The foaf:loaf property relates a foaf:Person to a LOAF foaf:Document. The LOAF document format is designed to encode a representation of an email addressbook without compromising privacy. It can be used for mail filtering and prioritisation, and for social network analysis. See the LOAF site for details and an example file. A related approach is the FOAF whitelists experiment, which also uses hashed mailbox identifiers for spam-filtering.