function jtree = onemsgpass( x, y, jtree, ns )
clqs = jtree{1};
seps = jtree{2};
S = get_sset( seps, x, y );
m = msgpass( clqs{x}.pot, S.pot, clqs{y}.pot, ns );
xpot = m{1};
rpot = m{2};
ypot = m{3};
% add them back into jtree
clqs{x}     = clqs{x};
clqs{x}.pot = xpot;
seps{S.id}     = S;
seps{S.id}.pot = rpot;
clqs{y}     = clqs{y};
clqs{y}.pot = ypot;
%disp(sprintf('message passed from X:%d to Y:%d (via R:%d)',...
%x,y,S.id));
jtree{1} = clqs;
jtree{2} = seps;
jtree{3} = jtree{3};