Global trends in the worldwide economy lead to new challenges for manufacturing enterprises and to new requirements regarding modeling industrial organizations, like integration of real-time information from operations and information about neighboring enterprises in the value network. Consequently, there is a need to design new, knowledge-based workflows and supporting software systems to increase efficiency of designing and maintaining new product ranges, production planning and manufacturing. The paper presents an approach to a specific aspect of enterprise modeling, product-process-machine modeling, derived from two real life case studies. It assumes ontology-based integration of various information sources and software systems and distinguishes four levels. The upper two levels (levels of product manager and product engineer) concentrate on customer requirements and product modeling. The lower two levels (levels of production engineer and production manager) focus on production process and production equipment modeling.