wiki on a specific subject is to follow the wiki-node network from wiki to wiki. Participants The four basic types of users who participate in wikis are reader, author, wiki administrator and system administrator. The system administrator is responsible for the installation and maintenance of the wiki engine and the container web server. The wiki administrator maintains wiki content and is provided additional functions about pages (e.g. page protection and deletion), and can adjust users' access rights by, for instance, blocking them from editing. Growth factors A study of several hundred wikis showed that a relatively high number of administrators for a given content size is likely to reduce growth; that access controls restricting editing to registered users tends to reduce growth; that a lack of such access controls tends to fuel new user registration; and that higher administration ratios (i.e. admins/user) have no significant effect on content or population growth. Conferences Active conferences and meetings about wiki-related topics include: Atlassian Summit, an annual conference for users of Atlassian software, including Confluence. OpenSym (called WikiSym until 2014), an academic conference dedicated to research about wikis and open collaboration. SMWCon, a bi-annual conference for users and developers of Semantic MediaWiki. TikiFest, a frequently held meeting for users and developers of Tiki Wiki CMS Groupware. Wikimania, an annual conference dedicated to the research and practice of Wikimedia Foundation projects like Wikipedia. Former wiki-related events include: RecentChangesCamp (2006–2012), an unconference on wiki-related topics. RegioWikiCamp (2009–2013), a semi-annual unconference on "regiowikis", or wikis on cities and other geographic areas. Legal environment Joint authorship of articles, in which different users participate in correcting, editing, and compiling the finished product, can also cause editors to become tenants in common of the copyright, making it impossible to republish without permission of all co-owners, some of whose identities may be unknown due to pseudonymous or anonymous editing. Where persons contribute to a collective work such as an encyclopedia, there is, however, no joint ownership if the contributions are separate and distinguishable. Despite most wikis' tracking of individual contributions, the action of contributing to a wiki page is still arguably one of jointly correcting, editing, or compiling, which would give rise to joint ownership. Some copyright issues can be alleviated through the use of an open content license. Version 2 of the GNU Free Documentation License includes a specific provision for wiki relicensing; Creative Commons licenses are also popular.