BPM Milan: Refined Process Structure Tree

Jussi Vanhatalo of the IBM Zurich Research Lab presented a paper on the Refined Process Structure Tree, co-authored by Hagen Voelzer and Jana Koehler. We’re in the last section of the day, on formal methods.

The research looks at the issues of parsing a business process model, and they offer a new parsing technique called the refined process structure tree that provides a more fine-grained model. Applications for parsing include:

  • translating a graph-based process model (e.g., BPMN) into a block-based process model (e.g., BPEL)
  • speeding up control-flow analysis
  • pattern-based editing
  • processing merging
  • understanding large process models
  • subprocess detection

He showed us an example of the last use case, subprocess detection, where sections of a process are detected and replaced by subprocesses, making the process more understandable (as we saw in the earlier paper on modularity).

There are a few requirements for parsing:

  • uniqueness: e.g., the same BPMN model is always translated to the same BPEL process
  • modularity: e.g., a local change in BPMN translates to a local change in BPEL
  • fast computation of parse tree, e.g., for process version merging, pattern-based editing, or control-flow analysis
  • granularity

The Normal Process Structure Tree, which they have presented in earlier research, is both unique and modular, and represents a hierarchy of canonical (non-overlapping) fragments. Its computing time is linear.

The Refined Process Structure Tree uses a relaxed notion of a fragment through specific definitions of boundary (entry and exit) nodes, and allows only for non-overlapping fragments that can be assembled into a hierarchy. Like the NPST, it is unique and modular, but is more fine-grained than the NPST (presumably because of the relaxed definition of a fragment). It can also be computed in linear time, and he walked through a linear time algorithm for computing the RPST.

In this paper, they assumed that there is only one start and one end node in a process, and that loops have separate entry and exit node; since the publication of this paper, their research has progressed and they have lifted both of these restrictions.

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