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update(factnew);
update(factold
factnew).
More complex transition rules are defined recursively, analogously to classical
ASMs, by “if-then”, “forall” and “choose” rules:
if Condition then Rules endIf
forall Variables with Condition do Rules endForall
choose Variables with Condition do Rules endChoose
Orchestration
Orchestration describes how a service makes use of other services in order to
achieve its capability. In many real scenarios, a service is provided by using
and interacting with services provided by other applications or businesses.
For example, the booking of a trip might involve the use of another service
for validating a credit card and charging it with the correspondent amount,
and the user of the booking service may want to know which other business
organizations they are implicitly going to deal with.
WSMO introduces the orchestration element into the description of a ser-
vice to reflect such dependencies. WSMO orchestration allows the use of stat-
ically or dynamically selected services. In the former case, a concrete service
will be selected at design time. In the latter case, the service will only describe
the goal that has to be fulfilled in order to provide the service. This goal will
be used to select at runtime an available service that fulfills it, and the service
user could influence this choice.
It is envisioned that orchestration should make use of the multiagent asyn-
chronous ASM model to describe the interactions between Web services and
goals. These aspects are still to be investigated further, and will be defined in
future publications.
6.3 Goals
Goals are used in WSMO to describe a user's desires. They provide the means
to specify the requester-side objectives when a Web service is consulted, de-
scribing at a high level a concrete task to be achieved.
Goals are representations of objectives for which fulfillment is sought
through the execution of Web services. They can be descriptions of services
that would potentially satisfy the user's desires.
Note that WSMO completely decouples the objectives that a requester
has, i.e. his/her goal, from the services that can actually fulfill such a goal.
Specified more formally in MOF, a goal is made up of the following elements:
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