Content Comparison

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1. ID   – An identifier for the request. This must be unique.  Basically a random number. 
2. Version  – Indicate SAML version 
3. IssueInstant – Time instant of issue of the request. The time value is encoded in UTC
4. Apart from that,  One of following is a required attribute for LogoutRequest request…
5. BaseID or NameID or EncryptedID  
    This indicate the principle (user identifier).  Basically name that is known to both IDP and SP. 
   Also there are few optional elements
6. NotOnOrAfter  – The time at which the request expires in UTC
7. Reason  –  reason for the logout, in the form of a URI reference.
   1. There are two standard reasons 
      1. urn:oasis:names:tc:SAML:2.0:logout:user  – user terminates session and initiates logout
      2. urn:oasis:names:tc:SAML:2.0:logout:admin – admin terminates session and initiates logout
8. SessionIndex  – This is the session identifier that is used to identify the user session with both IDP and SP for given user.

Sources:

http://xacmlinfo.org/2013/06/28/how-saml2-single-logout-works/

https://azure.microsoft.com/en-us/documentation/articles/active-directory-single-sign-out-protocol-reference/