Query evaluation and presentation planning within a spatial mediator: extending XML-based mediation to heterogeneous sources of GIS and imagery data

This paper reviews challenges and accomplishments of spatial information mediation extending the SDSC MIX (mediation of information using XML) framework. enhancements to MIX necessitated by the spatio-temporal nature of queries and underlying GIS and imagery data sources, include mediator-level development of query evaluation and results presentation strategies which take into account the source data quality and query context, and define integrated views over heterogeneous sources in terms of mediation algebra for spatial types (MAST). Development of query and presentation plans at the spatial mediator is based on source schema and query capability descriptions exported by source wrappers. A set of tools supporting XML-based spatial markup, query and presentation is also introduced