1. a 14← department of mathematics and computer science PROSE 05-10-06 1 Checking Properties of Adaptive Workflow Nets K. van Hee, I. Lomazova, O. Oanea, A. Serebrenik, N. Sidorova, M. Voorhoeve Program Systems Institute of the Russsian Academy of Science

2. a 14← department of mathematics and computer science PROSE 05-10-06 2 Overview Workflow (WF) nets and proper termination. Problems with fixed structure of nets especially exception modelling. EWF nets: WF nets with exception transitions. AWF (adaptive WF) nets: nesting. Verification of AWF nets.

3. a 14← department of mathematics and computer science PROSE 05-10-06 3 Workflow net Petri net with initial (source) and final (sink) place. All other nodes on directed path from source to sink. Soundness: every marking reachable from [ i ] can reach [ f ] Marking: e.g. [p]+2[q] i f b a d c p q r Enabled, firing Reachability: ([ i ] sat AG EF [ f ]) Always:

4. a 14← department of mathematics and computer science PROSE 05-10-06 4 Problem: modelling exceptions Typical sound WF net with parallelism (normal flow): i f In one thread an exception may occur. The other thread should be interrupted. Soundness should be preserved. superfluous firing needed Model becomes unfeasible.

5. a 14← department of mathematics and computer science PROSE 05-10-06 5 Reset arcs i f Reset arc empties all places in region. Improves modeling, makes analysis worse. No specific reaction to exceptions. Problem with adaptivity in general, due to fixed structure!

6. a 14← department of mathematics and computer science PROSE 05-10-06 6 EWF nets i f Labelled exception (sink) transitions; upon firing an exception, the net is terminated. EWF net is sound iff

7. a 14← department of mathematics and computer science PROSE 05-10-06 7 AWF nets: definition Adaptive WF (AWF) net: coloured EWF net. Arcs and transitions are labeled with expressions n : an EWF net n final( v ) init( n ) v v e(v)e(v) b b b b b 

8. a 14← department of mathematics and computer science PROSE 05-10-06 8 AWF nets: allowed expressions Out-arc expr’s built from: std nets, variables, operators e.g.:. (seq. composition), + (choice), || (parallel composition) init( n || m ). k In-arc expressions: - b : black, -v (variable): net We presuppose a set of “standard” sound EWF nets (domain dependent). v Transition expressions (guards): - none, - e ( v ) ( e exception  label), - final( v ), final( v )

9. a 14← department of mathematics and computer science PROSE 05-10-06 9 AWF net firing rules AWF net and token net can fire independently m n init( n+m ) v final( v ) v e(v)e(v) b b b b b init  e(v)e(v) v + t Transitions in the AWF net can fire, producing black or net tokens. init+m+m marked net tokens or synchronized on exception label e e or upon token net having reached the final state. final

10. a 14← department of mathematics and computer science PROSE 05-10-06 10 Adaptivity Modeling hospital admission; standard cure n. Monitor; if needed extend current cure with m. e(w)e(w) init( n ) init( c ) vv.m w init( c ) v w final( v )  final( w ) c:c: e: extension needed.

11. a 14← department of mathematics and computer science PROSE 05-10-06 11 Circumspectness AWF net: final( v ) init( n ) v b b b b  b b n:n: Sound, but can not react to exception e in token net n. (not circumspect) AWF net N is circumspect: every exception e of token net can synchronize in any state of N.

12. a 14← department of mathematics and computer science PROSE 05-10-06 12 Circumspect AWF net Net can synchronize with e before and after firing of t. init( n+m ) v final( v ) v e(v)e(v) b b b b b init  e(v)e(v) v m n + t

13. a 14← department of mathematics and computer science PROSE 05-10-06 13 Verification of AWF nets Colour sets of AWF nets are infinite, so no direct model checking possible. v. m v Abstract interpretation  : map token colours to sets of exception labels. Theorem: AWF net N sound iff all states reachable in  ( N ) by nonexceptional firings can terminate without synchronising on exceptions. The set of library net exception labels is finite! Similar result for circumspectness.

14. a 14← department of mathematics and computer science PROSE 05-10-06 14 Conclusions EWF nets: WF nets with exceptions. AWF nets: EWF nets with nesting (e.g. reaction to exceptions). Proper termination and circumspectness of AWF nets can be checked. Extensions: Synchronisation without termination. Checking other temporal properties. Thank you for your attention! department of mathematics and computer science