...
The Any wildcard (i.e. *) should be able to be used to represent any concrete value (i.e. number or string), rather than just for any concept. In doing so, consideration must be given to ensure that the grammar is unambiguous in its parse tree. One option could be to force A = #* for numeric wildcards and A="*" for string wildcards. Other options will also be consideredable to be parsed unambiguously.