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Open Directory Project

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Open Directory Project
URL http://dmoz.org/
Commercial? No
Type of site Web directory
Registration Optional
Owner Netscape
Created by Netscape
Launched June 5, 1998

The Open Directory Project (ODP), also known as dmoz (from directory.mozilla.org, its original domain name), is a multilingual open content directory of World Wide Web links owned by Netscape that is constructed and maintained by a community of volunteer editors.

ODP uses a hierarchical ontology scheme for organizing site listings. Listings on a similar topic are grouped into categories, which can then include smaller categories.



Project information

ODP was founded as Gnuhoo by Rich Skrenta and Bob Truel in 1998. At the time, Skrenta and Truel were working as engineers for Sun Microsystems. Chris Tolles, who worked at Sun Microsystems as the head of marketing for network security products, also signed on in 1998 as a co-founder of Gnuhoo along with co-founders Bryn Dole and Jeremy Wenokur. Skrenta was already well known for his role in developing TASS, an ancestor of tin, the popular threaded Usenet newsreader for Unix systems. Coincidentally, the original category structure of the Gnuhoo directory was based loosely on the structure of Usenet newsgroups then in existence.

The Gnuhoo directory went live on June 5, 1998. After a Slashdot article suggested that Gnuhoo had nothing in common with the spirit of free software,[1] for which the GNU project was known, Richard Stallman and the Free Software Foundation objected to the usage of Gnu. So Gnuhoo was changed to NewHoo. Yahoo then objected to the usage of "Hoo" in the name, prompting them to switch the name again. ZURL was the likely choice. However, before the switch to ZURL, NewHoo was acquired by Netscape Communications Corporation in October of 1998 and became the Open Directory Project. Netscape released the ODP data under the Open Directory License. Netscape was acquired by AOL shortly thereafter, and ODP was one of the assets included in the acquisition. AOL later merged with Time-Warner.

By the time Netscape assumed stewardship, the Open Directory Project had about 100,000 URLs indexed with contributions from about 4500 editors. On October 5, 1999, the number of URLs indexed by ODP reached one million. According to an unofficial estimate, the number of URLs in the Open Directory surpassed the number of URLs in the Yahoo! Directory in April 2000 with about 1.6 million URLs. ODP achieved the milestones of indexing two million URLs on August 14, 2000, three million listings on November 18, 2001 and four million on December 3, 2003.

From January 2006 the Open Directory began to publish online reports to inform the public about the development of the project. The first report covered the year 2005. Monthly reports have been issued subsequently.

These reports give greater insight into the functioning of the directory than the simplified statistics given on the front page of the directory. The number of listings and categories cited on the front page include "Test" and "Bookmarks" categories, but these are not included in the RDF dump offered to users. The total number of editors who have contributed to the directory as of March 31 2007 was 75,151.[2] The number of active editors at any instant is much lower, for example there were 7407 active editors during August 2006.[3]

System failure and editing outage, October to December 2006

On October 20, 2006, the ODP's main server suffered a catastrophic system failure[4] that prevented editors from working on the directory until December 18, 2006.[5] During that period, an older build of the directory was visible to the public. On January 13, 2007, the Site Suggestion and Update Listings forms were again made available.[6] On January 26, 2007, weekly publication of RDF dumps resumed. To avoid future outages, the system now resides on a redundant configuration of two Intel-based servers.[7]

Competing and spinoff projects

ODP inspired the formation of two other major web directories edited by volunteers and sponsored by public companies, both now defunct: Go.com directory (formerly owned by The Walt Disney Company), and Zeal (formerly owned by LookSmart). These directories did not license their content for open content distribution, which may have contributed to their demise; open content licensing contributed to ODP's success in a fiercely competitive market.

The concept of using a large-scale community of editors to compile online content has been successfully applied to other types of projects. ODP's editing model directly inspired three other open content volunteer projects: an open content restaurant directory known as ChefMoz (launched by ODP management), an open content music directory known as MusicMoz, and an encyclopedia known as Open Site. As yet, none of these has approached ODP's level of success.


Open Directory Project front page, January 2006
Open Directory Project front page, January 2006

Gnuhoo borrowed its initial ontology from Usenet. For example, the topic covered by the comp.ai.alife newsgroup was represented by the category Computers/AI/Artificial_Life. The original divisions were for Adult, Arts, Business, Computers, Games, Health, Home, News, Recreation, Reference, Regional, Science, Shopping, Society, and Sports. While these fifteen top-level categories have remained intact, the ontology of second- and lower-level categories has undergone a gradual evolution; significant changes are initiated by discussion among editors, and then implemented when consensus has been reached.

In July 1998, the directory became multilingual with the addition of the World top-level category. The remainder of the directory lists only English language sites. By May 2005, seventy-five languages were represented. The growth rate of the non-English components of the directory has been greater than the English component since 2002. While the English component of the directory held almost 75% of the sites in 2003, the World level grew to over 1.5 million sites as of May 2005, forming roughly one third of the directory. Ontology in non-English categories generally mirrors that of the English directory, although exceptions which reflect language differences are quite common.

Several of the top-level categories have unique characteristics. The Adult category is not present on the directory homepage, but it is fully available in the RDF dump that ODP provides. While the bulk of the directory is categorized primarily by topic, the Regional category is categorized primarily by region. This has led many to view ODP as two parallel directories: Regional and Topical.

On November 14, 2000, a special directory within the Open Directory was created for people under 18 years of age.[8] Key factors distinguishing this "Kids and Teens" area [1] from the main directory are:

  • Stricter guidelines which limit the listing of sites to those which are targeted or appropriate for people under 18 years of age.[2]
  • Category names as well as site descriptions use vocabulary which is age appropriate.
  • Age tags on each listing distinguish content appropriate for kids (age 12 and under), teens (13 to 15 years old) and mature teens (16 to 18 years old).
  • Kids and Teens content is available as a separate RDF dump.
  • Editing permissions are such that the community is parallel to that of the Open Directory.

By May 2005, this portion of the Open Directory included over 32,000 site listings.

Since early 2004 the whole site has been in UTF-8 encoding. Prior to this, the encoding used to be ISO 8859-1 for English language categories, and a language-dependent character set for other languages. The RDF dumps have been encoded in UTF-8 since early 2000.


Directory listings are maintained by editors. While some editors focus on the addition of new listings, others focus on maintaining the existing listings. This includes tasks such as the editing of individual listings to correcting spelling and/or grammatical errors, as well as monitoring the status of linked sites. Still others go through site submissions to remove spam and duplicate submissions.

Robozilla is a web crawler written to check the status of all sites listed in ODP. Periodically, Robozilla will flag sites which appear to have moved or disappeared, and editors follow up to check the sites and take action. This process is critical for the directory in striving to achieve one of its founding goals: to reduce the link rot in web directories. Shortly after each run the sites marked with errors are automatically moved to the unreviewed queue where editors may investigate them when time permits.

Due to the popularity of the Open Directory and its resulting impact on search engine rankings (See PageRank), domains with lapsed registration that are listed on ODP have attracted domain hijacking, an issue that has been addressed by regularly removing expired domains from the directory.

While corporate funding and staff for the ODP have diminished in recent years, volunteerism has resulted in the creation of new and improved editing tools, such as linkcheckers to supplement Robozilla, category crawlers, spellcheckers, search tools that directly sift a recent RDF dump, bookmarklets to help automate some editing functions, and tools to help work through unreviewed queues in multiple ways.

License and requirements

ODP data is made available for open content distribution under the terms of the Open Directory License, which requires a specific ODP attribution table on every Web page that uses the data.

The Open Directory License also includes a requirement that users of the data continually check the ODP site for updates and discontinue use and distribution of the data or works derived from the data once an update occurs. This restriction prompted the Free Software Foundation to refer to the Open Directory License as a non free documentation license, citing the right to redistribute a given version not being permanent, and the requirement to check for changes to the license.

RDF dumps

ODP data is made available through an RDF-like dump that is published on a dedicated download server [3]. An archive of previous versions is also available [4]. New versions are usually generated weekly. An ODP editor has catalogued a number of bugs that are/were encountered when implementing the ODP RDF dump, including UTF-8 encoding errors (fixed since August 2004) and an RDF format that does not comply with the final RDF specification because ODP RDF generation was implemented before the RDF specification was finalized [5].

So while today the so-called RDF dump is valid XML, it is not strictly RDF, but an ODP-specific format. Software to process the ODP RDF dump needs to take account of this.

Content users

ODP data powers the core directory services for many of the Web's largest search engines and portals, including Netscape Search, AOL Search, Google, and Alexa.

Other uses are also made of ODP data. For example, in the spring of 2004 Overture announced a search service for third parties combining Yahoo! Directory search results with ODP titles, descriptions and category metadata. The search engine Gigablast announced on 12 May 2005 its searchable copy of the Open Directory. The technology permits search of websites listed in specific categories, "in effect, instantly creating over 500,000 vertical search engines".[6]

As of September 8, 2006 the ODP listed 313 English-language Web sites that use ODP data as well as 238 sites in other languages.[7] However these figures do not reflect the full picture of use, as those sites which use ODP data without following the terms of the ODP license are not listed.

Policies and procedures

There are restrictions imposed on who can become an ODP editor. The primary gatekeeping mechanism is an editor application process wherein editor candidates demonstrate their editing abilities, disclose affiliations that might pose a conflict of interest, and otherwise give a sense of how the applicant would likely mesh with the ODP culture and mission. A majority of applications are rejected, but reapplying is allowed and sometimes encouraged. The same standards apply to editors of all categories and subcategories, which can result in certain areas going without editors for long periods of time.[citation needed]

ODP's editing model is a hierarchical one. Upon becoming editors, individuals will generally have editing permissions in only a small category. Once they have demonstrated basic editing skills in compliance with the Editing Guidelines, they are welcome to apply for additional editing privileges, in either a broader category, or in a category elsewhere in the directory. Mentorship relationships between editors are encouraged, and internal forums provide a vehicle for new editors to ask questions.

ODP has its own internal forums, the contents of which are intended only for editors to communicate with each other[9] primarily about editing topics. Access to the forums requires an editor account, and editors are expected to keep the contents of these forums private.[10]

Over time, senior editors may be granted additional privileges which reflect their editing experience and leadership within the editing community. The most straightforward are editall privileges, which allow an editor to access all categories in the directory. Meta privileges additionally allow editors to perform tasks such as reviewing editor applications, setting category features, and handling external and internal abuse reports. Cateditall privileges are similar to editall, but only for a single directory category. Similarly, catmod privileges are similar to meta, but only for a single directory category. Catmv privileges allow editors to make changes to directory ontology by moving or renaming categories. All of these privileges are granted by admins and staff, usually after discussion with meta editors.

In August 2004, a new level of privileges called admin was introduced. Administrator status was granted to a number of long serving metas by staff. Administrators have the ability to grant editall+ privileges to other editors and to approve new directory-wide policies, authorities that had previously only been available to root (staff) editors.[11] A full list of senior editors is available to the public. [8]

All ODP editors are expected to abide by ODP's Editing Guidelines.[9] These guidelines describe editing basics: what types of sites may be listed and which may not; how site listings should be titled and described in a loosely consistent manner; conventions for the naming and building of categories; conflict of interest limitations on the editing of sites which the editor may own or otherwise be affiliated with; and a code of conduct within the community. Editors who are found to have violated these guidelines may be contacted by staff or senior editors, have their editing permissions cut back, or lose their editing privileges entirely. ODP Guidelines are periodically revised after discussion in editor forums.

Site submissions

One of the original motivations for forming Gnuhoo/Newhoo/ODP was the frustration that many people experienced in getting their sites listed on Yahoo! Directory. However Yahoo! has since implemented a paid service for timely consideration of site submissions. That lead has been followed by many other directories. Some accept no free submission at all. By contrast the ODP has maintained its policy of free site submissions for all types of site — the only one of the major general directories to do so.

One result has been a gradual divergence between the ODP and other directories in the balance of content. The pay-for-inclusion model favours those able and willing to pay, so commercial sites tend to predominate in directories using it. (See for example the initial impact on Looksmart. [10]) Whereas a directory manned by volunteers will reflect the aims and interests of those volunteers. The ODP lists a high proportion of informational and non-profit sites.

Another consequence of the free submission policy is that the ODP has enormous numbers of submissions. The ODP now has approximately two million unreviewed submissions, in large part due to spam and incorrectly submitted sites.[citation needed] So the average processing time for a site submission has grown longer with each passing year. However the time taken cannot be predicted, since the variation is so great: a submission might be processed within hours or take several years.

Controversy and criticism

There have long been allegations that volunteer ODP editors give favorable treatment to their own websites while concomitantly thwarting the good faith efforts of their competition[11]. Such allegations are fielded by ODP's staff and meta editors, who have the authority to take disciplinary action against volunteer editors who are suspected of engaging in abusive editing practices. In 2003, ODP introduced a new Public Abuse Report System that allows members of the general public to report and track allegations of abusive editor conduct using an online form.[12] Other alleged abuses have occurred at the executive level, with company management leveraging the link value from ODP to accelerate new privately funded projects. Although site policies suggest that an individual site is submitted in only one category [12], Topix.net, a news aggregation site operated by ODP founder Rich Skrenta, has more than 10,000 listings.[13]

Early in the history of the ODP, its staff gave representatives of selected websites, such as Rolling Stone magazine, editing access at ODP in order to list many individual pages from those websites. The use of such professional content providers lapsed and the experiment has not been repeated.

Ownership and management

Underlying some controversy surrounding ODP is its ownership and management. Many of the original GnuHoo volunteers felt that they had been deceived into joining a commercial enterprise.[citation needed] Most of that controversy died down when the project was renamed NewHoo. Moreover, when Netscape acquired the project, renamed it ODP, and released ODP's content under an open content license, criticism of the ODP all but disappeared. However, as ODP's content became widely used by most major search engines and web directories, the issue of ODP's ownership and management resurfaced.

At ODP's inception, there was little thought given to the idea of how ODP should be managed, and there were no official forums, guidelines, or FAQs. In essence, ODP began as a free for all. Even after ODP set up its internal editor forums, many editors remained blissfully unaware that these forums existed until they were directed to the forums by one of their fellow editors. Moreover, given that ODP had no official guidelines at first, ODP editors simply hashed out some sort of consensus among themselves and published unofficial FAQs.

As time went on, the ODP Editor Forums became the de facto ODP parliament, and when one of ODP's staff members would post an opinion in the forums, it would be considered an official ruling. (In other words, "Staff has spoken.") There was also a short-lived attempt at moderation of the ODP Editor Forums, but it was abandoned as being the antithesis of the egalitarian principles on which the ODP community was supposed to be based. Even so, ODP staff began to give trusted senior editors additional editing privileges, including the ability to approve new editor applications, which eventually led to a stratified hierarchy of duties and privileges among ODP editors, with ODP's paid staff having the final say regarding ODP's policies and procedures.

Allegations that editors are removed for criticizing policies

ODP's paid staff has imposed controversial policies from time to time[citation needed], and volunteer editors who dissent in ways staff considers uncivil may find their editing privileges removed.[citation needed] One alleged example of this was chronicled at the XODP Yahoo! eGroup in May of 2000.[13] The earliest known exposé was Life After the Open Directory Project, later appearing as a June 1, 2000, guest column written for Traffick.com,[14] by David F. Prenatt, Jr. (former ODP editor "netesq") after losing his ODP editing privileges. Another example was the volunteer editor known by the alias The Cunctator, who was banned from the ODP soon after submitting an article to Slashdot on October 24, 2000, which criticized changes in ODP's copyright policies.[15]

Uninhibited discussion of ODP's purported shortcomings has become more common on mainstream Webmaster discussion forums.[citation needed]

Editor removal procedures

ODP's editor removal procedures are overseen by ODP's staff and meta editors. According to ODP's official editorial guidelines, editors are removed for abusive editing practices or uncivil behaviour. Discussions that may result in disciplinary action against volunteer editors take place in a private forum which can only be accessed by ODP's staff and meta editors, and volunteer editors who are being discussed are not given notice that such proceedings are taking place. Some people find this arrangement distasteful, wanting instead a discussion modeled more like a trial held in the U.S. judicial system.

In the article Editor Removal Explained, ODP meta editor Arlarson states that "a great deal of confusion about the removal of editors from ODP results from false or misleading statements by former editors".[16]

ODP has a standing policy that prohibits any current ODP editors in a position to know anything from discussing the reasons for specific editor removals. In the past, this has led to claims that many ODP editors are left to wonder why they cannot login at ODP to perform their editing work.[citation needed]

However, ODP is now set up in such a way that when someone attempts to login at ODP using a deactivated editor login, a generic web page is displayed that informs a removed editor that a final decision has been made regarding the deactivation of his or her login and providing a list of possible reasons as to why such a decision might have been made.[citation needed]

Blacklisting allegations

Senior ODP editors have the ability to attach "warning" or "do not list" notes to individual domains, but no editor has the unilateral ability to block certain sites from being listed. Sites with these notes might still be listed, and at times notes are removed after some discussion.


The ODP Editor Forums were originally run on software that was based on the proprietary Ultimate Bulletin Board system. In June 2003, they switched to the open source phpBB system. As of 2007, these forums are powered by a modified version of phpBB.

The ODPSearch software is a derivative version of Isearch and is open source, licensed under the Mozilla Public License.

The bug tracking software used by the ODP is Bugzilla, and the web server Apache. Squid web proxy server is also used, all these applications being open source.

However, the ODP database/editing software is closed source, although Richard Skrenta of ODP did say in June 1998 that he was considering licensing it under the GNU General Public License. This has led to criticism from the aforementioned GNU project and other proponents of free software[citation needed], many of whom also criticise the ODP content license.[17]

As such, there have been some efforts to provide alternatives to ODP (see below). These alternatives would allow communities of like-minded editors to set up and maintain their own open source/open content Web directories. However, no significant open source/open content alternative to ODP has emerged.

Hierarchical structure

There recently is criticism of ODP's hierarchical structure. Many believe hierarchical directories are too complicated. As the recent emergence of Web 2.0, folksonomies began to appear. These people thought folksonomies, networks, and directed graph are more "natural" and easier to manage than hierarchies.[18][19][20]

See also


  1. ^ "The GnuHoo BooBoo". Slashdot. Retrieved on April 27, 2007.
  2. ^ ODP Front Page, retrieved 15 August 2006
  3. ^ Open Directory Forum - General - Analyzing editor numbers - page 1, 13 August 2006
  4. ^ "Dmoz's Catastrophic Server/Hardware Failure" October 27, 2006, retrieved November 15, 2006
  5. ^ "dmoz.org technical problems (UPDATED: December 18, 2006)", Resource-Zone.com Announcement, retrieved December 19, 2006
  6. ^ dmoz.org technical problems (UPDATED: January 13, 2007) at resource-zone.com
  7. ^ The Hamsters' New Home, in: Open Directory newsletter issue Winter 2006, retrieved December 26, 2006
  8. ^ Kids and Teens Launches! Open Directory Project Newsletter, November/December 2000
  9. ^ Communication and Codes of Conduct: Using the Forums, from the Open Directory Editing Guidelines
  10. ^ Communication and Codes of Conduct: Email and Forum Privacy, from the Open Directory Editing Guidelines
  11. ^ Open Directory Project Administrator Guidelines
  12. ^ Open Directory Project: Public Abuse Report System.
  13. ^ XODP Yahoo! Group Message Archive
  14. ^ David F. Prenatt, Jr., Life After the Open Directory Project, Traffick.com (June 1, 2000).
  15. ^ CmdrTaco, Dmoz (aka AOL) Changing Guidelines In Sketchy Way, Slashdot (October 24, 2000).
  16. ^ Arlarson, Editor Removal Explained, Open Directory Project Newsletter (September 2000).
  17. ^ "The primary problems are that your right to redistribute any given version is not permanent and that it requires the user to keep checking back at that site, which is too restrictive of the user's freedom." http://www.fsf.org/licensing/licenses/index_html#NonFreeDocumentationLicenses
  18. ^ Hriţcu, C., Folksonomies vs. Ontologies, 8th April 2005.
  19. ^ Shirky, C., Ontology is Overrated: Links, Tags, and Post-hoc Metadata, ITConversations, 15th March 2005.
  20. ^ Hammond, T., Hannay, T., Lund, B. & Scott, J., Social Bookmarking Tools (I) D-Lib Magazine, April 2005.

External links

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