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Cognitive Science

Composition of Services with Constraints

Profile image of Olga KouchnarenkoOlga Kouchnarenko

2010, Electronic Notes in Theoretical Computer Science

https://doi.org/10.1016/J.ENTCS.2010.05.003
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Abstract

Composition of Web services consists of the interleaving of the sequence of actions executed by the elementary services in accordance with a client specification. We model Web services as automata executing actions and also sending and receiving messages. This paper provides a theoretical study for three service composition problems, and in particular for the problem of computing a Boolean formula which exactly characterises the conditions required for services to answer the client's request. New complexity results are established for these problems within the framework of service composition with constraints.

Figures (6)
Figure 1. Boolean automata A; and Ag. P. Balbiani et al. / Electronic Notes in Theoretical Computer Science 263 (2010) 31-46
Figure 1. Boolean automata A; and Ag. P. Balbiani et al. / Electronic Notes in Theoretical Computer Science 263 (2010) 31-46
P. Balbiani et al. / Electronic Notes in Theoretical Computer Science 263 (2010) 31-46
P. Balbiani et al. / Electronic Notes in Theoretical Computer Science 263 (2010) 31-46
Service 5; provides an on-line booking for European football match places th will take place in Madrid. This service is modeled by the automaton A, in Fig. 4 When S$} receives a request for a football place (ticket_ req) booking, it chec whether there is available places having the desired price (action c_v). This che can be done if and only if the request is provided by a non black listed support (predicate ppiack). If there is no available place, S; informs the requester by t action no_ ticket. If there is a ticket, S, asks the bank service ($3) for the tick payment (actions !ask_bank1). If the bank answers the payment is Ok (messa ?resp_bank1), the ticket is sent to the requester (action send_ticket).
Service 5; provides an on-line booking for European football match places th will take place in Madrid. This service is modeled by the automaton A, in Fig. 4 When S$} receives a request for a football place (ticket_ req) booking, it chec whether there is available places having the desired price (action c_v). This che can be done if and only if the request is provided by a non black listed support (predicate ppiack). If there is no available place, S; informs the requester by t action no_ ticket. If there is a ticket, S, asks the bank service ($3) for the tick payment (actions !ask_bank1). If the bank answers the payment is Ok (messa ?resp_bank1), the ticket is sent to the requester (action send_ticket).
P. Balbiani et al. / Electronic Notes in Theoretical Computer Science 263 (2010) 31-46 S3 accepts request from services having a security certificate (predicate peers; means that S; has such a certificate). Then, if the buyer has either a credit card (predicate pec) or a paypal account (predicate pp»), and if the payment is OK (in order to not overload the example, we do not model this communicating point; we just encode it by the action pay_ok), the bank validates the payment to the related service.
P. Balbiani et al. / Electronic Notes in Theoretical Computer Science 263 (2010) 31-46 S3 accepts request from services having a security certificate (predicate peers; means that S; has such a certificate). Then, if the buyer has either a credit card (predicate pec) or a paypal account (predicate pp»), and if the payment is OK (in order to not overload the example, we do not model this communicating point; we just encode it by the action pay_ok), the bank validates the payment to the related service.
As pointed out by the above table, a still open question is to evaluate the exact com- plexity of the valuation decision problem for ——> and the Boolean formula decision problem for —>: are they in PSPACE or are they EX PTIM E-hard? Moreover. we focused on the identification of a relevant abstraction to manage conditional actions in the service composition problem. In the future, we intend to explore practical algorithmic approaches to handle the Boolean formula synthesis problem.
As pointed out by the above table, a still open question is to evaluate the exact com- plexity of the valuation decision problem for ——> and the Boolean formula decision problem for —>: are they in PSPACE or are they EX PTIM E-hard? Moreover. we focused on the identification of a relevant abstraction to manage conditional actions in the service composition problem. In the future, we intend to explore practical algorithmic approaches to handle the Boolean formula synthesis problem.

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Related topics

  • Cognitive Science
  • Service Composition
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