A Federated Wiki is a new type of distributed wiki. It's hosted, edited, administrated and operated in a part-decentralized way by it's users. It's federated like Diaspora (or other Federated Social Networks). It has asynchronous and (soon) real-time text editing, a distributed conflict management system, like the ability to fork, branch and merge pages and so on. Federated Wikis redefine how we publish, edit, host and administrate text document type pages (and potentially other types of data). They are a step closer to P2P Wiki(s).
Joining a federated wiki is as easy as email. Just choose a wiki website/federated wiki provider you like, create an account and start using it. Another option is be a provider yourself; just install the software and run it on a server. To that degree, federated wikis are still centralized. The key to understanding how federated wikis work is that page changes can be pushed or pulled cross-wiki. All wikis involved in the federation can share changes to pages.
The software was created by Wiki inventor, Ward Cunningham and others. From Ward Cunningham's GitHub:
"We imagine two components:
1. a server component managing page storage and collaboration between peer servers, and, 2. a client component presenting and modifying the server state in server specific ways.
This project should be judged by the degree that it can:
Demonstrate that wiki would have been better had it been effectively federated from the beginning. Explore federation policies necessary to sustain an open creative community."
One could potentially apply the ideas to blogs, Federated Blog(s). One can modify say, Wordpress, to federate blog posts and comments cross-blogosphere. It can be seen as a generalization of the concept of RSS, but with read and write capabilities. And supporting several other protocols, among other things, would have to take place to bridge the gap to connect federated blogs to federated wiki and the federated web generally.