1. Universidad de Sevilla An Enablement Detection Algorithm for Open Multiparty Interactions José Antonio Pérez Castellanos

2. Contents n Our objectives n Static multiparty interaction models n Our proposal n Implementation n Performance notes n Conclusions

3. Contents n Our objectives n Static multiparty interaction models n Our proposal n Implementation n Performance notes n Conclusions

4. Our Ojectives To devise a high-level coordination model that… n Allows us to express coordination amongst an arbitrary number of entities n Is able to coordinate entities that do not need to know each another n Can be efficiently implemented

5. Contents n Our objectives n Static multiparty interaction models n Our proposal n Implementation n Performance notes n Conclusions

6. Static Multiparty Interaction Models n Interaction= shared event amongst a set of entities n The occurrence of an interaction is an atomic event n An entity cannot engage in more that one interaction simultaneously

7. States of an interaction Disabled Synchronisation Enabled enablement refusementselection Enablement=each entity is willing to participate in the interaction If some interactions share some entity, only one of them will be able to execute! When synchronisation is achieved, communication can occur by means of slots After execution, interaction becomes disabled. Static Multiparty Interaction Models

8. I1I1 P1P1 I2I2 P3P3 P2P2 P4P4 I1I1 I2I2 P2P2

9. I1I1 P1P1 I2I2 P3P3 P4P4 P2P2 P4P4 P2P2

10. P1P1 I2I2 P3P3 P4P4 P2P2 I1I1

11. n Have efficient, reliable implementations, but… n They are not suitable for open environments These models…

12. Contents n Our objectives n Static multiparty interaction models n Our proposal n Implementation n Performance notes n Conclusions

13. Our Proposal Open multiparty interaction model: n Entities do not need to know each other beforehand n Entities offer to participate in an interaction playing a role n They can put restrictions on what entities should play other roles

14. P2P2 R1R1 S1S1 Q1Q1 I1I1 P Q R I2I2 QS P1P1 S2S2 I’d like that R be played by R 1 I don’t care at all... I wish P1 to play role P I’d like P 1 to play role P, and R 1 to play role R! I’d like... Our Proposal

15. Advantages: n Entities do not need to know each other beforehand: suitable for open environments n Achieves a good level of expressiveness n Can also be efficiently implemented

16. Contents n Our objectives n Static multiparty interaction models n Our proposal n Implementation n Performance notes n Conclusions

17. Implementation n Principle: –Deal with enablement detection separately from enablement selection –Once an enablement has been found, it can be managed as a static interaction amongst the entities involved in it

18. P2P2 R1R1 S1S1 Q1Q1 I1I1 P Q R I2I2 QS P1P1 S2S2 R!R 1 ;Q!Q 1 R!R 2 ;Q!Q 1 Q!Q 1  -solver: enablement detection Implementation

19. R1R1 S1S1 Q1Q1 I 1(a) I 2(b) P1P1 S2S2 Each enablement is dealt with as a static interaction I 2(a)  -core: selects as many non-conflicting interactions (or enablements) as possible I 2(b) S1S1 Q1Q1 Implementation

20. n Main ideas: –Participation offers are represented as tuples: –A binary operation  is defined on tuples, such that: – Operation  is defined iff both offers are compatible – The resulting tuple gathers the information of its operands –We can algorithmically build an acyclic directed graph by successive applications of the operation  I P Q R P1P1 Q!Q 1 [P1, (Q1), ()] [(P 1 ), (Q 1 ), R 1 ]  [P 1, (Q 1 ), R 1 ] Implementation  -solver

21. n Main ideas (to appear in Coordination’02) : –To execute an enablement it must achieve exclusion on all its participants –Participants in more than one enablement are considered as a shared resource amongst them –Enablements must compete in order to get exclusion on their shared participants –To avoid deadlocks: – Exclusion is requested in a given order, locking participants. – When an enablement is refused, it releases all the participants that it locked Implementation  -core

22. Contents n Our objectives n Static multiparty interaction models n Our proposal n Implementation n Performance notes n Conclusions

23. Performance notes get_forks release_forks transfer 0 20 40 60 80 100 120 Coordinations per second Our proposal 85 70 ad-hoc implementation 104 98 get_forksrelease_forkstransfer

24. Presentation Index n Our objectives n Static multiparty interaction models n Our proposal n Implementation n Performance notes n Conclusions

25. Conclusions n Contributions: à A simple, expressive interaction model and à An efficient, reliable implementation n Applications: à Multiorganisational web based systems à E-commerce à Describing behaviours as an aspect: CAL à …

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