This paper presents an ontology-based software process assessment tool which was developed to support data collection phase of process assessment and to track conformance of software processes to CMMI as the process reference model. Ontology-based CMMI Mapping and Querying Tool (OCMQT) was developed as a plug-in to an open-source process management tool, namely EPF Composer which, is a realization of the process engineering meta-model SPEM. The study also explains findings from example usage of the OCMQT in a system and software development organization. In OCMQT, there is a need for expert knowledge. In fact, process improvement and assessment activities always require experts. However, OCMQT can protect non-expert personals from making unintended mistakes in an organization.