At this link XING tells us, that they accept XML files in a certain format for uploading events to their site. They supply us with some nice but rather informal documentation in PDF, but there is no schema. Now that made me a little curious today, I downloaded their template file, created a few variants of the sample entry, and running trang I created a RELAX-NG schema file (anybody interested?). trang seems to not recognise date-time values of tags, so that always needs a little manual post-processing.
O, yes, I proudly uploaded one such event that way. (Actually on the first attempt I got the year wrong, that was quite embarrassing.)