There are two distinct ".nff" formats:

The one represented by the objects in /pub/objects/nff and documented
in /pub/format_specs/nff.txt is the one used in Eric Haines' SPD
package.

The one represented by the objects in /pub/objects/nff-wtk and
documented in /pub/format_specs/nff-wtk.txt is the one used in
Sense8's WorldToolKit (WTK).

If you upload any .nff object, please specify what format/package it's
meant for.
