Does it
matter, whether eClass 4 is mapped to eClass5 or the other way
around? Yes, it does
matter. This shall be explained with a small example: eClass 4 class
01-02-03-99 has been split in: eClass 5
class 01-02-03-01 eClass 5
class 01-02-03-02 eClass 5
class 01-02-03-03 eClass 5
class 01-02-03-04
Then a mapping
from eClass 5 to eClass 4 could work automatically (all projects, which
use one of the four eClass 5 classes are classified to the one eClass 4
class). But a mapping
from eClass 4 to eClass 5 would not work, because the mapper does not
know, which of the four classes should be taken. In order to
solve theses cases, the mappings from eClass 5 -> eClass 4 and eClass
4 -> eClass 5 are two different mappings. | 
![[Note]](images/note.png)