Database Reference
In-Depth Information
presented as a content-based routing, sometimes based on rules handled by the rule en-
gine; static routing tables are also common.
This concludes the mapping of synchronous service activities to the technology standards
and
WS-*
specifications.
Asynchronous services are more complex, as more infrastructural technical elements are
required as follows:
• Asynchronous queuing will require server resources such as topics and/or queues
• State repository will be required for resource hibernation during the composition's
inactive state
Their realization is not covered by any particular
WS-*
specification, but their presence is
significant for the
WS-BusinessActivity
specification's implementation. The
WS-
BusinessActivity
specification together with
WS-AtomicTransaction
and
support from
WS-Coordination
has presented the mechanism controlling service
activities over a long period of time. The
Business Activity
coordination protocol can be
perceived as a chain of discrete over-the-time atomic coordinations. As it is clear from the
context, rollback actions are virtually impossible between different stages of business
activities, so the possibility to have an arbitrary compensative transaction is the essential
part of this protocol. Using compensation, it is possible to return the data of an applica-
tion's participant to a consistent state, but not exactly to the state before the transaction,
such as the Atomic Coordination. The complexity of compensative transactions could be
very high, allowing you to correct the changes happened many steps before the actual er-
ror.
Further implementation of standards and recommendations in the right lane is similar to
implementing complex synchronous activities; this confirms the fact that an asynchronous
business activity is a chain of complex synchronous activities. A special significance of
asynchronous transactions is that it has a
WS-Coordination
specification for its role
of establishing a coordinator service model we mentioned earlier.
The composition of a coordinator service model consists of the following services:
• The activation service, which creates new coordination contexts and associates
them with the planning activity
• The registration service, which registers a service's participant and distributes co-
ordination contexts among them
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