Accuracy Mediation within a Spatial Wrapper-Mediator System

Query evaluation strategies in traditional databases do not consider possible data inaccuracy and vagueness of predicates. However, measurement considerations and data quality are inherent components of geographic information. The purpose of this work is to explore query evaluation in distributed spatial information mediation system that takes into account different accuracy characteristics of data sources. A mediator-based system is a data integration architecture that supports homogeneous views over heterogeneous sources. A 'spatial mediator' is software that can dispatch portions of a user query to multiple sources of XML-wrapped spatial data and services, and assemble query results (as described in Gupta et al., 1999). We explore the following research questions: (1) how accuracy specification can be formulated as part of a query; (2) how accuracy information is used by the spatial mediator for selecting sources and determining query evaluation plans, and (3) how accuracy considerations and query results are exposed to the user.