World Theory


define: virtual world

The term virtual world can be difficult to grap, therefore a definition is needed...

Last update: 2007-06-22T23Z

The term virtual world has grown out of the term virtual reality, thus signifying something that presents itself with traits from the physical world, but doesn't exist as a physical entity, typically mediated by a computer.

This view is too limiting and arbitrary. A more abstract defintion is needed. The following is a temporary definition, I'll come up with a better one later.

virtual world
A virtual world is a computer-mediated reality which presents the user with an experience which can be reasoned about as if it is a world, but the represenation of that world is not required to be analog to a possible physical alternative.
A world is an environment that is intuitively interpreted by most human-beings as an interconnected collection of places which have qualities that can be found in the habitats of human beings. One important quality is the ability to choose where to go and what to do.
multi-user virtual world
A multi-user virtual world is a virtual world centered around interaction between multiple users.

Alternative list of properties

Although I think the previous definitions are sufficient a tighter list of core properties for online virtual worlds might come in handy. The following is based on the properties I used in my 1999 report (Design av virtuelle flerbrukerverdener for fritidsbruk, section 3.1):

  • The system provides a geographic environment where the user can discern between here and there.

  • The system provides the user with decent support for orientation and movement.

  • The user experiences high levels of interaction with the world and other users.

  • The user has a sense of being able to affect the world.

  • The user experiences a strong sense of taking initiative in relation to the system.

  • The user experiences a continuous existence crossing a series of sessions, while mediating a stable identity to other users.

  • The system constitutes a coherent vision.

Not all virtual worlds will provide all the properties, but if they do, they certainly qualifies for the label online virtual world.

Discussion and examples

There is a great variety of virtual worlds. They can be single-user simulations of historical sites or simulated walk-throughs of urban designs. They can be real-time or not. They may be recreational or not. They may include gaming aspects, or not.

Important: Often the term virtual world is used to mean a real-time multi-user virtual world. However, qualities such as having multiple simultanous users are volatile, at some points in time there are no users.

Because of the wide connotations of the term world, the term virtual world has to be understood in context. Usually you can deduce from the context what it is meant to cover. There are plenty of examples of how a narrow interpretation of the term keeps causing confusion. A recent discussion is the confusion about whether a game is a virtual world and the term has been discussed at length on the mailinglist mud-dev in 2004.

Related terms

Other terms have been used that have a lot of overlap with the term virtual world. One of the earliest terms was MUD after Richard Bartle et al's MUD1, often taken as an acronym for Multi-User Dungeon or Multi-User Domain. Another early term used by VR researchers is the term CVE an abbreviation for Collaborative Virtual Environments, usually used to signify 3D VR-like applications for serious uses rather than gaming. More recent and widespread terms come from the gaming communities: MMORPG stands for Massively Multi-player Online Role-Playing Game and MMOG/MMO stands for Massively Multi-player Online Game.

Of course there are a bunch of other terms that have been used to described similar phenomena, as I wrote on mud-dev in 1999:


shared virtual reality (shared VR)
Used by the VR community to describe VR with multiple participants.
shared spaces
Used by authors discussing general problems, such as temporal aspects, which are relevant for all spatial multiuser systems.
collaborative virtual environment (CVE)
Used by the spatial oriented branch of computer supported cooperative work (CSCW) with links to the VR community.
multi user dimension (MUD)
Used by those who have a background in textual multiuser systems with links back to Mud1. Originally known as "multi user dungeon".
multi user virtual environment (MUVE)
Not too common, probably used to distinguish their work as more serious than what most MUDs are.
multi user adventure (MUA)
I think this was introduced to avoid the confusion between the term MUD and the game MUD. Didn't succeed.
multi user game (MUG)
I believe I used to see this term quite a lot in the late 80s.
multi player online game (MPOG)
Used by those that came to the field through singleuser games which were turned into "few-player" multiplayer games. Often simple peer-to-peer systems.
massive multi player online game (MMPOG)
Used by those who use the term MPOG. It basically means the same as MUD, but as those systems which are described as MPOGs typically have a large commercial entrprise behind them, they are expected to cater for thousands of users.
virtual world
Used by those who think about their system as a graphical avatar space, where users is living in a habitat. Typically these systems is more oriented towards the surface than mechanics. Unfortunately this term is heavily used in other fields as well, for instance as a general term which to describe hypotetical avant garde 3D models in architecture.
collaborative virtual world (CVW)
Used by the same guys who are likely to use the term CVE. It is used to describe spaces which is less bent towards CSCW, and more towards creating an experiental world.


virtual reality
Yes, this term has in fact been used to describe even text-only MUDs. Probably because of the high hype factor...
multi user game world
gaming world
Rare. (I believe Bruce Damer/CCON use it)
online role playing game (ORPG)
massive online role playing game (MORPG)
Used by those who try to avoid what might be associated by MUD and MPOG.
Not a stand alone term. Usually used in a context where virtual and multiuser is assumed. Decends from Habitat/WorldsAway.
virtual space
Yet another term used to describe MUDs and similar systems.
virtual community
Generally used for all types of online community like systems, but also used as a reference to MUDs by some authors.
multi user player-extensible game (MUPEG)
See Bartle's MUDReport.

Of course, this is list is not complete. Raph Koster provides some other terms on his blog. Here is a selection from his blog-entry:

Online game
a game played using network connectivity.
Online virtual world
a simulation of persistent space connected to via a network, wherein users are represented by proxies often terms avatars. Note thatboth “online” and “virtual” are often elided from the term.
Synthetic world
see online virtual world.
the hypothetical idea that online virtual worlds would be linked together to form a single network.
Mirror world
an online virtual world that mirrors data from the real world.

There are also some additional terms coined by non-gamers who are discontent with being associated with virtual worlds as gaming-platforms, and vice versa. One such term is social worlds, which is basically a misnomer as almost all virtual worlds are social and have some users who primarily socialize... Thus it essentially describes a lack of games rather than a presence of social features.