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Model aware execution of composite web servicesZurowska, Karolina 15 August 2008
In the Service Oriented Architecture (SOA) services are computational elements that are published, discovered, consumed and aggregated across platform and organizational borders. The most commonly used technology to achieve SOA are Web Services (WSs). This is due to standardization process (WSDL, SOAP, UDDI standards) and a wide range of available infrastructure and tools. A very interesting aspect of WSs is their composeability. WSs can be easily aggregated into complex workflows, called Composite Web Services (CWSs). These compositions of services enable further reuse and in this way new, even more complex, systems are built.<p>Although there are many languages to specify or implement workflows, in the service-oriented systems BPEL (Business Process Execution Language) is widely accepted. With this language WSs are orchestrated and then executed with specialized engines (like ActiveBPEL). While being very popular, BPEL has certain limitations in monitoring and optimizing executions of CWSs. It is very hard with this language to adapt CWSs to changes in the performance of used WSs, and also to select the optimal way to execute a CWS. <p>To overcome the limitations of BPEL, I present a model-aware approach to execute CWSs. To achieve the model awareness the Coloured Petri Nets (CPN) formalism is considered as the basis of the execution of CWSs. This is different than other works in using formal methods in CWSs, which are restricted to purposes like verification or checking of correctness. Here the formal and unambiguous notation of the CPN is used to model, analyze, execute and monitor CWSs. Furthermore this approach to execute CWSs, which is based on the CPN formalism, is implemented in the model-aware middleware. It is also demonstrated how the middleware improves the performance and reliability of CWSs.
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Model aware execution of composite web servicesZurowska, Karolina 15 August 2008 (has links)
In the Service Oriented Architecture (SOA) services are computational elements that are published, discovered, consumed and aggregated across platform and organizational borders. The most commonly used technology to achieve SOA are Web Services (WSs). This is due to standardization process (WSDL, SOAP, UDDI standards) and a wide range of available infrastructure and tools. A very interesting aspect of WSs is their composeability. WSs can be easily aggregated into complex workflows, called Composite Web Services (CWSs). These compositions of services enable further reuse and in this way new, even more complex, systems are built.<p>Although there are many languages to specify or implement workflows, in the service-oriented systems BPEL (Business Process Execution Language) is widely accepted. With this language WSs are orchestrated and then executed with specialized engines (like ActiveBPEL). While being very popular, BPEL has certain limitations in monitoring and optimizing executions of CWSs. It is very hard with this language to adapt CWSs to changes in the performance of used WSs, and also to select the optimal way to execute a CWS. <p>To overcome the limitations of BPEL, I present a model-aware approach to execute CWSs. To achieve the model awareness the Coloured Petri Nets (CPN) formalism is considered as the basis of the execution of CWSs. This is different than other works in using formal methods in CWSs, which are restricted to purposes like verification or checking of correctness. Here the formal and unambiguous notation of the CPN is used to model, analyze, execute and monitor CWSs. Furthermore this approach to execute CWSs, which is based on the CPN formalism, is implemented in the model-aware middleware. It is also demonstrated how the middleware improves the performance and reliability of CWSs.
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A Monolithic Approach To Automated Composition Of Semantic Web Services With The Event CalculusOkutan, Cagla 01 September 2009 (has links) (PDF)
In this thesis, a web service composition and execution framework is presented for semantically
annotated web services. A monolithic approach to automated web service composition
and execution problem is chosen, which provides some benefits by separating the composition
and execution phases. An AI planning method using a logical formalism called Event
Calculus is chosen for the composition phase. This formalism allows one to generate a narrative
of actions and temporal orderings using abductive planning techniques given a goal.
Functional properties of services, namely input/output/precondition/effects(IOPE) are taken
into consideration in the composition phase and non-functional properties, namely quality of
service (QoS) parameters are used in selecting the most appropriate solution to be executed.
The repository of OWL-S semanticWeb services are translated to Event Calculus axioms and
the resulting plans found by the Abductive Event Calculus Planner are converted to graphs.
These graphs can be sorted according to a score calculated using the defined quality of service
parameters of the atomic services in the composition to determine the optimal solution. The
selected graph is converted to an OWL-S file which is executed consequently.
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