How to mark Docbook sentences as not translatable

[Pierre Wieser <pwieser trychlos org>]

Hi all,

Well, all is in the subject :)

The user's manual of NACT application is written with Docbook.
Translators make their best efforts to translate the manual
efficiently, but the need has arisen to mark some phrases as 
"not translatable".

How should I do this ?

Some Google search only directed me to ITS [1], but I am not
sure if this extension is managed by Gnome translation toolchain ?

Thanks in advance.
Regards
Pierre

[1] http://www.w3.org/TR/xml-i18n-bp/#docbook