Figure 6: Relational function model of a pressure reducing valve.
Integrated hierarchical and relational function model
As already described in the introduction, by product reengineering a more structured solution space is required in order to enable innovative problem solving and not focus on a priori identified problem cores.
The integration of the two previously presented functional modelling approaches can provide a function model, which incorporates the benefits of the hierarchical and the relational function model as well. These are, the accurate modelling of the reality and the identification of entry points to the problem solving process through the formulation of problem statements as well as the hierarchically structured system’s image.
Figure 7 presents schematically the process steps for the introduced functional modelling approach. Thereby, a hierarchical function model is firstly set up, whereby the defined product’s main function is broken down to less abstract and more information containing functions. The functions are then classified to hierarchical levels according to the information they contain, as shown in chapter 4.1. The information has either to do with the constructive layout or with technological issues, which are considered to be more rudimental in the function hierarchy as defined in chapter 3 or with both of them.
The defined functions in the hierarchical model are afterwards used in order to set up a relational function model. Nevertheless, the hierarchical function model contains only useful functions, so the standard procedure of setting up a relational model is then applied in order to complement the function model with harmful functions. Furthermore, in this way function relations across a hierarchical level and different branches of the hierarchical model can recognized.
In the next step the defined hierarchical levels are integrated into the relational function model. Figure 8 shows a potential alternative for structuring the relational model. Thereby, the hierarchical levels are modelled as rings. The more central a function is located, the merrier abstract is the function. Furthermore, the quadrants of the middle ring stand for the branches of the hierarchical model.