x1=b2=p3 is a (predicate) equivalence relationship/similarity/parallel with/between/among arguments (sequence(s)/set(s)) x2=b3=p1=p2, partitioning (with only empty intersection) set/structure x3=p4; elements of x2 are mutually similar in property x1 within structure x3; x3 is partitioned by x1 into equivalence classes (including) x2;
An equivalence relation is reflective, symmetric, and transitive. Likewise for the first two terbri of panra. Therefore, order of x2 is unimportant. See also: panra, panrykle, terpanryziltolju'i