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2. Update Rule Extension: Calls
3. Conclusions and Further Work
The orchestration of a WSMO service defines how the overall
functionality of the service is achieved by the cooperation of other
services. It describes how the service works from the provider's
perspective (i.e. how a service makes use of other WSMO services or goals in
order to achieve its capability). This complies with the W3C definition of
Web Service Orchestrations [W3C Working Group]:
An orchestration defines the sequence and conditions in which one Web
Service invokes other Web Services in order to realize some useful function.
That is, an orchestration is the pattern of interactions that a Web Service
agent must follow in order to achieve its goal.
As in WSMO Choreography [Roman et al., 2005], the conceptual model of WSMO orchestrations is based on Abstract State Machines [Gurevich, 1995].
In particular WSMO Orchestration descriptions inherit syntax and semantics of the Ontologized Abstract State Machine language from WSMO Orchestration descriptions and extend it with syntactical constructs to invoke services, achieve goals and apply mediators. Due to thecallout
nature of these statements, the semantics are not concretely defined as they are for
instance for an add statement. In the case of achieving a goal the orchestration
delegates the achievement of the goal's functional promise to an external entity and does not
have a priori knowledge of the set of results instances.
Class wsmoOrchestration
hasNonFunctionalProperties type nonFunctionalProperties
hasStateSignature type stateSignature
hasState type state
hasTransitionRules type transitionRules
|
The rest of the document is organized as follows. In Section 2 we describe a new kind of update rule and how they differ from the ones defined in WSMO choreographies and in Section 3 we conclude with some remarks and future work.
forall do, choose do and
if then) which are typically utilized in a similar way as in choreographies to organize the
control flow of an orchestration. We also retain the update rules (add, delete
and udpate) and on top of that we allow another kind of update rule: call.
The meta-model is extented as follows:
Class callOut sub-Class updateRule
hasCallee type {webService, goal, mediator}
|
modifier, fact, iri and irilist are defined in
the choreography syntax and where updaterule is the point where we hook into the syntax)
| updaterule | = |
|
||||||
| callee | = |
|
The call keyword is used for invocation purposes of either a goal, web service or a mediator. As the keyword indicates in all three cases the orchestration delegates execution to an external entity. When the goal in question is achieved, the mediation applied or the service invoked, a set of result instances are reincorporated into the machine state.
This document presented the representation of orchestration in WSMO. It is based on an extension of Ontologized Abstract State Machine as they were defined for choreographies.
[AsmL] Abstract State Machine Language. Available at http://research.microsoft.com/fse/asml/
[Gurevich, 1995]E. Boerger (ed.): Yuri Gurevich:Evolving Algebras 1993: Lipari Guide, Specification and Validation Methods, Oxford University Press, 1995, 9--36.
[Roman et al., 2004] D. Roman, H. Lausen, U. Keller (eds.): Web Service Modelling Ontology (WSMO), WSMO deliverable D2 version 1.1. available at http://www.wsmo.org/2004/d2/v1.1/
[Roman et al., 2005] D. Roman, J. Scicluna (eds.): Choreography in WSMO, WSMO deliverable D14 version 0.1. available at http://www.wsmo.org/2004/d14/v0.1/20041112/
[W3C Working Group] H. Haas, A. Brown (eds.): Web Services Glossary, W3C Working Group Note 11 February 2004 available at http://www.w3.org/TR/2004/NOTE-ws-gloss-20040211/
The work is funded by the European Commission under the projects DIP, Knowledge Web, Ontoweb, SEKT, SWWS, Esperonto, COG and h-TechSight; by Science Foundation Ireland under the DERI-Lion project; and by the Vienna city government under the CoOperate program.
The editors would like to thank to all the members of the WSMO working group for their advice and input into this document.