Dagstuhl Seminar "The Role of Business Processes in Service-Oriented Architectures"

1. Controllability: A soundness criterion for services Karsten Wolf Universität Rostock, Germany

2. Service Workflow Workflow net   + Interface = Service open Workflow net  

3. Wellformedness Workflow nets: Soundness - always possible to reach end state - every transition reachable open Workflow nets: There exist partner(s) such that - always possible to reach end state (Controllability) - every transition reachable (Transition covering) strategy, covering strategy

4. Setting I: Centralized strategy - A single partner connected to all interface places such that ...   ?

5. Setting II: Decentralized Strategy …with respect to given partition into ports - A family of one partner per port such that.... ? ?  

7. Deciding centralized controllability Step 1: upper approximation of partner behaviour (  ,-) € C T B      oWFN can move partner can move both can move end state deadlock !€ !C !T (  ,C) (  ,€) , (  ,-) (  ,T) !T !€ (  ,CT) (  ,C€),(  ,C),(  ,-) , (  ,B) !€ ?B !T !C !T !C !€ ?B !C (  ,T€),(  ,T),(  ,-) , (  ,B) (  ,-) (  ,C€T),(  ,CT),(  ,T),(  ,C), (  ,T) (  ,C)

8. Deciding centralized controllability Step 2: remove bad states (  ,-) !T !€ (  ,CT) (  ,C€),(  ,C),(  ,-) , (  ,B) ?B !C !T !C !€ ?B (  ,T€),(  ,T),(  ,-) , (  ,B) (  ,-) € C T B      oWFN can move partner can move both can move end state deadlock !€ !C !T (  ,C) (  ,€) , (  ,-) (  ,T) !€ !T !C (  ,C€T),(  ,CT),(  ,T),(  ,C), (  ,T) (  ,C)

9. Deciding centralized controllability Step 3: iterate (  ,-) !€ (  ,C€),(  ,C),(  ,-) , (  ,B) ?B !C !T !€ ?B (  ,T€),(  ,T),(  ,-) , (  ,B) (  ,-) € C T B      oWFN can move partner can move both can move end state deadlock !€ !C !T (  ,C) (  ,€) , (  ,-) (  ,T) !T (  ,CT) !C

10. Deciding centralized controllability Step 4: (optional): construct oWFN (  ,-) !€ (  ,C€),(  ,C),(  ,-) , (  ,B) ?B !C !T !€ ?B (  ,T€),(  ,T),(  ,-) , (  ,B) (  ,-) € C T B      !€ !C !T (  ,C) (  ,€) , (  ,-) (  ,T) € C T B

12. Decentralized controllability traced back to centralized case: C 1 ... C n  C 1 || ... || C n Approach: as centralized case, but remove - bad states - states where actions belonging to different parties are not commutative Algorithm is nondeterministic

13. Example a b   !b !a !a 1. !b 2.

15. Autonomous controllability a b  ? not autonomously controllable