[xwiki-users] Workspace Users not found

Hello everybody, Here is my problem : I'm in a workspace. I've created a class with a database list field. I've written the HQL query : -> select obj.name from BaseObject obj where obj.className='XWiki.XWikiUsers' And when i'm in edit mode, the suggest says me : "no results !" when i'm writing a username. I wonder if this problem is related to the difference between local users (= workspace users ?) and global users (= wiki users ?). Thanks for your attention M.Canzerini