About: http://webisa.webdatacommons.org/69536735

Property	Value
http://www.w3.org/1999/02/22-rdf-syntax-ns#type	http://www.w3.org/ns/prov#Entity
http://www.w3.org/ns/prov#value	If by $x1$ you mean the first coordinate of $x$, then the set consists actually of those vectors whose all other coordinates except possibly the first are zero.
http://www.w3.org/ns/prov#wasQuotedFrom	stackexchange.com