The first paragraph of a documentation comment is used as the short description of the class (or whatever the documentation comment applies to) - currently it's too long really - compare with the other classes (the short descriptions are the right hand table cell):

http://xapian.org/docs/apidoc/html/annotated.html

I'd suggest ending the first paragraph where the comma currently is.

We also conventionally put two spaces after the '*' on subsequent lines of a documentation comment so the left margin lines up with the first line.