The Memento logo

Memento is a United States National Digital Information Infrastructure and Preservation Program (NDIIPP)–funded project aimed at making Web-archived content more readily discoverable and accessible to the public.

Technical description

Memento is defined in RFC 7089[1] as an implementation of the time dimension of content negotiation.[2] HTTP accomplishes negotiation of content via a variety of headers that allow clients and servers to find content that the user desires.

Dimensions of Content Negotiation Provided by HTTP
Request Header Response Header Dimension Examples Reference
Accept Content-Type content-type of the representation text/html

text/plain image/png

 RFC 7231[3]

RFC 2616

Accept-Language Content-Language language of the representation en

en-US cz

 RFC 7231

RFC 2616

Accept-Encoding Content-Encoding medium, typically compression, that the content has been encoded with compress

gzip deflate

 RFC 7231

RFC 2616

Accept-Charset Content -Type the character set used by the web page iso-8859-5

unicode-1-1

 RFC. 
7231

RFC 2616

Accept-Datetime Memento-Datetime time of the representation Fri, 15 Aug 2014 13:43:03

GMT

 RFC 7089


To understand Memento fully, one must realize that the Last-Modified header provided by HTTP[4] does not necessarily reflect when a particular version of a web page came into existence. Also, the Last-Modified header may not exist in some cases. To provide more information, the Memento-Datetime header has been introduced to indicate when a specific representation of a web page was observed on the web.[5]

This diagram shows how Memento uses a TimeGate (URI-G) to find the best archived page (URI-M) for a user, given the original resource (URI-R) and a datetime.
This diagram shows how Memento uses a TimeGate (URI-G) to find the best archived page (URI-M) for a user, given the original resource (URI-R) and a datetime.

Usage

One can find copies of page by simply navigating, in a web browser, to a link formatted, replacing urltoarchive with the full URL of the page desired:[6]

JSON description of a Memento:

http://timetravel.mementoweb.org/api/json/YYYY/urltoarchive
http://timetravel.mementoweb.org/api/json/YYYYMM/urltoarchive
http://timetravel.mementoweb.org/api/json/YYYYMMDD/urltoarchive
http://timetravel.mementoweb.org/api/json/YYYYMMDDHH/urltoarchive
http://timetravel.mementoweb.org/api/json/YYYYMMDDHHMM/urltoarchive
or

redirect to a Memento with a datetime that is close to a desired datetime:

http://timetravel.mementoweb.org/memento/YYYY/urltoarchive
http://timetravel.mementoweb.org/memento/YYYYMM/urltoarchive
http://timetravel.mementoweb.org/memento/YYYYMMDD/urltoarchive
http://timetravel.mementoweb.org/memento/YYYYMMDDHH/urltoarchive
http://timetravel.mementoweb.org/memento/YYYYMMDDHHMM/urltoarchive

References

  1. ↑ RFC 7089: HTTP Framework for Time-Based Access to Resource States -- Memento
  2. ↑ Berners Lee, Tim. "Web Architecture: Generic Resources". World Wide Web Consortium (W3C). 1996. http://www.w3.org/DesignIssues/Generic Archived 2015-06-02 at the Wayback Machine
  3. ↑ RFC 7231: Hypertext Transfer Protocol (HTTP/1.1): Semantics and Content
  4. ↑ RFC 7232: Hypertext Transfer Protocol (HTTP/1.1): Conditional Requests
  5. ↑ Nelson, Michael L. "2010-11-05: Memento-Datetime is not Last-Modified". Web Science and Digital Libraries Research Group. November 5, 2010. http://ws-dl.blogspot.com/2010/11/2010-11-05-memento-datetime-is-not-last.html Archived 2015-05-19 at the Wayback Machine
  6. ↑ "Time Travel APIs". timetravel.mementoweb.org. Archived from the original on 2018-05-21. Retrieved 2018-05-15.
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