The Desktop Notifications framework provides a standard way of doing
passive pop-up notifications on the Linux desktop. These are designed
to notify the user of something without interrupting their work with a
dialog box that they must close. Passive popups can automatically
disappear after a short period of time.

This conflicts with xfce4-notifyd.  After removing the notification-daemon
package, you will need to reinstall xfce4-notifyd.

This requires GConf and libsexy.