Designing complex systems is an iterative process requiring constant updating of models representing related information. To ease consistent modelling, this paper focuses on linking function modelling with quantitative modelling. Therein, the IFM framework is used as vantage point which is to be coupled with the CPM/PDD approach. An extended class structure for the IFM framework is proposed incorporating the data model of CPM to enable the transition of information between them. This is illustrated with an example. Finally, implications and potentials for future research are discussed.