While a federation agreement is often discussed within the context of formal relationships, such as between an enterprise and an employee or between a government and a citizen, a federation agreement does not have to require any particular level of formality. For an IdP and a client, it is sufficient for a relationship to be established by something as simple as using a web form and confirmation email. For an IdP and an RP, it is sufficient for the IdP to publish contact information along with a public key and for the RP to use that data. Within the framework of ABFAB, it will generally be required that a mechanism exist for the IdP to be able to trust the identity of the RP; if this is not present, then the IdP cannot provide the assurances to the client that the identity of the RP has been established.