To meet the requirements of interoperability, the enactment of workflow systems for processes should tackle the problem of data integration for effective data sharing and exchange. This paper aims at flexibly describing workflow entities and relationships by innovative ontology engineering, which are emerging in process-centred environments, supported by Resource Description Framework (RDF) based languages and tools. Our novel framework takes into consideration to position the ontology level in the data integration dimension. Having taken a more realistic approach towards interoperability, we present basic constructs of a workflow specific ontology, with a suite of classes and properties selectively created. In particular, we demonstrate an example description of Event Condition Action (ECA) rules by extensions of RDF. As an inter-lingua, the proposed vocabulary and semantics can be mapped onto other process description languages as well as the simple XML-based data representation of our earlier workflow prototype.