I think the documentation at http://wiki.musicbrainz.org/XML_Webservice could be improved. Currently it groups together the options provided for different entities so:

It is very difficult to work out exactly what inc combinations are allowed for any top level entity,
It is not clear what the effect of and inc is (i.e inc=aliases, means aliases should be shown for what)
There is no example output either
This lack of clarity has contributed to some of the bugs introduced into the webservice since its launch

Would be clearer if we have a separate section for each toplevel entity as follows:

entityname (i.e release)

Explanation
inc values supported
Some example output

Also needs updating for Json output.