Notice: Use of undefined constant …

Notice: Use of undefined constant …

This kind of message appears because SMW namespace constants (SMW_NS_PROPERTY, SMW_NS_TYPE and SMW_NS_CONCEPT) are delayed due to the parameter $smwgNamespaceIndex being a prerequisite and its initialization has to happen first it can be processed. To resolve this you have to add

enableSemantics( 'example.org' );

prior to any parameter (e.g. $wgContentNamespaces, $wgNamespacesToBeSearchedDefault and $wgNamespaceProtection) making reference to these namespace constants. In case you choose to manually set $smwgNamespaceIndex to something other than the default value of 102, you must do this above the enableSemantics() call.