For R3, {HEAD ~ the rule} would contain {TAIL ~ a social networking URL}, such as to query for Sams bookmarks 
contain
For R3 , { HEAD ~ the rule } would contain { TAIL ~ a social networking URL } , such as to query for Sams bookmarks
OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH