Memento Project

For Memento use on Wikipedia, see Wikipedia:Memento.

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.

The Memento logo

Technical description

Memento is defined in RFC 7089^[1] as an implementation of the time dimension of content negotiation, as defined by Tim Berners Lee in 1996.^[2] HTTP accomplishes negotiation of content via headers. The table below shows the different headers available for HTTP that allow clients and servers to find the 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.

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 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 2015-05-19 at the Wayback Machine
6. "Time Travel APIs". timetravel.mementoweb.org. from the original on 2018-05-21. Retrieved 2018-05-15.

External links

• Memento Project
• The When of the Web - Extensive information about the proposal and experiment is available in the November 2009 paper
• Memento: Time Travel for the Web
• http://lanlsource.lanl.gov/hello
• http://www.cdlib.org/cdlinfo/2010/02/04/web-archive-discovery-memento-implementation-meeting/