4. A method as in claim 1 , further comprising: inserting a recycle function in the functional model to return one of a material, an energy flow or a signal to a predecessor function.
4. A method as in claim 1 , further comprising: inserting a recycle function in the functional model to return one of a material, an energy flow or a signal to a predecessor function. 7. A method as in claim 4 , wherein a location for inserting the recycle function in the functional model is manually selected.