function — Defines a function by combining independent variables, breakpoints, and tables.
function :  name
     (description?, provenance?, 
          (
               (independentVarPts+, dependentVarPts)
 | 
               (independentVarRef+, dependentVarRef, functionDefn)
)
)
| name - the name of this function | 
Each function has optional description, optional provenance, and either a simple input/output values or references to more complete (possible multiple) input, output, and function data elements.
| DAVEfunc |