DACS can be configured to federate two or more web servers. Once federated, each web server recognizes users that have authenticated themselves at any of the servers in the federation; this capability is known as single sign-on. Each web server remains autonomous with respect to controlling access to its resources. Access control rules can be written for any of the servers to grant, deny, or restrict a particular user's access to its resources.
A DACS federation can interoperate with other DACS federations and other identity management systems by exporting (or importing) identities.
If you are interested in federated identity management, DACS can do the hard parts for you - all that is usually required of a web administrator is configuration and "look & feel" integration with the existing web site. And if authentication using RFC 2617 Basic or Digest Authentication is all you require, or if you need to authenticate against an existing Apache password file, then you can get going quickly.