https://msdn.microsoft.com/en-us/library/gg328549.aspx https://msdn.microsoft.com/en-us/library/gg328549.aspx SDK https://msdn.microsoft.com/en-us/library/gg328549.aspx Activity Party http://msdn.microsoft.com/en-us/library/gg328549.aspx http://msdn.microsoft.com/en-us/library/gg328549.aspx ActivityParty entity ActivityParty entity Activity Party in the SDK