I found a paper online that talks about watermarking .xmf files. It is a couple pages long but it looks very informative. Here is thre Abstract:
Abstract. Watermarking enables provable rights over content, which has been successfully applied in multimedia applications. However, it is not trivial to apply the known effective watermarking schemes to XML data, since noisy data may not be acceptable due to its structures and node extents. In this paper, we present two different watermarking schemes on XML data: the selective approach and the compression approach. The former allows us to embed non-destructive hidden information content over XML data. The latter takes verbosity and the need in updating XML data in real life into account. We conduct experiments on the efficiency and robustness of both approaches against different forms of attack, which shows that our proposed watermarking schemes are reasonably efficient and effective.
You can get your hands on the paper here:
https://smallpdf.com/shared#st=ee51a3ae ... nt&rf=link I highly suggest looking at Section 2 and Section 4 because I think they will be the most helpful for you.
Anyways, have a good day my dude. I hope this helped.