today, it's impossible to find the unsecured JBossAS servers.  if groups could be filtered by unset/null properties, then the user could do something like:

empty resource.pluginConfiguration[principal]
resource.type.plugin = JBossAS
resource.type.name = JBossAS Server

since 'empty' is a type of reference comparison (as opposed to value comparison), might as well support the 'not empty' construct at the same time.  thus, the 3 supported major syntax variants would then be:

"condition = value"
"groupBy condition"
"(not) empty condition" // 'not' is optional