Current auditing procedures struggle with the incorporation of new data-driven techniques such as Process Mining. Although Process Mining has been applied experimentally on micro-level workflow processes, it is not so easy to apply on the level of the value cycle that is at the core of accounting databases. A more general problem is that the new smart approaches lack a well-developed accounting ontology. The REA business ontology does offer such an ontology but so far, its main focus has been on accounting database design. In this paper, a Petri Net specification of REA is proposed for ontology-based process analysis. This specification makes it possible to express more than the traditional static specification. The paper also describes how REA Petri Nets can be developed using Process Mining and how they can be applied in a Continuous Auditing framework.