OpenSimulator is an open source multi-platform, multi-user 3D application server. It can be used to create a virtual environment (or world) which can be accessed through a variety of clients, on multiple protocols.
The idea behind APML is to compress all forms of attention data into a portable file format containing a description of the user's rated interests.
Can XMPP be used for gaming purposes?
Can this be used to synchronize information between games?
Resource Description Framework (RDF)
Web Ontology Language (OWL)
Simple Knowledge Organization System (SKOS)