BPMN: How much does it cost? An Incremental Approach

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BPMN How much does it cost? An Incremental
Approach

• Matteo Magnani magnanim_at_cs.unibo.it
• Danilo Montesi montesi_at_cs.unibo.it
• University of Bologna Italy
• Presented by Fabrizio Riguzzi University of
  Ferrara - Italy

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Introduction

• Business Process Modeling Notation (BPMN)
• Aim of the work extending BPMN with cost metrics.

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Costs (assumptions)

• Additive costs the cost of any two tasks is the
  sum of their costs.
• E.g. , the money spent to perform a task.
• Other kinds of cost have been studied (e.g.,
  time-performance).

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Modeling costs

• We extend all BPMN constructs with cost intervals
  and average costs,
• and propose several methods to compute the
  overall cost of a diagram.

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Related approaches

• To the best of our knowledge, no other extensions
  of BPMN.
• However, many works on related modeling
  languages, based on simulation.
• Simulation is used because no general efficient
  analytical methods exist.

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Our approach

• BPMN diagrams can be very complex!
• the free-form nature of BPMN can create modeling
  situations that cannot be executed or will behave
  in a manner that is not expected
• We have identified classes of diagrams capturing
  the most typical processes and for which
  efficient analytical solutions exist.

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Class 1 ST-IP (cost intervals)

• Single-Token Independent Processes.
• Represents a single token created at the start
  event and traversing the diagram until it is
  consumed.
• ST-IP diagrams with cost intervals can be
  translated to directed graphs.
• The minimum and maximum costs can be computed as
  the shortest (Dijkstras algorithm) and longest
  path.

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Class 1 ST-IP (example)
Shortest Path
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Class 1 ST-IP (example)
Longest Path
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Class 1 ST-IP (average costs)

• When intervals diverge (as in the previous
  example), we can use average costs, together with
  the probability of alternative paths.

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Class 1 ST-IP (example)

• The overall cost can be expressed as a non
  homogeneous linear equation system
• C(i) average cost for a token to start in node
  i and to reach the end event

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Class 1 ST-IP (example)
C(1) 0 C(2) C(2) 2 C(3) C(3) 0 .5
C(4) .5 C(5) C(4) 2 C(5) C(5) 1
C(6) C(6) 0 .9 C(7) .1 C(2) C(7) 0
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Class 2 ST-N-IP

• Single-Token NESTED Independet Processes
• Diagrams with sub-processes all reducible to
  ST-IP.
• The computation of costs can be done recursively,
  by computing the cost of each sub-process and
  substituting it in the diagram above.

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Class 3 MT-ME-N-IP

• Multiple-Token Multiple-End Nested Independent
  Processes.
• Multiple tokens -gt parallelism.

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Summary

• Managing costs in BPMN diagrams useful but
  complex.
• However, we may define classes reducing to
  well-known problems.
• ST-IP, cost intervals
• Dijkstra
• Longest path
• ST-IP, average costs non homogeneous equation
  systems
• ST-N-IP iterations of the previous approaches
• MT-ME-N-IP sumprobabilities

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BPMN How much does it cost? An Incremental
Approach

• Matteo Magnani magnanim_at_cs.unibo.it
• Danilo Montesi montesi_at_cs.unibo.it
• University of Bologna - Italy