TITLE:

Storage and Access Methods for Spatial Graphs (e. g. Navigable Road-Map Databases)

PRESENTER:

Shashi Shekhar

AFFILIATION:

Computer Sc. Dept., CTS and AHPCRC, Univ. of Minnesota.

TECHNICAL ABSTRACT:

Current Spatial Database Management Systems (SDBMS) provide efficient access methods and operators for point and range queries over collections of spatial points, line segments, and polygons. However, it is not clear if existing spatial access methods can efficiently support network computations which traverse line-segments in a spatial network based on connectivity rather than geographic proximity. The expected I/O cost for many network operations can be reduced by maximizing the Weighted Connectivity Residue Ratio (WCRR), i.e., the chance that a pair of connected nodes that are more likely to be accessed together are allocated to a common page of the file. CCAM is an access method for general networks that uses connectivity clustering. CCAM supports the operations of insert(), delete(), create(), and find() as well as the new operations, get-A-successor() and get-successors(), which retrieve one or all successors of a node to facilitate aggregate computations on networks. The nodes of the network are assigned to disk pages via a graph partitioning approach to maximize the WCRR. CCAM includes methods for static clustering, as well as dynamic incremental reclustering, to maintain high WCRR in the face of updates, without incurring high overheads. We also describe possible modifications to improve the WCRR that can be achieved by existing spatial access methods. Experiments with network computations on the Minneapolis road map show that CCAM outperforms existing access methods, even though the proposed modifications also substantially improve the performance of existing spatial access methods.

KEYWORDS:

Storage/Access Methods, Spatial Databases, Navigable Roadmaps, Traveler Info. Systems., Intelligent Transportation Systems.

NOTE:

Some of the results discussed in this talk appeared in the following recent publication: "CCAM: A Connectivity-Clustered Access Method for Networks and Network Computations", IEEE Trans. on Knowledge and Data Engineering, 9(1), Jan.-Feb. 1997.