This work presents the product object model developed in the context of the EU-funded FP6-IST project named PROduct lifecycle Management and Information tracking using Smart Embedded systems (PROMISE), aiming at the closure of the whole set of information loops throughout the product lifecycle. The ultimate goals of the project are indeed to integrate product data from the entire lifecycle via different sources, to support comprehensive analysis on this data and to enhance by this the enterprise operational businesses. To achieve these goals, a set of hardware and software tools were developed. This paper presents the conceptual model behind one of the software components of this infrastructure, called the Product Data and Knowledge Management (PDKM) system, which is responsible for the integration and management of both product data and knowledge from all lifecycle phases, on a logically consistent basis. The same model also became the foundation for the proposal of a closed loop PLM standard.