  Since their recent introduction, process trees have been frequently used as a
process modeling formalism in many process mining algorithms. A process tree is
a tree-based model of a process, in which internal vertices represent
behavioral control-flow relations and leaves represent process activities. A
process tree is easily translated into a sound Workflow net (WF-net), however,
the reverse is not the case. Yet, an algorithm that translates a WF-net into a
process tree is of great interest, e.g., the explicit knowledge of the
control-flow hierarchy in a WF-net allows one to more easily reason on its
behavior. Hence, in this paper, we present such an algorithm, i.e., it detects
whether a WF-net corresponds to a process tree, and, if so, constructs it. We
prove that, if a process tree is discovered, the language of the process tree
equals the language of the original WF-net. Conducted experiments show, that
the algorithm's corresponding implementation has a quadratic time-complexity in
the size of the WF-net. Furthermore, the experiments show strong evidence of
process tree rediscoverability.
