Adaptive and Distributed Service Oriented Processes: An Architectural Methodology Michael Pantazoglou, George Athanasopoulos, Aphrodite Tsalgatidou

Let us now describe how the structured activity Sequence2 of the landslide BPEL process will be executed based on the results of the recruitment procedure shown in Table 1. In principle, a sequence activity within a BPEL process is responsible for sequentially executing all its child activities. In our example, node 010, which is responsible for the execution of Sequence2, sends an ExecuteActivity request to node 011, and waits until it receives back an ActivityCompleted notification. Node 011 is responsible for the execution of activity Assign1, which is the first child activity of Sequence2.

Since the activity Assign1 is synchronized with activity Assign2 through a BPEL link (see arrow in Figure 5), node 011 will wait until an ActivityCompleted notification is sent from node 001. Then, it sends a ReadVariable request to node 000, in order to retrieve the value of the LandslideInput variable. After that, the node proceeds with the execution of the copy statements within the assign activity, and locally writes the produced outcome to the DEMInput variable. At this point, the Assign1 activity has completed and node 011 sends an ActivityCompleted notification to node 010, which is in charge of the parent activity, Sequence2.

Node 010 resumes the execution of Sequence2, which dictates that the Invoke1 activity is executed next. To do so, an ExecuteActivity request is sent to node 111, which is responsible for that activity. Before performing the actual invocation of the Digital Elevation Model WCS, node 111 retrieves the required input by reading the DEMInput variable from node 011. After invocation, the service output is locally written to variable DEM, and an ActivityCompleted notification is sent back to node 010, allowing it to complete the execution of activity Sequence2, and send the appropriate notification to node 110, which is in charge of the execution of the parent Flow activity.

Discuss future and emerging trends. Provide insight about the future of the book’s theme from the perspective of the chapter focus. Viability of a paradigm, model, implementation issues of proposed programs, etc., may be included in this section. If appropriate, suggest future research opportunities within the domain of the topic.

The results of this work could be extended and/or improved in numerous ways. The implementation of a WPS interface on top of the Adaptive Execution Infrastructure will render it more aligned to the ongoing developments in the environmental domain. Support for data provenance, as well as the provision of efficient big-data transferring mechanisms would further enhance our results and help transforming the Adaptive Execution Infrastructure from a functional prototype into a full-fledged solution for the environmental domain and beyond. Finally, we are interested in extending the hypercube-based architecture to support Cloud-based deployment of the Service Orchestration Engine. We anticipate that by moving the Adaptive Execution Infrastructure to the Cloud, we will be able to exploit elasticity capabilities for dynamically increasing or decreasing the hypercube dimension. This way, the execution engine will be able to more effectively and timely respond to workload changes.

Conclusion

Provide discussion of the overall coverage of the chapter and concluding remarks.

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  Data-driven adaptation. Running instances of the deployed BPEL processes are aware of information, which may come from external sources (i.e. third-party entities that were not anticipated at design-time). Moreover, they can leverage such data in order to alter their execution, and thereby enhance the performance of the execution infrastructure. Typical scenarios of data-driven adaptation include the cross-instance data re-use and sharing, the invocation of alternative services, the skipping of time-consuming activities, etc. Our Adaptive Execution Infrastructure is equipped with the mechanisms necessary to support adaptation by exploiting semantic and spatio-temporal annotations on the available data. Besides, the semantics-based data mediation engine provides for complex, ontology-based transformations.
  
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  Decentralized execution. A distributed architecture based on the hypercube P2P topology along with a set of algorithms that enable the decentralized execution of BPEL processes has been implemented. Our approach targets towards the improvement of the average process execution times and the enhancement of the overall throughput of the execution infrastructure in the presence of multiple long-running process instances that involve the exchange of large data. Such cases are typical in many applications, as well as in the environmental domain, where we validated our approach. The presented algorithms support the decomposition of a given BPEL process and the subsequent assignment of the constituent activities and data variables to the available hypercube nodes. Execution is then performed in a completely decentralized manner without the existence of a central coordinator.
  

References should relate only to the material you actually cited within your chapter (this is not a bibliography). References should be in APA style and listed in alphabetical order. Please do not include any abbreviations.

Author, A. A. (1994). Title of work. Location/City, State: Publisher.

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Wilfley, D. (1989). Interpersonal analyses of bulimia: Normal-weight and obese. Unpublished doctoral dissertation, University of Missouri, Columbia.

Lanktree, C., & Briere, J. (1991, January). Early data on the Trauma Symptom Checklist for Children (TSC-C). Paper presented at the meeting of the American Professional Society on the Abuse of Children, San Diego, CA.

Deci, E. L., & Ryan, R. M. (1991). A motivational approach to self: Integration in personality. In R. Dienstbier (Ed.), Nebraska Symposium on Motivation: Vol. 38. Perspectives on motivation (pp. 237-288). Lincoln: University of Nebraska Press.

VandenBos, G., Knapp, S., & Doe, J. (2001). Role of reference elements in the selection of resources by psychology undergraduates. Journal of Bibliographic Research, 5, 117-123. Retrieved October 13, 2001, from http://jbr.org/articles.html

In this section, please provide a list of 25-50 additional readings (e.g. journal articles, book chapters, case studies, etc.). You, as the contributing author(s), are the best source for suggestions on additional readings in your respective field. APA style must be followed for this section.

(Please refer to author checklist to see if this applies to your submission)

Keyword: Definition of Keyword.

Please provide 7-10 key terms related to the topic of your chapter and clear, concise definitions (in your own words) for each term. Place your terms and definitions after the references section of your chapter.