Ontologies are rapidly becoming popular in various research fields. There is a tendency both in converting existing models into ontologies and in creating new models. In this work we are focusing on Closed-Loop Product Lifecycle Management (PLM) models. An ontology model of a Product Data and Knowledge Management Semantic Object Model for PLM has been developed, with the aim of implementing ontology advantages and features into the model. An initial effort of developing the model into an ontology using Web Ontology Language-Description Logic (OWL-DL) is described in detail and the background and the motives for converting existing PLM models to ontologies is provided. The new model facilitates several of the OWL-DL capabilities, while maintaining previously achieved characteristics. Furthermore, a case study is presented based on application scenarios on the automotive industry. This case study deals with data integration and interoperability problems, in which a significant number of reasoning capabilities is implemented. (C) 2010 Elsevier B.V. All rights reserved.