{HEAD ~ A highly scalable, flexible, and extensible mechanism} is provided for authenticating {TAIL ~ a request} from a client 
is provided for authenticating
{ HEAD ~ A highly scalable , flexible , and extensible mechanism } is provided for authenticating { TAIL ~ a request } from a client
HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH