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JOpera visual web service composition tool

The JOpera visual service composition environment is an advanced workflow definition tool that has been augmented with innovative execution monitoring and debugging capabilities. A workflow process is composed of a set of service invocations (or tasks) and its structure defines the control and data flow dependencies between them. Following this approach, it becomes possible to give a high-level description over the partial order of invocation of the services and their interactions while maintaining well-defined, executable semantics.

With this tool, a process can be modelled with different syntaxes. Developers of the composition may use a visual representation to draw the interactions between the services that should be composed. However, in order to facilitate the development and the interoperability of the various tools (e.g., editors, model checkers, compilers, monitoring tools) composite service definitions are stored behind the scenes using the XML syntax.

As previously mentioned, the tool can be used to manage the entire lifecycle of a process. This begins with the service library, where web services can be imported as reusable components. The developer can browse the library, select a set of basic services and drag and drop them into a process. Then, he or she may begin to define their interactions by drawing the data flow graph. This operation is partially automatic, since the Adapt visual composition editor can bind parameters with matching names. Manual intervention is only required to resolve ambiguities and connect parameters that could not be automatically matched. To get an overview over the order of execution of the tasks and add additional constraints, the user may view and edit the control flow graph. The visual editor automatically keeps the two graphs synchronized and provides advanced model checking facilities that can be used to validate the composition.

At runtime, the visual representation is augmented with colour-coded information representing the current state of the execution of the tasks and developers can click on parameters to inspect their current value. The tool also features capabilities to administer the set of deployed processes and control their overall execution. If failures occur, it highlights them so that the debugging facilities can be applied to interactively determine the cause of the problem.

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