pythonOCC presentation at the 11th NASA-ESA Workshop on Product Data Exchange (http://step.nasa.gov/pde2009/). Abstract : The combination of open-source software and open standards are known to be considered as a key success factor of further technology development. The interest around the STEP standard is growing these last years, since the release of Application Protocols that allow to foresee new software solutions able to ensure a consistent product data description covering the whole lifecycle. This presentation focuses on the features of a free 3D modeling/data exchange library in the context of a research work dealing with the STEP AP239 standard for PDM/ERP interoperability. The goal is to merge these two approaches and describe the product from design to manufacturing, with a granularity that allow to keep the control over product configuration.