Since the beginning of the ABINIT HTML documentation, every input variable has been required to belong to a “varset” (set of variables, e.g. varbas, varfil, …).
However, starting in Summer 2017, we require every input variable to be also mentioned in at least one of the documentation “topics” and, for such topic, to be characterized by a “relevance”.

The allowed list of relevances (a generic list, irrespective of the topic) is contained in the file ~abinit/doc/topics/origin_files/list_relevances.yml . Standard names are:

1. “compulsory” (when such input variable MUST be present in the input file when the “feature” of the topic is activated);
2. “basic” (when such input variable is usually explicitly specified in the standard usage, although the default might be adequate);
3. “useful” (when the default value is used most of the time);
4. “expert” (when only expert users should use other values than the default).
   

Other relevance names have been allowed for specific topics, in which such a classification (compulsory/basic/useful/expert) is not an adequate one.

In order to specify the (possibly several) combinations of topic+relevance to which an input variable is rattached, the field “topics” is used inside the ~abinit/doc/input_variables/generated_doc/abinit_vars.yml file (and can be filled thanks to the use of the Abivars.jar GUI).

Some examples …

• for dmatpawu : “DFT+U_useful”
• for mdwall : “MolecularDynamics_expert”
• for gwpara : “parallelism_useful, GW_basic”.
  

The latter is a case where one input variable is associated to two topics, with a different relevance for topic “parallelism” and topic “GW”.