Example: PICS Labels
PICS includes a schema, statements (about pages), and metastatements (about labels)
(PICS-1.1 "http://www.gcf.org/v2.5" by "John Doe" labels on "1994.11.05T08:15-0500" until "1995.12.31T23:59-0000"
for "http://w3.org/Overview.html" ratings (suds 0.5 density 0 color/hue 1)
for "http://w3.org/Underview.html" by "Jane Doe" ratings (subject 2 density 1 color/hue 1))
[hypothetical; this is not a standards proposal]