{HEAD ~ The system} also includes {TAIL ~ a subscription mechanism} that sends a subscription message to a notification mechanism 
includes
{ HEAD ~ The system } also includes { TAIL ~ a subscription mechanism } that sends a subscription message to a notification mechanism
HEAD HEAD HEAD HEAD HEAD HEAD OTH REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH