Every time a workflow solution is conceived there is a large amount of functionality that is eventually reinvented and redeveloped from scratch. Workflow management systems from academia to the commercial arena exhibit a myriad of approaches having as much in common as in contrast with each other. Efforts in standardizing a workflow reference model and the gradual endorsement of those standards have also not precluded developers from designing workflow systems tailored to specific user needs. This article is written in the belief that an appropriate set of common workflow functionality can be abstracted and reused in forthcoming systems or embedded in applications intended to become workflow-enabled. Specific requirements and a prototype implementation of such functionality, named Workflow Kernel, are discussed.