The open-space meeting or open space meeting is a generic term describing a wide variety of different styles of meeting in which participants define the agenda with a relatively rigorous process, and may adjust it as the meeting proceeds. A large meeting of this sort is called an open space conference or unconference.
All the variants, and the original Open Space Technology that gave this meeting system its name, require that individuals participate without prior groupings or agendas, and that they accept the agendas and groupings that arise from the meeting process, with only minimal restrictions on scope. Since 1986 the movement has been associated with Harrison Owen. (The specific original OST is described in the Open Space Technology article. This one is concerned with the generic adaptations, some of which vary in scope from Owen's methods.)
More conventional variations allow prior restrictions on scope, agenda, and groupings, e.g. couples or interest groups or tendency or factions or even formal parties. These are not considered genuine by promoters of the pure original open-space concept as being likely to sanctify groupthink. Any such structure imposes some precedent ideas of the subject matter, since 'existing discourses' are being imported and can continue within the conference, e.g. two people who agree on a matter strongly can all attend the same sub-circles and continue to back each other up, reducing the chance that either of them will learn anything, or that anyone can learn anything from them. These more conventional variations or hybrids are however sometimes easier to gain management or participant support for.
Because it requires that all participants contribute to the definition of scope, the general agenda, the specific agendas guiding the sub-groups or sub-circles (an essential feature of the original Open Space Technology which cannot by definition be held all in the same room with all participants), OST can be considered a variation of a WikiWiki.
This aspect of producing collective text, e.g. as is done in treaty negotiation, is a major purpose of many such meetings. However, the scheduling of sub-circles in parallel or in series, determining what circles one must ignore to pursue others, is a major difference: there is no requirement in any form of WikiWiki that contributors to one aspect of a text forgo contributing to others. This is, however, considered to be a main feature of OST, that sessions run in parallel and involve only those most deeply concerned.
The Living Agenda variant of an open space meeting uses wikis to define agendas and distribute minutes. It abandons many of the psychological elements of the original OST.