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Behavioral Comparison of Process Models Based on Canonically Reduced Event Structures. Paolo Baldan Marlon Dumas Luciano García Abel Armas. Behavioral comparison of process. Explain the differences between a pair of process models using simple and intuitive statements
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Behavioral Comparison of Process Models Based on Canonically Reduced Event Structures Paolo Baldan Marlon Dumas Luciano García Abel Armas
Behavioral comparison of process • Explain the differences between a pair of process models using simple and intuitive statements • Abstract representations based on binary behavioral relations • Event structures, e.g., PES and AES • More expressive formalisms can give smaller representations • AES can provide smaller representations than PES
Comparison based on reduced AES • Folding technique does not ensure canonicity • Canonical graph labeling technique • Process models can represent infinite behavior. I.e., cyclic behavior. • Unfolding technique for computing a finite representation • Provide understandable feedback about behavioral discrepancies • Error tolerant graph matching techniques • Categorization of discrepancies
Background. Petri nets Silent transition Transition • Markings: {{p0}, {p1}, {p2}, …} • Firing sequence: {{a,b, …}, …} • Executions: {{a,b,c,d}, …} Place
Background(2). Branching process and PES Configurations: {{a},{a,b},{a,c},{a,b,c}, …}
Background(3). PES and AES • AES is a more expressive formalism than PES • Same configurations as PES, but fewer events • Reduction technique (folding) • hp-bisimilarity • Non-canonicity
Canonical graph labeling technique • Canonical graph labeling techniques (McKay‘s algorithm) • Associates a graph with a canonical label • Largest lexicographical exemplar of the (string linear representation) adjacency matrix • Keep the order given to the vertices in the largest exemplar • Compute the canonical graph labeling for PES • Weight of the events
Canonical folding • Folding of events • Lexicographic order on the event’s label • Largest set of events • Largest weights w.r.t. the canonical graph labeling
Cyclic process models • Infinite number of events in branching process • Infinite number of events in PES • Finite complete prefix unfoldings
Finite complete prefix unfolding • McMillan and Esparza • Truncating techniques based on markings • Does not reflect all the possible causal predecessors for any event
Customized complete prefix unfolding • Khomenko et al. proposes a framework to define a customized complete prefix unfolding • Order for configurations • Set of configurations • Equivalence • Equivalence for capturing causal dependencies • Same markings • The marking was generated by the firing of the same transitions
Customized complete prefix unfolding(2) • Cyclic behavior: • A transition c is part of cyclic behavior if there is a configuration with two occurrences of c • Transition c is repeated 1 or more times if it occurs in all runs • Transition c is repeated 0 or more times if it does not occur in all runs
Not canonical unfolding • It does not guarantee a canonical complete prefix unfolding for equivalent models (pomset-trace equivalence)
Comparison • Relations among matched events • In model 2, there is a state after the execution of task cwhere d and c are mutually exclusive; whereas in model 1, there is a state after the execution of b where c can occur before d, or c can be skipped • In model 2, there is a state after the execution of task a where c can occur before d, or c can be skipped; whereas in model 1, there is a state after the execution of a where c precedes d • Mismatching repetitive behavior • Task b may occur many times in model 2; whereas in model 1, it is not repeated any time • Task c may occur many times in model 2; whereas in model 1, it is not repeated any time • Unmatched events • There is an additional occurrence of task bafter c in model 2 • There is an additional occurrence of task cafter b in model 2
Conclusions • Technique for a behavioral comparison of process models using AES • Canonical folding of AES • Finite representation using Petri net unfoldings • Characterization of cyclic behavior according to task repetitions • Categorization of discrepancies for offering a more understandable feedback
Future work • Visualization of discrepancies in the models • Empirical evaluation of the usefulness of diagnostics using real-world process models • Test if a more refined feedback can be given by using other models of concurrency
Comparison • Consider only common behavior (common labels of tasks) • One model can have more behavior than other • Error tolerant graph matching techniques • Discrepancies • Mismatching relations among matched events (approximate context) • Mismatching repetitive behavior • Unmatched events (approximate context)