1. A device for formulating numerical models of manufactured products by defining predetermined numerical data, comprising: a display unit; a storage unit configured to store numerical data for each model, the numerical data being representative of components constitutive of a manufactured product, variables and constraints; a processor configured to formulate a numerical model, the processor including a structure construction unit configured to generate and store in the storage unit numerical data corresponding to a structure of the manufactured product, the structure being a tree structure linking different structural components of the manufactured product, a constraint unit configured to define constraints for conformance with the numerical model, and a validation unit configured to display, on the display unit, the numerical data stored in the storage unit, and a plurality of validation selections to validate inclusion of the displayed numerical data of a previously formulated numerical model when executing the numerical model, wherein the display unit displays different specific acquisition windows of the user interface defining different formulation steps to formulate the numerical model, each specific acquisition window being configured to acquire all numerical data needed for one corresponding formulation step, each specific acquisition window and corresponding formulation step permitting a human operator of the device to define predetermined numerical data permitting constitution of the numerical model and to store the predetermined numerical data in memory, wherein said acquisition windows and corresponding formulation steps comprise: at least one structure construction acquisition window and structure construction formulation step, during which numerical data representative of a structure of a manufactured product defined by a tree structure linking the different structural components of said manufactured product are defined and stored in memory, at least one constraints acquisition window and constraints formulation step allowing constraints to be defined that are to be respected by every manufactured product in conformity with the numerical model, and at least one validation acquisition window and validation formulation step allowing validation of a previously formulated model, during which all of the data stored in memory are subject to validation selections to validate their employment in execution of the model, and wherein each acquisition window and said corresponding formulation step are further configured to execute a functional model that can be used to define a manufactured product configuration.