Phase II: Product realization
This part of the methodology starts by identifying a list of available ingredients. For instance, cosmetic product designers are constrained to use approved ingredients, or they are limited to choose among the components in the company's inventory. Here, a binary variable is associated with each potential element, indicating whether it is selected or not as part of the formulation. Then, available heuristics regarding the choice and quantity of the ingredients are modeled as algebraic restrictions. As described in a previous publication,31 heuristics are usually first stated as logical conditions and then transformed into algebraic constraints, which involves binary variables. These heuristic-related restrictions, together with other known limits (e.g. technical and legal), help to reduce the design space, where the search could be then guided using the property models that relate product composition to the expected properties of the product.32