Description of problem:
Xerces-c27 (=xerces 2.7) is provided in the latest fedora (13) whereas xerces 2.8 is the latest in the xerces 2.X series.
According to the Xerces migration guide (http://xerces.apache.org/xerces-c/migrate-archive-3.html#API280), there is no API change between Xerces 2.7 and Xerces 2.8, so it could even be provided as an update.
Xerces 2.8 is required by some external applications including the belgium id card middleware (http://eid.belgium.be/fr/Comment_installer_l_eID/Linux/) which was supposed to work with fedora 12 as advertised on the page (never tested personaly).
The xerces-c27 package is here just to allow building perl-XML-Xerces which doesn't build with later versions. Feel free to package and submit for review a compatibility xerces-c28 package on the same model as xerces-c27 if you need.