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Browsing by Author "Fetterer, Andrew"

Now showing 1 - 2 of 2
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    Materialization Trade-Offs in Hierarchical Shortest Path Algorithms: A Case Study in ATIS
    (1997) Shekhar, Shashi; Fetterer, Andrew; Goyal, Brajesh
    Materialization and hierarchical routing algorithms are becoming important tools in querying databases for the shortest paths in time-critical applications like Intelligent Transportation Systems (ITS), due to the growing size of their spatial graph databases (23]. A hierarchical routing algorithm deccmposes the original graph into a set of fragment graphs and a boundary graph which summarizes the fragment graphs. A fully materialized hierarchical routing algorithm pre-computes and stores the shortest-path view and the shortest-path-cost view for the graph fragments as well as for the boundary graph [13]. The storage cost of the fully materialized approach can be reduced by a virtual or a hybrid materialization approach, where few or none of the relevant views are pre-computed. This paper explores the effect of n ,aterializing inruvidual views for the storage overhead and computation time of hierarchical routing algorithms. Our experiments with the Twin Cities metropolitan road-map show that materializing the shorte;t-path-cost view for the boundary graph provides the best savings in computation time, for a given a.mcunt of storage and a small number of fragments. Materializing the relevant part of the shortest-path-cost view for the fragment graphs provides the next best savings, followed by materializing the shortest-path view for the boundary graph. Virtual shortest-path-view on fragments can reduce storage costs by an order of magnitude or more for large graphs.
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    Multimedia Information Presentation in Smart Cars and Highways
    (Minnesota Department of Transportation, 1995-06) Shekhar, Shashi; Fetterer, Andrew; Kalantar, Maryam
    An essential component of Advanced Traveler Information Systems, in-vehicle route displays give drivers route options, alert them to incidents, and show their present location. In this report, researchers explore multimedia interfaces to present route information to travelers using map, text, and auditory-based representations, focusing on developing portable multimedia interfaces. The report concludes that the graphical user interface (GUI) for display of route information is satisfactory for small road maps. The GUI also proved useful for visually checking map quality. The Tcl/Tk toolkit, in which the GUI was developed, is a reasonable tool to design an interface because it is portable to many platforms. Speech generation tools are not yet robust enough for use with large maps. Future work could include extending the GUI to provide a hierarchical display for large roadmaps, extending the amount of information conveyed to the user, and improving speech generation techniques.