Metadata defines how configuration information shared between two communicating
entities is defined and shared. For instance, an entity's support for given SAML bindings, identifier information, and PKI information can be defined.
Metadata is defined by an XML Schema. The location of Metadata is defined using DNS records.
SAML 2.0 introduced a number of features not available in previous versions of the specification, including:
Pseudonyms – SAML 2.0 defines how an opaque pseudo-random identifier with no discenible correspondence with meaningful identifiers (for example, emails or account names) can be used between providers to represent principals. Pseudonyms are a key privacy-enabling technology because they inhibit collusion between multiple providers (as would be possible with a global identifier such as an email address).