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A MOO ("MUD, object-oriented"[1][2]) is a text-based online virtual reality system to which multiple users (players) are connected at the same time.

The term MOO is used in two distinct, but related, senses. One is to refer to those programs descended from the original MOO server, and the other is to refer to any MUD that uses object-oriented techniques to organize its database of objects, particularly if it does so in a similar fashion to the original MOO or its derivatives. Most of this article refers to the original MOO and its direct descendants, but see non-descendant MOOs for a list of MOO-like systems.

The original MOO server was authored by Stephen White, based on his experience from creating the programmable TinyMUCK system.[3][2] There was additional later development and maintenance from LambdaMOO founder, and former Xerox PARC employee, Pavel Curtis.

One of the most distinguishing features of a MOO is that its users can perform object-oriented programming within the server, ultimately expanding and changing how it behaves to everyone.[4] Examples of such changes include authoring new rooms and objects, creating new generic objects for others to use, and changing the way the MOO interface operates. The programming language used for extension is the MOO programming language, and many MOOs feature convenient libraries of verbs that can be used by programmers in their coding known as Utilities. The MOO programming language is a domain-specific language.[citation needed]


MOOs are network accessible, multi-user, programmable, interactive systems well-suited to the construction of text-based adventure games, conferencing systems, and other collaborative software. Their most common use, however, is as multi-participant, low-bandwidth virtual realities. They have been used in academic environments for distance education, collaboration (such as Diversity University), group decision systems,[5] and teaching object-oriented concepts;[6] but others are primarily social in nature, or used for role-playing video games, or simply to take advantage of the programming possibilities. They have also been used in scientific studies of virtual presence.[7][8][9]

Most commonly, MOOs are connected to by users using a client which speaks the telnet protocol, which provides a stay-alive connection with the host, to relay output and send commands. Some however have developed web interfaces, or other such methods; however this commonly limits interaction that the user can have, usually to the point they have no interaction, but instead can browse objects and discover typical information. Developments in cross-MOO networking have also led to the creation of SunNET, a hubless network allowing cross-MOO communication and add extra possibilities to cross-MOO development, including networked channels. Another network called GNA-NET, designed by Gustavo Glusman of BioMOO connected seventeen mostly education sites. Most of these MOOs hosted online classes or other early versions of distance education.[10][11]

Every MOO stores the content and state of all its objects within a persistent object database, which keeps objects from being lost by a reset of the MOO server software or the computer hosting it.

New MOOs have to choose a starting database from which to set their MOO up, or they can use a minimal one which contains only the necessary objects to start a MOO. There are a handful of such MOO "core" databases which serve as foundations of code and utilities from which to start your MOO, including LambdaCore (from LambdaMOO), MinimalDB (considered the minimum necessary code and utilities to work usefully in a MOO), JHCore (from Jay's House Moo), and enCore (from LinguaMOO).

Every object in the MOO is assigned a number, and may be referred to by this number, prefixed with a #, as well as its name when the user is in the object's presence. Administrators, also known as wizards, who can manage the MOO, and assign certain global names to these objects, which are prefixed with $, a process known as corifying. They also feature parenting systems, and every object will have a parent, commonly eventually leading to Root Class, otherwise known as #1. #0 is also reserved as a special system object which is responsible for managing the list of global names, incoming network connections, and other information related to the operation of the system.


MOO, along with all of its nephews, started out with text based adventure games. With the advent of the internet, MUD was formed as a networked version of one of those games. Eventually it developed into a tree of different types of MUD, with MOO becoming one of them.

Stephen White (also known by the handles "Ghondahrl" and "ghond") wrote the first version of the MOO server, which was released on May 2, 1990, and used for the operation of a server called "AlphaMOO". Pavel Curtis, an employee of Xerox PARC and also known by his handles "Lambda", and "Haakon", took the basic design, language, and code, fixed bugs and added features to release the second version, called "LambdaMOO" on October 30, 1990.

According to Jill Serpentelli in her paper Conversational Structure and Personality Correlates of Electronic Communication:

Curtis went on to explain how the transition occurred from AlphaMOO to LambdaMOO. After fixing bugs in the system, rewriting some of the code, adding more programming capability, and writing documentation, he had created what he termed "a truly separate entity" from the original AlphaMOO. He dubbed this new system LambdaMOO, after one of his names on the system and, according to Curtis, "because it's a key word in some of the other non-mud research that I do." The new system was announced as open for public access on UseNet (a world-wide bulletin board system) in February 1991 (Curtis, personal communication).[12]

MOO was originally developed as a MUD server in the same general style (sharing much of the command syntax and community conventions) as TinyMUD.

There are currently[when?] two distributions of the MOO server code. The more popular of the two, the LambdaMOO server, is named such as indication of the close historical and continuing association of the MOO server code with the first public MOO, LambdaMOO.

The LambdaMOO version of MOO that gained popularity in the early 1990s, and it remains[as of?] the most widely used MOO distribution. Pavel Curtis continued to maintain the server for several years. Other early contributors to the LambdaMOO server included users Tim Allen ("Gemba"), "Gary_Severn", Roger Crew ("Rog"), Judy Anderson ("yduJ"), and Erik Ostrom (known as "Joe Feedback"). Later, Erik Ostrom maintained the server, and the server is now maintained by Ben Jackson and Jay Carlson and has a LambdaMOO project.

Social behavior on MOOs

Behavior on social MOOs and role-playing MOOs has been shown to differ. For example, an early study looked at whether users engaged in gender-switching (that is, adopting a different gender online). The majority of participants (60 percent) in social MOOs had never engaged in gender-switching, while the majority (56.7 percent) in role-playing MOOs had done so. However, most of those engaged in gender-switching did so on average only 10 percent of the time. The study also found that the primary barrier to gender-switching was the belief that it is dishonest and manipulative.[13]

Current projects based on MOO

This section is about an event or subject that may not be current but does not specify the time period. Please help improve it to include this information. The talk page may contain suggestions. (December 2022)

Non-descendant MOOs

Some servers use "MOO" style object-oriented characteristics without being descended from the original MOO server, in the sense that they use little or none of that server's source code and use internal languages that are more or less incompatible with the MOO programming language. None of them have attained the popularity of LambdaMOO or its relatives.[citation needed]

Stephen White went on to write a new and similar system called CoolMUD, although it never obtained the same wide userbase as MOO. Another, later, attempt at a programmable object-oriented MUD server was ColdMUD, written by Greg Hudson and later maintained by Brandon Gillespie under the name "Genesis".[14]

One unusual MOO with no real relationship to the original MOO is called mooix. mooix is unique among MUDs in that it uses the underlying UNIX operating system to handle all of the multitasking and networking issues. Several unique side effects result from this, one of which is that the MOO can be programmed in any language. mooix was written after a failed attempt by Joey Hess to write a MOO entirely in Perl, called perlmoo.[15]


Participants (usually referred to as users) connect to a MOO using telnet or some other, more specialized, client program. Upon connection, they are usually presented with a welcome message explaining how to either create a new character or connect to an existing one.

Almost every command is parsed by the server into a call on a MOO procedure, or verb, which actually does the work. Thus, programming in the MOO programming language is a central part of making non-trivial extensions to the database and hence the virtual reality.[citation needed]


All MOOs provide a flag called Wizard; when set on a player, the player gains the ability to view and modify nearly everything in the MOOs database. Such players usually form the basis for MOO administration. Designated owners of a MOO are sometimes referred to as Archwizards.

These wizards can restrict access to the MOO, as well as make news postings and monitor logs. Wizard permissions are needed for modification and even execution of verbs and properties for which the user does not own, or is not publicly readable/writable. All verbs and properties within objects have the appropriate flags, with the user can change to determine its current state.

Notable examples

This section needs to be updated. Please help update this article to reflect recent events or newly available information. (December 2022)

Social MOOs

Research MOOs

Educational MOOs

MOO games

See also


  1. ^ Shah, Rawn; Romine, James (1995). Playing MUDs on the Internet. John Wiley & Sons, Inc. p. 238. ISBN 0-471-11633-5. For example, the MOO (Muds Object-Oriented) is a direct result of work in this area.
  2. ^ a b Taylor, T.L. (2006-02-24). Play Between Worlds: Exploring Online Game Culture. The MIT Press. pp. 23. ISBN 0262201631.
  3. ^ Bartle, Richard (2003). Designing Virtual Worlds. New Riders. p. 11. ISBN 0-13-101816-7. One player, Stephen White, decided in 1990 to extend the functionality of TinyMUD and write TinyMUCK (muck being a kind of mud). Using this as his template, he then produced MOO (MUD, Object Oriented).
  4. ^ Bartle, Richard (2003). Designing Virtual Worlds. New Riders. p. 11. ISBN 0-13-101816-7. MOO introduced a fully functional scripting language (as such in-world programming languages are called) and thus brought the LPC-like capabilities to social-oriented virtual worlds.
  5. ^ Evard, R. (1993, November) Collaborative networked communication: MUDS as systems tools. Proceedings of the Seventh Systems Administration Conference (LISA VII), pp. 1-8, Monterey, CA.
  6. ^ Towell, JF (2000) MOO: An active-learning environment for teaching object-oriented concepts in business information systems curricula, Journal of Information Systems Education, 11(304) 147-150.
  7. ^ Towell, JF, & Towell, ER (1997). Presence in text-based networked virtual environments or "MUDS," Presence: Teleoperators and Virtual Environments 6(5) 590-595.
  8. ^ Shiano, DJ (1999). Lessons from LambdaMOO: A social, text-based virtual environment, Presence: Teleoperators and Virtual Environments 8(2), 127-139 article Archived 2015-05-14 at the Wayback Machine.
  9. ^ Towell, JF & Towell, ER (2001) 34th Meetings of the Hawaii International Conference on Systems Science (HICSS-34), Maui, Hawaii.
  10. ^ "The GNA Network". 2011-07-24. Archived from the original on 2011-07-24. Retrieved 2020-07-19.
  11. ^ "Projet staf14: Distance education on WWW". 2010-05-30. Archived from the original on 2010-05-30. Retrieved 2020-07-19.
  12. ^ "Conversational Structure and Personality Correlates of Electronic Communication". Electronic Frontier Foundation. 2007-09-26. Archived from the original on 2007-09-26. Retrieved 2020-07-19.
  13. ^ Roberts, Lynne D.; Parks, Malcolm R. (1999). "The social geography of gender-switching in virtual environments on the Internet". Information, Communication & Society. 2 (4): 521. doi:10.1080/136911899359538.
  14. ^ Bartle, Richard (2003). Designing Virtual Worlds. New Riders. p. 11. ISBN 0-13-101816-7. MOO had two important offspring: Pavel Curtis' LambdaMOO (which was to become a favorite of journalists, academics, and social misfits) and, via CoolMUD, ColdMUD (an attempt to create a software-engineering quality virtual world authoring system).
  15. ^ "perlmoo". 2007-02-18. Archived from the original on 2007-02-18. Retrieved 2020-07-19.
  16. ^ "LambdaMOO (with LambdaMOO Map) An Introduction -". 2005-12-18. Archived from the original on 2005-12-18. Retrieved 2020-07-19.
  17. ^ Riddle, Prentiss (1993-04-13). "GopherCon '93: Internet Gopher Workshop and Internet Gopher Conference". Retrieved 2008-05-20.
  18. ^ "What's New! June 1993". Netscape Corporation. 1993-06-24. Retrieved 2008-05-20.
  19. ^ Hand, Chris (1994). "meet me in cyberspace".
  20. ^ "FactoryNET Prospectus". 1998-12-05. Archived from the original on 1998-12-05. Retrieved 2020-07-19.[unreliable source?]
  21. ^ "EFF & Aerosmith Rock the Net - Update - Where/When/How". 2011-09-27. Archived from the original on 2011-09-27. Retrieved 2020-07-19.
  22. ^ LaFarge, Antoinette. "Towards an Id Theater". Plaintext Players.
  23. ^ "SchoolNetMOO Lesson Plan" [1] 14 August 1998
  24. ^ Carton, Sean (1995). Internet Virtual Worlds Quick Tour. Ventana Press. p. 165. ISBN 1-56604-222-4. What began as an experiment in text-based virtual reality has become the hangout for a virtual who's who of media researchers. The MediaMOO is an online recreation of MIT's Media Lab, and it's populated exclusively by people interested in the future of interactive communication, alternative media and virtual reality.
  25. ^ PMC2 Archives
  26. ^ De Cicco, Eta; Farmer, Mike; Hargrave, Claire (1999). Activities for Using the Internet in Primary School. Routledge. ISBN 0-7494-2989-5.
  27. ^ Bruckman, Amy. MOOSE Crossing: Construction, Community, and Learning in a Networked Virtual World for Kids (Ph.D thesis). MIT Media Lab.
  28. ^ "1999 Young Innovator: Amy Bruckman". Technology Review. MIT. November 1999. Retrieved 2007-10-10.
  29. ^ "MOOSECrossing". 2007-05-07. Archived from the original on October 12, 2009. Retrieved 2010-04-22.
  30. ^ Flusfeder, Helena (1996-11-08). "Life mutates in MOO dimension". Retrieved 2008-12-16.
  31. ^ Anderson, Christopher "Cyberspace Offers Chance To Do 'Virtually' Real Science" 264, 900-901, Science, 1994.
  32. ^ Towell, John Foster, Hansen, Paul, Mercer, Eric, Leach, Martin, Rubin, Irit, Prilusky, Jaime & Glusman, Gustavo (1995, November). Networked virtual environments and electronic conferencing. In S.M. Bachrach, D.B. Boyd, S.K. Gray, W. Hase, and H. Rzepa (Ed.), Proceedings of the First Electronic Computational Chemistry Conference [CD-ROM]. ARInternet: Landower, MD.
  33. ^ Hardy BH, Robinson A, Doughty S, Findsen LA, Towell ER, Towell JF, and Wilson IBH (1996, January) A new direction in conferencing: the First Electronic Glycoscience Conference, Trends in Biochemical Sciences, 21(1), 31-33.
  34. ^ "BioMOO announce VR web interface". 1995-04-30. Retrieved 2008-12-16.
  35. ^ Fuellen, Georg. "GNA's Virtual School of Natural Sciences". Archived from the original on 2008-06-12.
  36. ^ "FUP server builtin functions". 1997-04-17. Retrieved 2008-12-16.
  37. ^ "Login (LinguaMOO)". 2005-12-15. Archived from the original on 2005-12-15. Retrieved 2005-12-01.
  38. ^ Haynes, CA & Holmevik JR (1999) MOOniversity: A Student's Guide to Online Learning Environments, Longman, ISBN 0-205-27114-6
  39. ^ Haynes, CA & Holmevik JR (2001) High Wired: On the Design, Use, and Theory of Educational MOOs, University of Michigan Press, ISBN 0-472-08838-6
  40. ^ Sant, Toni and Flintoff, Kim. [2], 24 July 2007. Retrieved on 29 October 2012.
  41. ^ "ATHEMOO Basic Information" [3] 28 October 2012
  42. ^ Schrum, Stephen. "Theatre in Cyberspace", Pg 112 Peter Lang Publishing, New York, 1999.