Self-coordination of Workflow Execution Through Molecular Composition

With the development of the Internet of Services, composing loosely-coupled, distributed and autonomous services dynamically has become one of the new challenges for large scale computing. While service composition systems are now a key feature of service oriented architectures, they are usually managed by a central coordination node, leading to performance and communication bottlenecks at runtime, as well as reliability issues. Accordingly, workflow executable languages, such as BPEL was designed to support centralized and static coordination of workflows. Thus, it appears crucial to promote service composition systems with a proper support for decentralized and dynamic coordination. Recently, nature metaphors have been shown of interest for inspiring autonomous coordination in service architectures. In this paper, we present a new analogy for service coordination based on molecular composition. Within this analogy, data and services are molecules floating and interacting freely in a chemical solution. The decentralized workflow execution coordination is achieved through a set of reactions between those molecules. In more concrete terms, we express this coordination with HOCL, a chemical higher-order language, in which reaction rules are themselves molecules able to react. These rules are composed, allowing a wide variety of workflow patterns to be executed. We here extend the notion of chemical computing, by proposing an executable chemical language for decentralized workflow execution.