R := {[t,s] -> [t+1,s] } union
 {[t,s] -> [t,s] } union
 {[t,s] -> [t,s+1] };

R;
R+;

S := {[t,s] -> [t+1,s] } union {[t,s] -> [t,s+1] };

S;
S+;