Community-Contributed Media Collections: Knowledge at Our Fingertips - Community-Built Databases: Research and Development - page 25

see the group but only “invited” users can join it, and (c) private, where the group is
hidden from the community and an invitation is required both to see and to join it.
Browsing techniques and diverse sophisticated search functionalities are also
available on Flickr. For example, it is possible to filter the search results according
to geographical locations, time intervals and media type.
Since community-built photo collections are typically very conspicuous in size,
the efficient browsing of these collections is still an open research issue. Different
approaches aimed at improving the browsing of large image collections have been
proposed in the literature [ 9 , 10 ].
2.2.3 Wikipedia
Wikipedia [ 3 ] is a free, collaborative, multilingual encyclopedia. Any Web user
can collaborate to create or edit a Wikipedia page. Since 2001, this effort of the
Web community has produced over 15 million articles. The corpus is composed
of several collections of articles in different languages. For example, the English
version contains over 3.2 million articles at March 2010, whereas the German
version contains more than 1 million.
In recent years, Wikipedia has been considered the most powerful, accurate, and
complete available free encyclopedia. Due to its nature, Wikipedia is one of the
most dynamic and fastest-growing resources over the Web. For instance, articles
about events are often added within few days from their occurrence. Moreover,
since everyone can edit the information, errors are usually removed after few
revisions by other Web users. Unlike other encyclopedias, Wikipedia is freely
available and covers a huge number of topics. For example, Encyclopedia Brit-
annica, one of the oldest encyclopedias which is considered a reference topic for the
English language, with articles typically contributed by experts, contains only
around 120,000 articles in the last release. Indeed in [ 11 ] Wikipedia was found to
be very similar, in terms of accuracy, to Encyclopedia Britannica, but the coverage
of topics is greater.
The main advantage of Wikipedia is its community, which improves and con-
trols the content of the encyclopedia. Except for a few pages, every article may be
edited anonymously or with a user account, while only registered users may create a
new article. Once a new article has been added, the page is owned by the commu-
nity, which can modify the content. Even though every Web user can contribute to
the growth of the encyclopedia, the Wikipedia community has established “a
bureaucracy of sorts”, including a clear power structure that gives volunteer
administrators the authority to exercise editorial control. The administrators are a
group of privileged users who have the ability to delete pages, lock articles from
being changed in case of vandalism or editorial disputes, and block users from
editing.
Since many Web users may not be proficient at creating and managing Web
content, the editing model of Wikipedia is based on “wiki”. This technology allows