Calc function names saved to file and backward compatibility

Hi,

I'm working on tdf#40835 again and experience a problem that is easily solved in the code, but does 
present backward compatibility problems in the saved (ods) documents.

There are 2 ODF functions (FDIST and LEGACY.FDIST) and 3 Excel functions (FDIST, F.DIST and 
F.DIST.RT).

In Calc, the current situation is:
Calc UI    ODF                      Excel
FDIST      LEGACY.FDIST             FDIST
F.DIST     COM.MICROSOFT.F.DIST     _xlfn.F.DIST
F.DIST.RT  COM.MICROSOFT.F.DIST.RT  _xlfn.F.DIST.RT
(ODF's FDIST is not used)

I think the desired situation is:
Calc UI    ODF                     Excel
FDIST      COM.MICROSOFT.FDIST     FDIST
F.DIST     FDIST                   _xlfn.F.DIST     
F.DIST.RT  LEGACY.FDIST            _xlfn.F.DIST.RT
(in case of UI's F.DIST, on export to Excel add argument cum=true, if absent)

These F-distribution functions are not unique having this problem, at least (ISO)WEEKNUM 
(tdf#50950) and probably other distribution functions share this.

I think an agreed method should be used to fix these problems, with the method to be determined (or 
is the method already defined?).
AKAICS, this method ranges from one code change (breaking compatibility with older versions and 
documents), via stepped code changes (maintaining compatibility for e.g. 2 Lo versions) to (but 
excluding) not changing anything.

I don't know if this is a developer/UX/ESC matter.

Looking forward to suggestions :-)


Winfried