Since 2013, I have been a principal contributor to the
Memento MediaWiki Extension. We recently released
version 2.2.0 to support MediaWiki versions of 1.31.1 and greater. During the extension's development, I have
detailed some of its concepts on this blog, I have
presented it at WikiConference USA 2014, and I have even
helped the W3C adopt it. It became the cornerstone of
my Master's Thesis, where I showed how the Memento MediaWiki Extension could help people
avoid spoilers on fan wikis. Why do Memento and MediaWiki belong together?
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| The "dimensions of genericity" table from "Web Architecture: Generic Resources" by Tim Berners-Lee in 1996, annotated to display the RFCs that implemented these dimensions for the Web. |
Memento is not limited to web archives. When Tim Berners-Lee was developing the Web,
he identified four dimensions of genericity: time, language, content-type, and target medium. HTTP enthusiasts will recognize that three of these became the
dimensions of content-negotiation that browsers handle for us invisibly. Time, however, was not handled until Memento. Memento provides a way to request not a specific language or file format, but the version of a page from a specific
time.
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Two timelines show the relationship between a live web page and a web archive capturing its mementos.
The top is the timeline of a live web page.
The bottom is the timeline of the observations of that page captured as mementos o1, o2, and o3.
We do not know what changes to the page the archive missed. |
As shown in the diagram above, web archives capture
observations of live web pages and store them as mementos. We have no knowledge of how often the page changed and which changes we missed. Web archives provide the only history of these pages.
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| Wikis hold every revision of a given page. |
Even though Memento was first deployed on web archives, it is applicable to any system that provides versioning. As shown in the screenshot above, wikis store all
revisions of a web page as mementos. We know how often a page changed because there is a record. When web archives capture wiki pages, they treat them like live web pages and often miss revisions, as shown in the diagram below. This makes wikis a more complete source of version information than web archives.
Wikis are web archives in their own right.
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Two timelines show a similar relationship between a wiki page and a web archive capturing its mementos.
The top is the timeline of revisions of that wiki.
The bottom line is a timeline of observations of that page captured as mementos o1, o2, and o3.
The web archive missed wiki revisions r3 and r4. |
Why do Memento and MediaWiki belong together? With a browser extension like
Memento for Chrome, or
Memento for Firefox, users can pick a date in the past and
seamlessly browse the Web as if it were that date. If Memento were supported by wikis, Memento would carry a user from a web archive observation to a wiki revision and back out to another site, all the while keeping them near their desired date. Who would need this functionality? In the next sections, I provide two scenarios where this would be useful. I then conclude with a section containing resources with more information about the Memento MediaWiki Extension.
Example Usage Scenarios
The Historian
Hanah is researching the Boston Marathon Bombing. The screenshots above show how the mementos for a single news article change as an event unfolds. To provide context to the earliest version of this article, Hannah wants to know what Wikipedia published about the event around 5 PM on April 19, 2013. Without Memento installed on Wikipedia, she would have to tediously scroll through pages of article history as shown in the animation below just to find the correct revision.
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| Anyone trying to find a specific revision in MediaWiki must scroll through pages of article history. |
Using the
Memento Extension for Chrome, she can set her browser to the date she needs. If Memento were installed on Wikipedia, she could visit her web archive pages and seamlessly transition to this wiki page at the same date, saving time. Even better, she could continue to browse Wikipedia and the rest of the Web with pages around the same date.
The Fan
I am a fan of many different fictional universes. Usually, because I am a PhD student, I cannot watch my favorite television shows on the night that they air. This does not mean that my fandom waits until I have caught up. The
Fandom (formerly Wikia) web site runs MediaWiki. As a
Star Trek fan, I watch
Star Trek: Discovery. The screenshot below contains a spoiler about one of the characters. The episode "Project Daedalus" aired on March 14, 2019. If had not seen the episode, I would immediately see a spoiler when visiting the current version of the page below.
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| The current version of this Fandom page contains a spoiler about this Star Trek character. |
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| The version of the page before the episode air date does not contain the spoiler. |
If I were using Memento, I could set the date in my browser and follow links to this page, as shown below.
However, I still see a spoiler? Why?
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| Even though I use Memento for Chrome and set my date prior to the date of the episode, I still get the spoiler? |
In
"Avoiding spoilers: wiki time travel with Sheldon Cooper," Michael Nelson, Herbert Van de Sompel, and I explain in more detail why this happens. Web archives only have access to some observations of a wiki page, and hence the nearest memento to the user's desired datetime is often correct. Because the wiki has access to all revisions, installing the Memento MediaWiki Extension directly on the wiki allows us to see the exact revision present at the desired datetime, thus avoiding this problem.
More Information About The Memento MediaWiki Extension
These are just two scenarios where users could benefit from wikis containing the Memento MediaWiki Extension. Can you think of others? Are there times when you wish you could have browsed the Wikipedia of the past? The following resources provide more information.
Memento provides access to any past resource on the Web. Wikis contain all previous versions of a page and thus are web archives in their own right. Do you know of a wiki that would benefit from Memento?
--
Shawn M. Jones
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