Data collection by the user is empirical : the parameters are chosen freely, their relevance is analysed by a correlation study. Projects in the same database must belong to the same technological family. Costs have to be standardized via parameters in order to avoid distortion due to inflation, currency differences, etc. Technical parameters can be numerical quantities (like a weight, a volume, a number of parts…) or represent an ordinal classification (quality class, type of operation…).

Step 2 : Generation of the parametric model