The specification must be one of three types: 
-# objective and constraint functions 
-# calibration (least squares) terms and constraint functions
-# a generic response functions specification.

These correspond to (a) optimization, (b) deterministic (least
squares) or stochastic (Bayesian) inversion, and (c) general-purpose
analyzer methods such as parameter studies, DACE, and UQ methods,
respectively.  Refer to \ref responses for additional details and
examples.
