Querying VGI by semantic enrichment

Volunteered geographic information (VGI) plays an increasing role in current geodata provision. At the same time, due to its lack of structure, it is hard to use as meaningful input in software applications. In this chapter, we embark upon the unstructured character of VGI and on ways to enrich the structure in order to make it suitable for information retrieval. We describe the charac-teristics  of  semantic  enrichment  and  explain  how  folksonomies  and  ontolo-gies  play  a  role.  We  believe  that  they  represent  different  levels  of  formality  in a semantic reference space and determine the richness of the information retrieval.