It is possible to extract some data from Sony Ericsson DBK backups and save them as XML. Such dbk to xml conversion can be done with programs like phoneMiner or similar.
Another, completely different dbk to xml conversion be export of DocBook sources. These files share the same file extension and can be simply opened in any text editor, because they are already specially formated XMLs.Open DBK file Open XML file
A backup and recovery software for smartphones