Information Technology Reference
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Fig. 1 Service development
life-cycle [ 9]
Planning
Analysis
&
Design
Conformance
validation
Evolution for
change,
maintenance
Physical design
Execution
&
Monitoring
Construction
&
Testing
Deployment
Provisioning
service deployment and needs to be included in the design phases to guarantee that
services are provided according to the requirements also in variable contexts of exe-
cution and number of requests. In addition, already in the initial design phases there
is a focus on specifying and guaranteeing both functionalities and also the quality
of services, and therefore the analysis and logical design phase are followed by a
conformance validation phase. Monitoring is essential to guarantee the promised
services quality characteristics, but also for evaluating, in the evolution for change
phase, whether a service must evolve iterating the design cycle to better guaran-
tee its quality of service, published in service registries and agreed with service
consumers [ 4] .
In this chapter, we focus on designing services as service compositions. A ser-
vice composition is a set of services which are executed according to a number of
constraints associated to them. Flexibility during the execution is one of the main
characteristics of service compositions.
Most methodological approaches focus on defining an order of execution for
services in the service composition, thus creating executable business processes.
Service orientation however presents some peculiar characteristics that are funda-
mental parts of its innovative approach: on one hand, the service composition is not
necessarily following a fixed predefined process schema, on the other hand some
process characteristics related to the global quality of the service provided by the
composed process become important. The quality of service of the process becomes
one of its characteristics and the goal of the service provider is to guarantee that the
service composition satisfies the promised quality constraints. The service-oriented
approach, in order to reach this goal, takes into consideration another important
aspect, which distinguishes service compositions from traditional workflow-based
processes: the actual services composing the process may vary in different pro-
cess executions, and also during each of the single executions of the process.
In fact, in the literature, there is a distinction between abstract services , which
 
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