Let x , y be sets. Let R be a binary relation. A finite sequence is called a reduction sequence w.r.t. Let R be a binary relation. Note that every reduction sequence w.r.t.
R is non empty.
Let R be a binary relation and a , b be sets. Let R be a binary relation and p be a reduction sequence w.r.t. For all binary relations R , Q such that R Q holds every reduction sequence w.r.t. R is a reduction sequence w.r.t.