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

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

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

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

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

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

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

I1I1 P1P1 I2I2 P3P3 P2P2 P4P4 I1I1 I2I2 P2P2

I1I1 P1P1 I2I2 P3P3 P4P4 P2P2 P4P4 P2P2

P1P1 I2I2 P3P3 P4P4 P2P2 I1I1

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

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

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

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

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

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

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

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

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

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

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

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

Performance notes get_forks release_forks transfer Coordinations per second Our proposal ad-hoc implementation get_forksrelease_forkstransfer

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

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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