[eclipse 4]: S `:: {e(a,10), e(b,15)} ..{e(a,10), e(b,15), e(c,20)}, sum_weight(S, W). S = S{{e(a, 10), e(b, 15)} .. {e(a, 10), e(b, 15), e(c, 20)}} W = W{[25..45]} Delayed goals: weight_s(S{{e(a, 10), e(b, 15)} .. {e(a, 10), e(b, 15), e(c, 20)}}, W{[25..45]}) yes.