The following articles provide background information on the URR and the data model of the URR:
Plag, H.-P., Foley, G., Jules-Plag, S., Kaufman, J., Ondich, G., 2012. The GEOSS User Requirement Registry: A Versatile Tool for the Dialog Between Users and Providers. Preliminary Proceed. of IGARSS 2012, Munich, Germany, July 23-27, 2012. Available as pdf.