1 / 21

Controllability: A soundness criterion for services

Controllability: A soundness criterion for services. Karsten Wolf Universität Rostock, Germany. . open Workflow net. . Service. . Workflow. Workflow net. . + Interface = Service. strategy, covering strategy. Wellformedness.

zena
Download Presentation

Controllability: A soundness criterion for services

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

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

  2. open Workflow net  Service  Workflow Workflow net  + Interface = Service Karsten Wolf: Controllability...

  3. strategy, covering strategy 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) Karsten Wolf: Controllability...

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

  5.  Setting II: Decentralized Strategy…with respect to given partition into ports - A family of one partner per portsuch that.... ? ? Karsten Wolf: Controllability...

  6.  Setting III: Autonomous Strategy • Independently built partners for all ports ? Karsten Wolf: Controllability...

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

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

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

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

  11. Centralized controllability: results • oWFN controllable if and only if construction yields nonempty structure • Constructed partner is most permissive • Transition covering can be decided • Basis for characterization of all strategies = operating guideline • State explosion  Reduction techniques, symbolic representations Karsten Wolf: Controllability...

  12. Decentralized controllability traced back to centralized case: C1 ... Cn C1 || ... || Cn Approach: as centralized case, but remove - bad states - states where actions belonging to different parties are not commutative Algorithm is nondeterministic Karsten Wolf: Controllability...

  13. !a 1. !a !b !b 2. Example a b a w Karsten Wolf: Controllability...

  14. Decentralized controllability: results • There is no unique most permissive decentralized strategy • Nevertheless, a set of strategies covering all others can be computed  transition covering decidable Karsten Wolf: Controllability...

  15. Autonomous controllability a ? b a not autonomously controllable Karsten Wolf: Controllability...

  16. Autonomous controllability Idea: set of rules for cooperation s.t. : if everyone obeys rules, system behaves well Autonomous controllability = for each port, there exists a cooperative partner Karsten Wolf: Controllability...

  17. a a b b a a w w Rules for cooperation 1. Behave like a centralized strategy pretending that communication with other parties were internal a a w 2. If only receive transitions are activated in inner oWFN, including one for your part of interface, provide an action (impossible in this example) Karsten Wolf: Controllability...

  18. Results: Autonomous controllability • Thm: Every family of cooperative partners is a decentralized strategy • Algorithm for cooperative partners similar to centralized case • For each port, there is a unique most permissive cooperative partner ( transition covering) Karsten Wolf: Controllability...

  19. Relations between settings • Autonomous controllability implies decentralized controllability • Decentralized controllability implies centralized controllability • In special decentralized case with only one party, all three concepts coincide Karsten Wolf: Controllability...

  20. More Settings • Other communication schemes • Synchronous communication • Dependencies between messages (empty form – filled form) • Specific partners, • „I want coffee“ • „I do not want tea“ Karsten Wolf: Controllability...

  21. Related work • Our approach more general than [Martens03] • decentralized, autonomous case • most permissive • Reduction techniques [Weinberg04] • Operating Guidelines [Massuthe,Schmidt05] Karsten Wolf: Controllability...

More Related