A continuous workflow scheduling framework

Traditional workflow management or enactment systems (WfMS) and workflow design processes view the workflow as a one-time interaction with the various data sources, i.e., when a workflow is invoked, its steps are executed once and in-order. The fundamental underlying assumption has been that data sources are passive and all interactions are structured along the request/reply (query) model. Hence, traditional WfMS cannot effectively support business or scientific monitoring applications that require the processing of data streams such as those generated nowadays by sensing devices as well as mobile and web applications. Our hypothesis is that WfMS, both in the scientific and business domains, can be extended to support data stream semantics to enable monitoring applications. This includes the ability to apply flexible bounds on unbounded data streams and the ability to facilitate on-the-fly processing of bounded bundles of data (window semantics). In our previous work we have developed and implemented a Continuous Workflow Model that supports our hypothesis. This implementation of a CONtinuous workFLow ExeCution Engine (CONFLuEnCE) led to the realization that different applications have different performance requirements and hence an integrated workflow scheduling framework is essential. Such a framework is the main contribution of this paper. In particular, we designed and implemented STAFiLOS, a STreAm FLOw Scheduling for Continuous Workflows framework within CONFLuEnCE and evaluated STAFiLOS based on the Linear Road Benchmark.