4. The method of claim 1 , further comprising displaying a graphical rendering of one or more of said expression hierarchies concurrently within a view, the graphical rendering including text, shapes, and lines, the text including the contents of the formulas represented, by the nodes, the shapes representing the nodes, and the lines representing the edges connecting the nodes within said expression hierarchies.
6. The method of claim 4 , wherein said nodes are graphical rendered using separate physical properties including shape and color to denote different types or values of said operators or operands they represent.