The following four optimization problems over a finite set of traces are considered: (i) find the longest trace that is included in each trace from a given finite set T of traces, (ii) find the shortest trace that is not included in every trace from a given finite set T of traces, (iii) find the shortest trace that includes every trace from a given finite set T of traces, (iv) find the longest trace that does not include each trace from a given finite set T of traces.