In plant engineering, every product is unique and customer-specific. This means that the entire development process must be run through for each plant, although there is a high proportion of repeat components. Established methods of identifying them in product data management (PDM) are based on the evaluation of building structures and fail in plant engineering, since it is precisely the building structure that is unique and never repeats itself. In contrast, functional structures are much more customer-independent and still provide a complete and detailed product description. This article presents a core model proposal for using function structuring for part repetition in PDM.