The enterprise level software application that supports the strategic product-centric, lifecycle-oriented and information-driven Product Lifecycle Management business approach should enable engineers to develop and manage requirements within a Functional Digital Mock-Up. The integrated, model-based product design ENOVIA/CATIA V6 RFLP environment makes it possible to use parametric modelling among requirements, functions, logical units and physical organs. Simulation can therefore be used to verify that the design artefacts comply with the requirements. Nevertheless, when dealing with document-based specifications, the definition of the knowledge parameters for each requirement is a labour-intensive task. Indeed, analysts have no other alternative than to go through the voluminous specifications, to identify the performance requirements and design constraints, and to translate them into knowledge parameters. We propose to use natural language processing techniques to automatically generate Parametric Property-Based Requirements from unstructured and semi-structured specifications. We illustrate our approach through the design of a mechanical ring.