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data types mainly in functional aspects, that is, businessEntity,
businessService, bindingTemplate, and tModel. We extend the
UDDI data model with Web service quality information and
encapsulate QoS information following a uniform template formal-
ized by the Extensible Markup Language (XML) Schema definition
in [133]. Since QoS metadata in XML format can be sent to UDDI
through Simple Object Access Protocol (SOAP), the new UDDI
registry can provide a service configuration manager with both the
function and the QoS attributes of the Web services.
Configuration Stage
. The Web service user inputs the function and
QoS requirement to the service configuration manager. In the case
study of sales management service configuration, the salesman may
require the function of recording details of the order, checking the
credit of the customers, delivering the goods, and so on. The relative
importance of different QoS attributes reflecting user subjective
preference or perception is also provided, for example, the weight
for cost and availability are 0.2 and 0.8, respectively. First, accord-
ing to the functional requirement, the service configuration planner
automatically selects services based on whether they meet the
configuration's structural constraints and match interfaces. An
SC-net corresponding to the configuration is built. The service
configuration planner may check the potential problems due to
missing services and unsatisfied interfaces. Second, the service
configuration optimizer obtains the QoS requirement from the user
and accesses to QoS metadata about services from the extended
UDDI data model. The QoS aggregation function is computed.
Through the association algorithm defined earlier, a linear pro-
gramming problem is specified. Finally, the service configuration
optimizer finds the optimal configuration. Sensitivity analysis can
also be performed afterwards.
We adopt the
Spring Framework
[134] for the implementation
of a service configuration planner. The components in a module are
created and wired by using dependency injection capabilities from
Spring Framework
. Access methods and protocols, for example,
SOAP, can be adopted to specify the binding information that
describes how services can be accessed and referenced. The service
configuration optimizer is implemented by a linear programming
solver based on the simplex algorithm.
