Petrifying Operating Guidelines for Web Services
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The document proposes an approach to implicitly represent operating guidelines for web services using Petri nets and Boolean annotations to address the state space explosion problem. It represents the operating guidelines as a Petri net structure along with two sets - S and F - to track states. This achieves a complexity reduction from quadratic to linear compared to the original approach. It further optimizes the representation by partitioning S and minimizing F based on structural properties of the Petri net.
![Observations about Annotations I Negation does not occur, just conjunction and disjunction Only labels of leaving transitions occur in annotation If node has send successor (!x), it occurs in every clause annotations w.r.t. send events can be inferred from structure final does not occur in same clause with receive messages alternative representation of annotation: !x 1 ⋁... ⋁ !x m ⋁ [final ⋀] (?y 11 ⋁... ⋁ ?y 1k 1 ) ⋀... ⋀ (?y 1n ⋁... ⋁ ?y 1k n ) !a !a !a !a !a !a !i !i !i !o !o ?r ?r ?a ?a !i ⋁ !o !i ⋁ (?a ⋀ ?r) !i !o ?a ⋀ ?r final](https://image.slidesharecdn.com/acsd2009b-090914054309-phpapp02/85/Petrifying-Operating-Guidelines-for-Web-Services-6-320.jpg)
![Observations about Annotations II !x 1 ⋁... ⋁ !x m ⋁ [final ⋀] (?y 11 ⋁... ⋁ y 1k 1 ) ⋀... ⋀ (?y 1n ⋁... ⋁ ?y 1k n ) Forward propagation of receive clauses Backward propagation of receive clauses (?a ⋁ remaining clause) ⋀ X ⇒ (?a ⋁ remaining clause) ⋀ X ... ( remaining clause) ⋀ Y ?a ?a ?a (clause) ⋀ X ⇒ ?a (clause) ⋀ X (?a ⋁ clause) ⋀ Y](https://image.slidesharecdn.com/acsd2009b-090914054309-phpapp02/85/Petrifying-Operating-Guidelines-for-Web-Services-7-320.jpg)
![Implicit representation of annotations Let F = set of states where final occurs in annotation Let S = set of states where only send events occur in some clause Original annotations can be reconstructed: !x 1 ⋁... ⋁ !x m ⋁ [final ⋀] (?y 11 ⋁... ⋁ y 1k 1 ) ⋀... ⋀ (?y 1n ⋁... ⋁ ?y 1k n ) from structure from set F some path to S ⋃F some path to S ⋃F](https://image.slidesharecdn.com/acsd2009b-090914054309-phpapp02/85/Petrifying-Operating-Guidelines-for-Web-Services-8-320.jpg)
Petrifying Operating Guidelines for Web Services
- 1. Petrifying Operating Guidelines for Web Services Niels Lohmann, Karsten Wolf Universität Rostock
- 2. Intro: Operating Guidelines Correctness criterion: no deadlocks, no livelocks, no message overflow Simplified approach: !a ?b ?c !a ?b ?d !a !a !a !a (!a ⋁ ?b ⋁ ?c) ⋀ (!a ⋁ ?b) ⋀ (!a ⋁ ?d ⋁ final) Operating guidelines = Most permissive partner + Boolean annotations Find = Find simulation relation + Evaluate annotations
- 3. Example ? o ffer ! r eject ! a ccept ? i nvoice customer service !i !i !i !o !o ?r ?r ?a ?a !i ⋁ !o !i ⋁ (?a ⋀ ?r) !i !o ?a ⋀ ?r final operating guidelines !o ?r !i ?a partner !o ?r !i !i no partner (simulation) !o !i ?a no partner (annotation) ?r
- 4. Applications Discovery in SOA Service validation Substitutability of services Test case selection Instance migration Service composition ...
- 5. Size of Operating Guidelines Problem: How to deal with the formulas? Size Petri net Size automaton Name 167 77056 Quotation requisition 65 9472 Passport application 93 7792 Deliver finished goods 116 5760 Contract Negotiation 94 1866 Reservations 76 992 Purchase order 95 776 Travel service 249 692 Internal order 316 484 Online shop 116 403 Ticket reservation
- 6. Observations about Annotations I Negation does not occur, just conjunction and disjunction Only labels of leaving transitions occur in annotation If node has send successor (!x), it occurs in every clause annotations w.r.t. send events can be inferred from structure final does not occur in same clause with receive messages alternative representation of annotation: !x 1 ⋁... ⋁ !x m ⋁ [final ⋀] (?y 11 ⋁... ⋁ ?y 1k 1 ) ⋀... ⋀ (?y 1n ⋁... ⋁ ?y 1k n ) !a !a !a !a !a !a !i !i !i !o !o ?r ?r ?a ?a !i ⋁ !o !i ⋁ (?a ⋀ ?r) !i !o ?a ⋀ ?r final
- 7. Observations about Annotations II !x 1 ⋁... ⋁ !x m ⋁ [final ⋀] (?y 11 ⋁... ⋁ y 1k 1 ) ⋀... ⋀ (?y 1n ⋁... ⋁ ?y 1k n ) Forward propagation of receive clauses Backward propagation of receive clauses (?a ⋁ remaining clause) ⋀ X ⇒ (?a ⋁ remaining clause) ⋀ X ... ( remaining clause) ⋀ Y ?a ?a ?a (clause) ⋀ X ⇒ ?a (clause) ⋀ X (?a ⋁ clause) ⋀ Y
- 8. Implicit representation of annotations Let F = set of states where final occurs in annotation Let S = set of states where only send events occur in some clause Original annotations can be reconstructed: !x 1 ⋁... ⋁ !x m ⋁ [final ⋀] (?y 11 ⋁... ⋁ y 1k 1 ) ⋀... ⋀ (?y 1n ⋁... ⋁ ?y 1k n ) from structure from set F some path to S ⋃F some path to S ⋃F
- 9. Example I !i !i !i !o !o ?r ?r ?a ?a S S S F new annotation !i !i !i !o !o ?r ?r ?a ?a !i ⋁ !o !i ⋁ ( ?a ⋀ ?r ) !i !o ?a ⋀ ?r final old annotation
- 10. Example II S F F S F !x !y !z ?c ?a ?b ?a ?b !x !z ⋁ final final !y final !x !y !z ?c ?a ?b ?a ?b ?c ⋀ ( ?a ⋁ ?b ) ?a ?b
- 11. Matching S F F S F !x !y !z ?c ?a ?b ?a ?b !x-successor sufficient !z-successor sufficient final ok !y-successor sufficient F !x !y !z ?c ?b ?a no ?a-path to S ⋃F no fail clause final ok no Ø -path to S ⋃F no fail clause
- 12. Achieved so far Complexity gain (size of operating guidelines) Old approach: O (|P||R|) New approach: O (|R|) No significant efficiency loss in matching Petri net representation of structure + 2 lists of markings (S,F) Remaining problem: How to represent S,F Boolean predicate BDD Explicit
- 13. Size of Sets S and F 255 3 18 26 3 16 47 7 11 8 #S #F #Formulae Name 1 11264 Quotation requisition 1 1536 Passport application 2 1376 Deliver finished goods 2 1152 Contract Negotiation 6 369 Reservations 1 232 Purchase order 2 192 Travel service 8 184 Internal order 21 153 Online shop 2 110 Ticket reservation
- 14. Further reduction in S and F State without successor must be in F State is never in both S and F State without receiving events is seldom outside S State with receiving events is seldom in S F‘ = F \ states without successors S 1 = S ⋂ states with receiving events S 2 = states without receiving events \ (S ⋃ F) F = F‘ ⋃ states without successors S = S1 ⋃ ( states without receiving events \S2)
- 15. Size of Sets S1, S2, and F‘ 1 1 2 2 6 1 2 8 21 2 #F 0 0 1 0 1 0 0 1 0 0 #S1 0 0 0 0 0 0 0 0 0 0 #S2 255 3 18 26 3 16 47 7 11 8 #S #F‘ Name 0 Quotation requisition 0 Passport application 1 Deliver finished goods 0 Contract Negotiation 5 Reservations 0 Purchase order 1 Travel service 4 Internal order 7 Online shop 1 Ticket reservation
- 16. Conclusion Implicit representation of annotations saves space enables Petri net representation of structure can be stored explicitly Further application in subsitutability checking S1 can be substituted by S2 iff Partners(S1) ⊆ Partners(S2) ... iff simulation between S1 and S2 and implication between related annotations holds ... iff simple local correlation between S- and F-status of related states Size of resulting Petri net could be reduced by injecting unreachable states (recorded in a third set)