E-collaboration modeling standards like ISO/IEC 15944 and the UN/CEFACT Modeling Methodology (UMM) provide techniques, terms and reference models for modeling collaborative business processes. They offer a standardized approach for business partners to codify the business conventions, agreements and rules that govern business collaborations and to share business process information. Although effective in creating interoperability between organizations at the business process level, prospective business partners are required to commit to the same modeling standard. In this paper we show how the REA enterprise ontology can be used to semantically relate the ISO/IEC 15944 and UMM e-collaboration standards. Using the REA ontology as a shared business collaboration ontology, business partners can create interoperability between their respective business process models without having to use the same modeling standard.