Fig. 3
From: From the desktop to the grid: scalable bioinformatics via workflow conversion
A workflow as represented by a Petri net. Petri net modelling a software pipeline to protonate a molecule found in a single input file. Places are shown as circles, transitions are depicted as squares. The place P 0 expects and contains one token, represented by a black dot, and is thus enabled. It follows that P 0 is the starting place and P 4 represents the end of the process