Ubuntu :: Changing "keypad Delete" From Comma To Period

I am using Ubuntu 9.10 in U.S. English with a German keyboard layout. Accordingly, pressing the delete button on the numeric keypad will produce a comma, which most applications do not recognize as a decimal. in order to have the key produce a period.

I have tried editing the /usr/share/X11/xkb/symbols/de and changing the line

Code:
include "kpdl(comma)"

in the "basic" section of the file to

Code:
include "kpdl(period)"

which seemed like the perfect solution, but upon restarting an error message pops up and the keyboard layout is changed to U.S. English.

Code:
cd /usr/share/X11/xkb/symbols
xkbcomp -lhlpR '*' -o ../symbols.dir

which does nothing at all if used with sudo and produces an error message if used without. Reverting changes to /usr/share/X11/xkb/symbols/de removes all errors.
Is there something else I need to do to have xkb accept my changes to the file?

Code:
include "kpdl(comma)"

does not specify a symbol to be mapped to the keypad delete key, but rather constitutes a command that integrates a pre-specified option into the layout file. Thus, simply removing the line works perfectly well, even without using the above suggestion to register the change to the file with xkb (or whatever it does).