Architecture

The following figure shows the function flow of Web Feature Service (WFS) with a solution of schema transformation. When users pose query based on a comprehensive schema (step 1), e.g., FGDC geodetic control schema, a schema mediator (wfs emu) transforms the standard schema to local schema (step 2), Web server will process the transformed user query and send WFS request to every database (step 3). Once WFS response are returned from local databases (step 4), local schema again are transformed back to the standard schema (step 5) before WFS query results are provided to a user (step 6). Schema transformation can be based on languages such as the Extensible Stylesheet Language Transformations (XSLT), or the Streaming Transformations for XML (STX), which are further discussed in another section.