The parallel wiki takes the idea of BrainstormMode and turns it into something larger. On the parallel wiki, you can have as many brainstorm pages as you require to express your new idea. Having more pages to develop ideas is also an instance of the EnlargeSpace pattern.
Be sure to understand what a parallel wiki is all about: In fact this is about creating a border to be understood and respected by members and visitors. This may be beneficial or not. If the original wiki contains "official and high quality content" and the parallel wiki represents the "editorial system", there is a production process, a workflow. Therefore, the editorial wiki becomes the real community wiki where the traffic goes and where the interesting discussions are.
If the parallel wiki is only about getting rid of off-topic content, there should be simpler ways -- just make wiki space as accessible as possible. Give it away or sell it cheap, and make the difference between on-topic and off-topic content clear.
See also DoubleWiki
A parallel wiki doesn't need technology to support it. CommunityExpectation can make it clear that new and unpolished content go to the parallel wiki, first.
In order to keep the parallel wiki close to the original, several techniques have been proposed.
Well, MetaWikiPedia seems to be a parallel wiki, but neither the site nor the content is ephemeral. And yet it serves to brainstorm and enlarge space. I therefore changed "less structured and ephemeral" to "less structured or ephemeral". -- AlexSchroeder
It's important to note that MetaWikiPedia was created to move undesirables away from the main project (see MetaWikiPedia), and SpaghettiWiki was proposed here for the same reason. ParallelWiki is probably an AntiPattern. See the discussion on EnlargeSpace about pushing away undesirables. -- SunirShah
I think that one should be very clear about the reason and the goal of a ParallelWiki. In fact this is about creating a border (just like OT) which is assumed to be understood and respected by members and visitors. Borders may have positive or negative effects, depending on the circumstances. One could for example think about the main wiki as "official and high quality content" and about the parallel wiki as "editorial system". In this case there is a production process and a workflow. If it works that way, the editorial wiki becomes the real community wiki where the traffic goes and where the interesting discussions are. If the parallel wiki is only about getting rid of OT content, there should be simpler ways - just make wiki space as accessible as possible. Give it away or sell it cheap. That's the way I typically go. And make the OT borders and regulations as clean as possible. -- HelmutLeitner
I also agree with Bayle and Helmut and I am an advocate of RadicalInclusiveness, something JohnAbbe passed along to me, so in that vain, I have trouble placing people in the category of undesireable. Maybe if we are specific about WhoIsUndesireable?, I would feel more comfortable with the discussion. I admit that I do not have the vast online experience that many members of this community have, however, I do know that in community building (in meat space) having the lowest entry barrier possible (while still maintaining your mission) is the best possible situation. MarkDilley
How would, say, the international WikiPedia wikis factor in here? Are they parallel? Also, what about the danger of attention drain? That work, effort, attention done on the original wiki is drained off to the parallel one? --EvanProdromou
Nice idea, but I'd prefer every topic to be a namespace of its own - i.e. recursable. TWiki has webs - so it would be like this except that every topic could contain a web, ad infinitum. -- MartinCleaver