http://stackoverflow.com/questions/2837553/saml-vs-federated-login-with-oauth

SAML is a set of standards that have been defined to share information about who a user is, what his set of attributes are, and give you a way to grant/deny access to something or even request authentication.

OAuth is more about delegating access to something. You are basically allowing someone to "act" as you. Its most commonly used to grant access api's that can do something on your behalf.

They are two completely different things.

google 搜索 saml  vs oauth  会有很多