An example of a Petri net (a fragment). The semantics of the places and transitions of this Petri net is defined through the use of EXACT2. Two experimental actions streak and transfer, defined in EXACT2, are used as labels to represent the semantics of the transitions. The descriptors of those experimental actions and their values, e.g. equipment: 10 ml glass pipette are used to represent the semantics of the places. The tokens (dark dots) indicate the necessary conditions for the transitions to take place.