URI foafKnows = vf.createURI(FOAF.KNOWS);
// persist self and foaf:knows edges
sc.removeStatements(personURI, foafKnows, null);
for (User f : followees) {
sc.addStatement(personURI, foafKnows, vf.createURI(PersistenceContext.uriOf(new Person(f))));
}
// update timestamp
GregorianCalendar cal = new GregorianCalendar();
cal.setTime(new Date(now));