Combining heterogeneous spatial data from distributed sources

The general problem of retrieval and integration of data from a set of distributed heterogeneous data sources in response to a query has a number of facets. These include the breakdown of a query into appropriate subqueries that can be applied to different data sources as well as the integration of the partial results obtained to produce the overall result. The latter process is non-trivial and particularly dependent on the semantics of the data. This paper discusses an architecture developed to enable a user to query spatial data from a collection of distributed heterogeneous data sources. This has been implemented using GML to facilitate data integration. The system is currently being used to study the handling of positional uncertainty in spatial data in such a system.