Certain special properties are built-in to Semantic MediaWiki to make the system work. See the Annotation help page for more information. They appear in a page's factbox in italic. You should not use these reserved names for your own properties.
The pages listed below on wiki.nycresistor.com provide documentation for Semantic MediaWiki's special properties, but are not required; a special property will have special behavior even if your wiki does not have a property page for it.
Confusingly, these built-in special properties do not appear in the Special:Properties page that lists all user-created properties in use in the wiki.