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Memento

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Datetime Negotiation Algorithm

The date algorithm Fedora uses to determine which LDPRm should be returned to a TimeGate request, as indicated by the value of the Acceptthe Accept-datetime Datetime header, is as follows: 

• Any AcceptAny Accept-datetime Datetime value that is earlier than the first/oldest Memento will return a reference to the first/oldest Memento. 
• Any AcceptAny Accept-datetime Datetime value that is later than a specific Memento’s timestamp but earlier than another Memento’s timestamp will return the older Memento. 
• An AcceptAn Accept-datetime Datetime value that matches a stored Memento datetime value perfectly will result in return the Memento preserved at that timestamp.
• An AcceptAn Accept-datetime Datetime value that is later than the last Memento will return a reference to the last/youngest Memento.

Fedora follows Memento Datetime negotiation pattern 1.1 as described in section 4.1.1 of the Memento specification, in which the Original Resource Acts as its own TimeGate (URI-R=URI-G; 302-Style Negotiation; Distinct URI-M).

Note bene

Fedora does not automatically initiate versioning for all resources.  The client MUST initiate versioning by invoking a special Link header at the time a resource is created.  See ?????

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