1. A computer implemented method for integrating multiple engineering design systems in a computer aided design (CAD) system, comprising: (a) displaying, on a display device of the CAD system, a design generator configured, via an application programming interface (API), to accept input from a designer that results in the creation of an engineering design wherein the engineering design comprises two or more different worksheets, wherein each worksheet: (i) represents a different aspect of the engineering design; (ii) comprises one or more local design objects, wherein each local design object: (1) represents a functional aspect of a component; and (2) is independent from a physical representation of the component; (iii) comprises one or more relation objects, wherein each relation object models constraints of one or more properties of the one or more design objects; (b) organizing the one or more local design objects and one or more relation objects in an Functional Layout Document (FLD); (c) storing the FLD in a data center comprising a shared database within the CAD system, wherein the shared database is shared by the two or more worksheets; (d) using the FLD, via user input and the display device, to design the engineering design; and (e) creating one or more master design objects each comprised of an amalgamation of one or more of the local design objects from the two or more different worksheets, wherein: (i) each local design object in the master design object refers to a different particular aspect of the master design object; and (ii) each master design object manages all of its constituent local design objects.