Consider TeXML with Russian letters:
<TeXML>текст</TeXML>
Default translation to LaTeX produces:
\cyrchar\cyrt{}\cyrchar\cyre{}\cyrchar\cyrk{}....
The result is correct, but those who speak Russian prefer to see the real Russian letters instead of the substitutional commands.
To achieve this, specify the desired output encoding to the TeXML processor using the command line parameter --encoding (or -e). When the output encoding is, for example, koi8-r, the result is:
текст
Next step: “ASCII output”