This document discusses several websites that utilize user-contributed metadata or tagging. These include Flickr for photo sharing, Delicious for bookmark sharing, Wikipedia for collaborative editing of encyclopedia entries, Technorati for blog tagging, and LibraryThing for tagging personal book collections. It also mentions PennTags for tagging university resources, Steve for tagging museum items, Connotea and CiteULike for tagging academic papers, and ESP Game and Google Image Labeler for collaborative image tagging. Amazon Mechanical Turk is also discussed as a service for crowdsourcing tasks.

1. Some sites using user-contributed metadata
Flickr <http://www.flickr.com/> is an online photo sharing site, which states “help
people make their photos available to the people who matter to them” and “enable new
ways of organizing photos” as its two main goals.
Del.icio.us <http://del.icio.us/> is a site for tagging and sharing Web sites, including “our
favorite articles, blogs, music, restaurant reviews, and more.”
Wikipedia <http://www.wikipedia.org> is an online, entirely user-created encyclopedia.
Any registered user can create or edit entries. Some level of editorial control exists, but in
general the community relies on its users to monitor the quality of content.
Technorati <http://www.technorati.com/> is a popular site for exploring creator-tagged
blog entries (among a few other things).
LibraryThing <http://www.librarything.com/> is an application of tagging to personal
book collections. It can pull bibliographic information from the Library of Congress or
amazon.com, saving users the time of entering this information manually. A free account
allows a user to tag and manage up to 200 books. The site also features disambiguation
mechanisms whereby users can tell the system that two books represent the same work,
or two authors represent the same person. Perhaps LibraryThing’s most important and
innovative feature is providing recommendations for new books to read based on the tags
a user has applied to his collection.
PennTags <http://tags.library.upenn.edu/> is a tagging site intended for the University of
Pennsylvania community. In addition to tagging Web sites, PennTags allows users to tag
records from the Penn online catalog and individual journal articles. It represents an
interesting move by a library into the tagging community.
Steve <http://www.steve.museum/> is an initiative from the museum community to
harness the efforts of knowledgeable users in describing museum resources. Steve is
unusual for a tagging initiative in that users don’t select their own resources to tag, but
rather are presented with system-selected resources for tagging. It remains to be seen if
the data produced by tagging in this type of environment results in the rich data provided
by users describing their own resources.
Connotea <http://www.connotea.org/> is a tagging site intended for “researchers and
clinicians” to “keep links to the articles you read and the websites you use, and a place to
find them again.” It markets itself as a way for scientists to organize scholarly reference
lists, and originated from the Nature Publishing Group.
CiteULike <http://www.citeulike.org/> “is a free service to help academics to share,
store, and organise the academic papers they are reading.” Users tag citations, and add
them to personal libraries.

2. 2
ESP Game <http://www.espgame.org/> from Carnegie Mellon University collects labels
for images on the Web from users by pairing two users online at the same time and
challenging them to agree on a label for a series of images. They offer an image search
<http://www.captcha.net/esp-search.html> using the labels they’ve collected through the
game.
Google Image Labeler <http://images.google.com/imagelabeler/> also matches users
with partners to label images. When two users agree on a label, a new image is displayed
for labeling. Points are awarded based on how many images were labeled before time
runs out.
Amazon Mechanical Turk <http://www.mturk.com/mturk/welcome> is a service that
matches tasks easily performed by humans with software applications that need the
information provided by those tasks. Individuals who complete tasks earn small amounts
of money, generally less than a dollar. The service includes an API so that developers can
integrate the service into their applications.

3. 3
Further reading
Bearman, David and Jennifer Trant. “Social Terminology Enhancement through
Vernacular Engagement,” D-Lib Magazine, 11(9), 2005.
http://www.dlib.org/dlib/september05/bearman/09bearman.html
Golder, Scott A. & Bernardo A. Huberman, “The Structure of Collaborative Tagging
Systems,” Journal of Information Science 32 (2), 2006, 198–208.
Hammond, Tony, Timo Hannay, Ben Lund, and Joanna Scott, “Social Bookmarking
Tools (I): A General Review,” D-Lib Magazine, 11(4), 2005.
http://www.dlib.org/dlib/april05/hammond/04hammond.html
Kroski, Ellyssa, “The Hive Mind: Folksonomies and User-Based Tagging,”
http://infotangle.blogsome.com/2005/12/07/the-hive-mind-folksonomies-and-user-based-
tagging/
Lund, Ben, Tony Hammond, Martin Flack, and Timo Hannay, “Social Bookmarking
Tools (II): A Case Study – Connotea,” D-Lib Magazine, 11(4), 2005.
http://www.dlib.org/dlib/april05/lund/04lund.html
Mathes, Adam, “Folksonomies – Cooperative Classification and Communication
Through Shared Metadata.” Computer Mediated Communication – LIS590CMC,
Graduate School of Library and Information Science, University of Illinois Urbana-
Champaign, December 2004. http://www.adammathes.com/academic/computer-
mediated-communication/folksonomies.html.
Peterson-Lugo, Billie. “Tech Talk: Folksonomy,” Library Instruction Round Table News,
29(1), September 2006. http://www3.baylor.edu/LIRT/lirtnews/2006/sept06.pdf
Shirkey, Clay. “Ontology is Overrated: Categories, Links, and Tags”
http://www.shirky.com/writings/ontology_overrated.html
van Hooland, Seth. “From Spectator to Annotator: Possibilities offered by User-
Generated Metadata for Digital Cultural Heritage Collections,” September 2006
http://homepages.ulb.ac.be/~svhoolan/usergeneratedmetadata.pdf
You’re It! A Blog on Tagging http://tagsonomy.com/