“…Let us denote the trace vertices (i.e., circles themselves) by y b , y a and y c (for the implementation) and x a , x b , x c and x d (for the specification). The implementation vertices are not causally related to each other, while the specification vertices are partially ordered (the precedence relation is drawn by arrows: x a ≺ x c , x b ≺ x c , x a ≺ x d and x b ≺ x d ) and are tagged with time intervals (δ (x a ) = [0, 2], δ (x b ) = [1,3], δ (x c ) = [0, 4] and δ (x d ) = [1,5]). Matchings are depicted by intermittent lines connecting the implementation vertices with the specification ones ((x a , y a ), (x b , y b ) and (x c , y c )).…”