Issues Concerning Entity Comparison

Some systems do not use unique piece marks. On import, piece mark values are transferred to the :SDNFEMARK UDA field. When SDNF exports them, the application reference number is put into the :SDNFMARK UDA field. Theoretically, if these are unique between and within each system, then SDNF can cross refer the members between packages. However, some packages (XSteel, for example) do not use unique piece marks and can lead to multiple instances of the same piece mark within the imported model. It then becomes impossible to use :SDNFMARK as a unique pointer to the incoming member. Therefore, repeated imports and merging from other packages into the application and comparing the differences produces wrong results. In fact, subsequent merging of the models produce drastically wrong results. Using the memberID as an identifier is also not reliable as this value is really dependent upon the sequence of export from the other package. There is no other attribute or flag that can be used to uniquely identify members in this situation. Trying to use member position as an additional discriminator would actually hide differences, and not be any better.

The problem is impossible to solve. When repeatedly importing into the application, the best practice is to delete the old structure, or find some way to merge them.

The practice applies to both linear and plate members.