Thursday, November 19, 2009

2009-11-19: Memento Presentation and Movie; Press Coverage

On Monday, November 16 2009 Herbert and I went to the Library of Congress and presented slides from our Memento eprint (see the previous post for a short description of Memento). On Thursday, November 19 2009 Herbert gave the same presentation at OCLC.

Below are the slides that were presented as well as supporting movie. Fortunately, the slides & movie were finished in between ODU sporadically losing power over the weekend due to the Nor'easter, and on Tuesday when and were brought down by a disk failure. Thanks to Scott Ainsworth and the ODU systems staff for their yeoman's work on getting everything back up and running.

Slides & movie from the Library of Congress Brown Bag Seminar:

2010-02-12 Edit: The recorded presentation has just been uploaded to the Library of Congress web site.

Also, Memento has enjoyed considerable press & blog coverage. It began with an article in New Scientist:

Which was picked up and redistributed in various forms:'s-past

There was also coverage in the blog of The Chronicle of Higher Education:

As well as a few other blog posts:

And a mention on O'Reilly Radar:


Monday, November 9, 2009

2009-11-09: Eprint released for "Memento: Time Travel for the Web"

This is a follow-up to my post on October 5, where I mentioned the availability of the Memento project web site. Herbert's team and my team, working under an NDIIPP grant, have introduced a framework where you can browse the past web (i.e., old versions of web pages) in the same manner that you browse the current web. The framework uses HTTP content negotiation as a method for requesting the version of the page you want.

Most people know little about content negotiation, and the little they think they know is often wrong (see [1-3] for more information about CN). In a nutshell, CN allows you to link to a URI "foo" but, for example, without specifying its format (e.g., "foo.html" vs. "foo.pdf") or language ("foo.html.en" vs. ""). Your browser automatically passes preferences to the server (e.g., "I slightly prefer HTML over PDF, and I greatly prefer English to Spanish") and the server tries to find its best representation of "foo" that matches your preferences. In fact, CN defines 4 dimensions where the browser and server can negotiate the "best" representation: type, language, character set, and encoding (e.g., .gz vs. .zip).

We define a fifth dimension for CN: Datetime. If you configure your browser to prefer to view the web as it existed at a particular time, say January 29, 2008, then you could click on:

and not get the current version, but rather get an older version of the page (in this case, before Johnny Marr had joined the band).

There are two kinds of "tricks" that must be addressed to make this possible:

1. The client can be configured to specify the desired Datetime. Scott Ainsworth is currently developing a Firefox add-on for us and will be releasing "real soon now" (tm). In the mean time, you can play with a browser-based client developed by LANL just to see how it works.

2. The server must know how to "do the right thing" (tm). There are several ways to do this. One, if the server is running a content management system that keeps track of prior versions, then the server can respond with correct older version. For example, we have a plug-in for mediawiki that maps the incoming Datetime requests to the prior versions.

Or the production server can redirect the client to where it knows its pages are. For example, the following demo pages:

"know" about their corresponding transactional archives at and, respectively, and will redirect clients to the correct archive.

Third, the server can redirect the client to an aggregator we've developed (see the simple mod_rewrite rules that perform this function). For example, this rule is installed at; if the server there detects a Memento request, it will redirect the client to the aggregator which will search the Internet Archive, Archive-It, and other public web archives for the best Datetime match.

Finally, if the server is not configured to do any of those things, the Firefox add-on attempts to detect the server's non-compliance and redirect the client to the aggregator (for the same effect as described above).

The above is a short description of how Memento works. More details can be found in our eprint:

Herbert Van de Sompel, Michael L. Nelson, Robert Sanderson, Lyudmila L. Balakireva, Scott Ainsworth, Harihar Shankar, "Memento: Time Travel for the Web", arXiv 0911.1112, November 2009.

Also, we have a number of upcoming presentations where you can catch us explaining Memento in more detail:
We hope to see you at one of these meetings. Let us know if you have questions or comments.


1. Transparent Content Negotiation in HTTP, RFC 2295.
2. Content Negotiation, Apache HTTP Server Documentation.
3. ODU CS 595 Week 10 Lecture.

Sunday, November 8, 2009

2009-11-08: Back From Keynotes at WCI and RIBDA.

October was a busy travel month. On October 11-13, I attended a technical meeting for the Open Annotation Collaboration project at Berkeley, CA. From there, I traveled to Berlin, Germany to give a keynote about OAI-ORE at the Wireless Communication and Information Conference (WCI 2009). Michael Herzog was kind enough to invite me to speak there again; I also gave an invited talk at Media Production 2007, also in Berlin.

After a short week back in the US, it was off to Lima, Peru to give another keynote about OAI-ORE, this time at Reunión Interamericana de Bibliotecarios, Documentalistas y Especialistas en Información Agrícola, or RIBDA 2009. This was also another repeat performance -- I had given an invited talk about OAI-PMH in Lima in 2004, and my colleague there, Libio Huaroto, invited me back.

Slides from the keynotes are probably available on the conference web sites, however they were both edited versions of the more detailed ORE seminar I recently gave at Emory University in early October. Those interested in OAI-ORE should look at those slides or the "ORE in 10 minutes" video Herbert Van de Sompel recently uploaded to YouTube.