19. The non-transitory computer-readable storage medium of claim 11 , wherein the constraint file comprises a parameterizable constraint evaluated at runtime, wherein the parameterizable constraint for a selected instance of a parameterizable module depends upon a parameter value from the selected instance of the parameterizable module.
19. The non-transitory computer-readable storage medium of claim 11 , wherein the constraint file comprises a parameterizable constraint evaluated at runtime, wherein the parameterizable constraint for a selected instance of a parameterizable module depends upon a parameter value from the selected instance of the parameterizable module. 20. The non-transitory computer-readable storage medium of claim 19 , wherein the parameterizable constraint is specified using a scripting language.