164,851 research outputs found
A theory of contracts for web services
<p>Contracts are behavioural descriptions of Web services. We devise a theory of contracts that formalises the compatibility of a client to a service, and the safe replacement of a service with another service. The use of contracts statically ensures the successful completion of every possible interaction between compatible clients and services.</p>
<p>The technical device that underlies the theory is the definition of filters, which are explicit coercions that prevent some possible behaviours of services and, in doing so, they make services compatible with different usage scenarios. We show that filters can be seen as proofs of a sound and complete subcontracting deduction system which simultaneously refines and extends Hennessy's classical axiomatisation of the must testing preorder. The relation is decidable and the decision algorithm is obtained via a cut-elimination process that proves the coherence of subcontracting as a logical system.</p>
<p>Despite the richness of the technical development, the resulting approach is based on simple ideas and basic intuitions. Remarkably, its application is mostly independent of the language used to program the services or the clients. We also outline the possible practical impact of such a work and the perspectives of future research it opens.</p>
Semantic web service choreography: contracting and enactment
Abstract. The emerging paradigm of service-oriented computing requires novel techniques for various service-related tasks. Along with automated support for service discovery, selection, negotiation, and composition, support for automated service contracting and enactment is crucial for any large scale service environment, where large numbers of clients and service providers interact. Many problems in this area involve reasoning, and a number of logic-based methods to handle these problems have emerged in the field of Semantic Web Services. In this paper, we build upon our previous work where we used Concurrent Transaction Logic (CTR) to model and reason about service contracts. We significantly extend the modeling power of the previous work by allowing iterative processes in the specification of service contracts, and we extend the proof theory of CTR to enable reasoning about such contracts. With this extension, our logic-based approach is capable of modeling general services represented using languages such as WS-BPEL
Contract Aware Components, 10 years after
The notion of contract aware components has been published roughly ten years
ago and is now becoming mainstream in several fields where the usage of
software components is seen as critical. The goal of this paper is to survey
domains such as Embedded Systems or Service Oriented Architecture where the
notion of contract aware components has been influential. For each of these
domains we briefly describe what has been done with this idea and we discuss
the remaining challenges.Comment: In Proceedings WCSI 2010, arXiv:1010.233
Preliminary Results Towards Contract Monitorability
This paper discusses preliminary investigations on the monitorability of
contracts for web service descriptions. There are settings where servers do not
guarantee statically whether they satisfy some specified contract, which forces
the client (i.e., the entity interacting with the server) to perform dynamic
checks. This scenario may be viewed as an instance of Runtime Verification,
where a pertinent question is whether contracts can be monitored for adequately
at runtime, otherwise stated as the monitorability of contracts. We consider a
simple language of finitary contracts describing both clients and servers, and
develop a formal framework that describes server contract monitoring. We define
monitor properties that potentially contribute towards a comprehensive notion
of contract monitorability and show that our simple contract language satisfies
these properties.Comment: In Proceedings PrePost 2016, arXiv:1605.0809
Contract agreements via logic
We relate two contract models: one based on event structures and game theory,
and the other one based on logic. In particular, we show that the notions of
agreement and winning strategies in the game-theoretic model are related to
that of provability in the logical model.Comment: In Proceedings ICE 2013, arXiv:1310.401
Loosening the notions of compliance and sub-behaviour in client/server systems
In the context of "session behaviors" for client/server systems, we propose a
weakening of the compliance and sub-behaviour relations where the bias toward
the client (whose "requests" must be satisfied) is pushed further with respect
to the usual definitions, by admitting that "not needed" output actions from
the server side can be "skipped" by the client. Both compliance and
sub-behaviour relations resulting from this weakening remain decidable, though
the proof of the duals-as-minima property for servers, on which the
decidability of the sub-behaviour relation relies, requires a tighter analysis
of client/server interactions.Comment: In Proceedings ICE 2014, arXiv:1410.701
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