Which format is the most commonly used standard for exchanging information within a federated identity...

Security Assertion Markup Language (SAML) is the most common data format for information exchange within a federated identity system. It is used to transmit and exchange authentication and authorization data.XML is similar to SAML, but it's used for general-purpose data encoding and labeling and is not used for the exchange of authentication and authorization data in the way that SAML is for federated systems. JSON is used similarly to XML, as a text-based data exchange format that typically uses attribute-value pairings, but it's not used for authentication and authorization exchange. HTML is used only for encoding web pages for web browsers and is not used for data exchange--and certainly not in a federated system.