Fundamental to the operation of a geoportal are metadata, the catalogue entries that allow users to search for datasets and to assess their contents. Metadata may include information on contents, quality, the data production process, details of formats and coordinate systems, and many other topics. For more details see the UK Geospatial Information Gateway: http://www.gigateway.org.uk/ or the US National Spatial Data Infrastructure site: http://www.fgdc.gov/nsdi/nsdi.html