The UN/EDIFACT standards
As said in the UN/EDIFACT article, the standards for the EDIFACT messages are defined and maintained by work groups at the UN.
The standards are released every year, mostly at spring. The standards are backward compatible which means that new standards does not make standards of previous years invalid. A message structure of D93A is still valid, even we have the D04A standard released. Modifications on existing messages are mostly additions to the existing structures and are mostly conditional.
Qualifiers and qualifier values
There are some difficulties regarding the qualifiers. Especially for older standards (D95A and older) there are either incomplete or no code list files. To show a complete site, we show all qualifiers of the selected standard and values of the most recent service code list if the required definitions are not available in the selected standard.
That is, for example in D95A, the values for the qualifier 0065 (Message types) are retrieved from the service code lists (released 2004). In most of the other standards the definitions are complete and we need not to fall back on the actual service code list files. You can see that in looking on the qualifier lists, too. In D95A, the list starts with qualifier 1001, while the list of D04A starts with 0001.