@article {jopjauto07,
	title = {Autonomic resource provisioning for software business processes},
	journal = {Information and Software Technology},
	volume = {49},
	year = {2007},
	month = {January},
	pages = {65-80},
	abstract = {Software development nowadays involves several levels of abstraction: starting from the programming of single objects, to their combination into components, to their publication as services and the overall architecture linking elements at each level. As a result, software engineering is dealing with a wider range of artifacts and concepts (i.e., in the context of this paper: services and business processes) than ever before. In this paper we explore the importance of having an adequate engine for executing business processes written as compositions of Web services. The paper shows that, independently of the composition language used, the overall scalability of the system is determined by how the run-time engine treats the process execution. This is particularly relevant at the service level because publishing a process through a Web service interface makes it accessible to an unpredictable and potentially very large number of clients. As a consequence, the process developer is confronted with the difficult question of resource provisioning. Determining the optimal configuration of the distributed engine that runs the process becomes sensitive both to the actual number of clients and to the kinds of processes to be executed. The main contribution of the paper is to show how resource provisioning for software business processes can be solved using autonomic computing techniques. The engine separates execution in two stages (navigation and dispatching) and uses a controller to allocate the node of a cluster of computers to each one of those stages as the workload changes. The controller can be configured with different policies that define how to reconfigure the system. To prove the feasibility of the concept, we have implemented the autonomic controller and evaluated its performance with an extensive set of experiments.},
	keywords = {autonomic computing, distributed business process execution engines, service oriented architectures, Web service composition},
	doi = {10.1016/j.infsof.2006.08.010},
	author = {Cesare Pautasso and Thomas Heinis and Gustavo Alonso}
}
@conference {jopera:2006:scc,
	title = {Control the Flow: How to Safely Compose Streaming Services into Business Processes},
	booktitle = {2006 IEEE International Conference on Services Computing},
	year = {2006},
	pages = {206 - 213},
	publisher = {IEEE},
	organization = {IEEE},
	address = {Chicago, USA},
	abstract = {Although workflow languages are widely used for composing discrete services, these are not suitable for stream based interactions. In this paper we address the problem of how to extend a conventional Web service composition language with the ability to deal with data streaming services. The paper discusses several modeling alternatives and presents a marker based semantics for safely dealing with pipelined processing in service compositions. The paper also presents application examples that illustrate the advantages of the proposed approach},
	keywords = {JOpera, streaming, Web service composition},
	doi = {10.1109/SCC.2006.38},
	author = {Bi{\"o}rn Bi{\"o}rnstad and Cesare Pautasso and Gustavo Alonso}
}
@article {117,
	title = {JOpera: Autonomic Service Orchestration},
	journal = {IEEE Data Engineering Bulletin},
	volume = {29},
	year = {2006},
	month = {September},
	pages = {32-39},
	keywords = {autonomic computing, JOpera, Web service composition},
	url = {ftp://ftp.research.microsoft.com/pub/debull/A06sept/issue1.htm},
	author = {Cesare Pautasso and Thomas Heinis and Gustavo Alonso}
}
@conference {jopera:2005:icws,
	title = {Autonomic Execution of Service Compositions},
	booktitle = {3rd International Conference on Web Services (ICWS 2005)},
	year = {2005},
	month = {July},
	publisher = {IEEE},
	organization = {IEEE},
	address = {Orlando, Florida},
	abstract = {An increasing amount of Web services are being implemented using process management tools and languages (BPML, BPEL, etc.). The main advantage of processes is that designers can express complex business conversations at a high level of abstraction, even reusing standardized business protocols. The downside is that the infrastructure behind the Web service becomes more complex. This is particularly critical for Web services that may be subjected to high variability in demand and suffer from unpredictable peaks of heavy load. In this paper we present a flexible architecture for process execution that has been designed to support autonomic scalability. The system runs on a cluster of computers and reacts to workload variations by altering its configuration in order to optimally use the available resources. Such changes happen automatically and without any human intervention. This feature completely removes the need for the manual monitoring and reconfiguration of the system, which in practice is a difficult and time-consuming operation. In the paper we describe the architecture of the system and present an extensive performance evaluation of its autonomic capabilities.},
	keywords = {autonomic computing, JOpera, Web service composition},
	doi = {10.1109/ICWS.2005.28},
	author = {Cesare Pautasso and Thomas Heinis and Gustavo Alonso}
}
@conference {jopera:2005:icac,
	title = {Design and Evaluation of an Autonomic Workflow Engine},
	booktitle = {2nd International Conference on Autonomic Computing (ICAC-05)},
	year = {2005},
	month = {June},
	pages = {27 - 38},
	publisher = {IEEE},
	organization = {IEEE},
	address = {Seattle, Washington},
	abstract = {In this paper we present the design and evaluate the performance of an autonomic workflow execution engine. Although there exist many distributed workflow engines, in practice, it remains a difficult problem to deploy such systems in an optimal configuration. Furthermore, when facing an unpredictable workload with high variability, manual reconfiguration is not an option. Thanks to its autonomic controller, the engine features self-configuration, self-tuning and self-healing properties. The engine runs on a cluster of computers using a tuple space to coordinate its various components. Its autonomic controller monitors its performance and responds to workload variations by altering the configuration. In case failures occur, the controller can recover the workflow execution state from persistent storage and migrate it to a different node of the cluster. Such interventions are carried out without any human supervision. As part of the results of our performance evaluation, we compare different autonomic control strategies and discuss how they can automatically tune the system},
	keywords = {automatic configuration, autonomic computing, JOpera, Web service composition},
	doi = {10.1109/ICAC.2005.21},
	author = {Thomas Heinis and Cesare Pautasso and Gustavo Alonso}
}
@inproceedings {jopera:2005:sc,
	title = {Flexible Binding for Reusable Composition of Web Services},
	year = {2005},
	month = {April},
	pages = {151-166},
	publisher = {Springer},
	address = {Edinburg, Scotland},
	abstract = {In addition to publishing composite services as reusable services, compositions can also be reused by applying them to orchestrate different component services. To do so, it is important to describe compositions using flexible bindings, which define only the minimal constraints on the syntax and semantics of the services to be composed. This way, the choice of which service to invoke can be delayed to later stages in the life cycle of the composition. In the context of Web service composition, we refine the concept of binding beyond the basic distinction of static and dynamic binding. Bindings can be evaluated during the design, the compilation, the deployment, the beginning of the execution of a composition, or just before the actual service invocation takes place. Considering the current limited support of dynamic binding in the BPEL service composition language, we show how we addressed the problem in JOpera, where modeling bindings does not require a specific language construct as it can be considered a special application of reflection.},
	keywords = {dynamic binding, JOpera, Web service composition},
	doi = {10.1007/11550679_12},
	author = {Cesare Pautasso and Gustavo Alonso}
}
@article {106,
	title = {The JOpera visual composition language},
	journal = {J. Vis. Lang. Comput.},
	volume = {16},
	year = {2005},
	month = {February},
	pages = {119{\textendash}152},
	abstract = {Composing Web services into a coherent application can be a tedious and error-prone task when using traditional textual scripting languages or emerging XML-based approaches. As an alternative, complex interactions patterns and data exchanges between different Web services can be effectively modeled using a visual language. In this paper, we discuss the requirements of such an application scenario and we fully describe the JOpera Visual Composition Language. An extensive set of visual editing tools, a compiler and a debugger for the language have been implemented as part of the JOpera system with the goal of providing a true visual environment for Web service composition with usability features emphasizing rapid development and visual scalability. },
	keywords = {data flow, JOpera, visual composition languages, Web service composition, Web services},
	issn = {1045-926X},
	doi = {10.1016/j.jvlc.2004.08.004},
	author = {Cesare Pautasso and Gustavo Alonso}
}
@article {96,
	title = {JOpera: a Toolkit for Efficient Visual Composition of Web Services},
	journal = {International Journal of Electronic Commerce (IJEC)},
	volume = {9},
	year = {2004},
	month = {Winter 2004/2005},
	pages = {107-141},
	abstract = {Web services are attracting attention because of their ability to provide standard interfaces to heterogeneous distributed services. Standard interfaces make it possible to compose more complex services out of basic ones. This paper tackles the problem of visual service composition and the efficient and scalable execution of the resulting composite services. The effort revolves around the JOpera system, which combines a visual programming environment for Web services with a flexible execution engine that interacts with Web services through the simple object access protocol (SOAP), described with Web services language description (WSDL) and registered with a universal description discovery and integration (UDDI) registry. The paper explains the syntax and implementation of the JOpera Visual Composition Language (JVCL) and its ability to provide different quality of service (QoS) levels in the execution of composite services. },
	keywords = {JOpera, Scalable Process Execution, visual languages, Web service composition},
	issn = {1086-4415 },
	url = {http://www.ijec-web.org/past-issues/volume-9-number-2-winter-2004-05/ijecv9n2-6/},
	author = {Cesare Pautasso and Gustavo Alonso}
}
@conference {94,
	title = {Visual composition of Web services},
	booktitle = {IEEE Symposium on Human Centric Computing Languages and Environments (HCC 2003)},
	year = {2003},
	month = {October},
	pages = {92 - 99},
	publisher = {IEEE},
	organization = {IEEE},
	address = {Auckland, New Zealand},
	abstract = {Composing Web services into a coherent application can be a tedious and error prone task when using traditional textual scripting languages. As an alternative, complex interactions patterns and data exchanges between different Web services can be effectively modeled using a visual language. In this paper we discuss the requirements of such an application scenario and we present the design of the BioOpera Flow Language. This visual composition language has been fully implemented in a development environment for Web service composition with usability features emphasizing rapid development and visual scalability.},
	keywords = {JOpera, visual languages, visual service composition, Web service composition, Web services},
	doi = {10.1109/HCC.2003.1260208},
	url = {http://ieeexplore.ieee.org/lpdocs/epic03/wrapper.htm?arnumber=1260208},
	author = {Cesare Pautasso and Gustavo Alonso}
}
