How do I instantiate an FGEN instance for Atmels Figaro IDS in EDIF?

Specifically it's about how to specify the function to implement in the FGEN instance.

this I have as the cell definition early in the file:
[...]
        (cell fgen (cellType generic)
                (view fgen (viewType netlist)
                        (interface
                                (parameter FUNCTION (string ""))
                                (port A (direction INPUT))
                                (port B (direction INPUT))
                                (port C (direction INPUT))
                                (port D (direction INPUT))
                                (port G (direction OUTPUT))
                        )
                )
        )
[...]

later I have:
[...]
                                (instance C_fgen
                                        (viewRef fgen (cellRef fgen (libraryRef &_36_ATMEL_FPGA_47_cells)))
                                        (parameterAssign FUNCTION (string "A*B+C*D"))
                                )
[...]
cadences edif2fig program
chokes on the `string' token



Am I using `parameter' and `parameterAssign' correctly?
If not, what are their semantics?
Should I use `property' instead?

???