One of the key issues in connecting government systems is the fact that information must often be sent between security domains, but that information must not leak user-identifying or citizen-identifying information. XML helps greatly here, since it allows data to be redacted (selectively encrypted) as it passes between domains. XML-based security standards such as SAML also help. For example, a SAML Assertion can be used to assert that a user was authenticated in Domain A (e.g. a particular government agency) and then that SAML Assertion, with the user details encrypted or simply not present, can be sent over to Domain B. Also, SAML makes it possible to send just attribute information (such as a person's military rank, or their country of citizenship) within the assertions, and then that information can be used for access control at the recipient side.
