Translating WFS Query to SQL/XML Query

The purpose of the WFS specification, proposed by the the OpenGIS Consortium (OGC), is to describe the manipulation operations over geospatial data using GML. Web servers providing WFS service are called WFS Servers. WFS servers publish GML views of geographic features stored in data sources such that the user can query and update data sources through a user defined feature type schema. In this work, we study the problem of answering WFS queries through a feature type schema, when the data is stored in a relational database. A feature type is specified by the feature type schema and a set of correspondence assertions. The feature type's correspondence assertions formally specify relationships between the feature type schema and the relational database schema. We define the semantic for WFS query answering and present an algorithm that translate a WFS query defined over a feature type schema into a SQL/XML query defined over the relational database schema.