.PS
.ps 20
## figure 2
boxwid = 4 * boxwid
boxht  = 2 * boxht
B1:	box height boxht*7/4
B2:	box with .n at (B1.s.x, B1.s.y-lineht) "\normalsize RTS"
B3:	box with .n at (B2.s.x, B2.s.y-lineht) "\normalsize SESSION"
	line dotted from B1.n to B1.s
	line from B1.s to B2.n "\ bulk datastructures" ljust
	line from B2.s to B3.n "\ dialogues" ljust
##
boxwid = boxwid / 4
boxht =	 boxht / 2
B1a:	box with .w at (B1.w.x+boxwid/2, B1.w.y) "P1"
B1b:	box with .ne at (B1.ne.x-boxwid/2, B1.n.y-boxht/2) "P3"
B1c:	box with .se at (B1.ne.x-boxwid/2, B1.s.y+boxht/2) "ROS"
	line from B1b.s to B1c.n
##
.PE