How do you indicate non-translatable parts of a translatable string? I’m interested in your best practises and advice.

Let’s assume the file format concerned is XML, and XLIFF at that. And let’s also assume these source strings are in English and must be optimized for as much translation automation as possible (MT, TM, other string leveraging techniques, and so on).

I would have thought the obvious solution was to do something like use the mrk element in the source segment. For example:

<source>Please translator, do not translate the word <mrk mtype=”protected”>Groovy</mrk>. The word <mrk mtype=”protected”>Groovy</mrk> refers to an agile dynamic language for the <mrk mtype=”protected”>Java</mrk> platform and should remain in English.</source>

How would you do it given the assumptions above?