Two `aberrant' semantic features were identified by Petra Barg as being different from some established usages, for example the Düsseldorf QDATR implementation. The first concerns undefined paths (where ZDATR V 1.0 and V1.01 returned the null value), and other DATR implementations return a designated atom such as '!_UNDEFINED_!'. We have changed the implementation here. The second concerns the ZDATR `atom overrides variable' principle, which we have not changed. We give our reasons below.