@henridf suggested having type IDs available to zql (e.g., to do count() by id(fld)), but since they are arbitrary integers this would an odd semantics. So, instead we could have first-class types in zng where typeof(fld) is a type value that images the same as a zng type string but is a bona fide value in the zq runtime.

This could be encoded as a type ID in the zng binary format.

The zng spec needs to be updated along with the addition of the zng type type to package zng and handling for the type in the zq runtime.