance the actual system architecture.
Author: Olias-Sanz, Alfonso
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