[yang-doctors] QQ on mandatory statement

[Mahesh Jethanandani <[e-mail]>]

I have a quick question about the use of a mandatory statement. draft-ietf-ccamp-optical-impairment-topology-yang-23 <https://datatracker.ietf.org/doc/html/draft-ietf-ccamp-optical-impairment-topology-yang-23> includes this mandatory choice statement, where the model ensures that one of the cases is selected in the config. However, the model defines two case statements, each with a leaf that also has a mandatory statement. I realize that the ABNF grammar does not explicitly prohibit it, but ...

Having a mandatory statement under choice would be sufficient. When would one need to define a mandatory statement under each of the cases, when both the case statements have a single leaf? Isn’t the mandatory choice satisfied since one of the leaf types has to be defined in the config tree?


          container power-param {
            description
              "Amplifier elements typically equalize the optical
               power across the amplified channels using one of the
               available equalization strategies - either targeting
               a specific output power, or a specific power spectral
               density (PSD), after the out-voa.";
            choice power-param {
              mandatory true;
              description
                "Select the mode: channel power or power spectral
                 density (PSD).";
              case channel-power {
                leaf nominal-carrier-power {
                  type l0-types:power-dbm-or-unknown;
                  mandatory true;
                  description
                    "Reference channel power.";
                }
              }
              case power-spectral-density {
                leaf nominal-psd {
                  type l0-types:psd-or-unknown;
                  mandatory true;
                  description
                    "Reference power spectral density (PSD).";
                }
              }
            }
          } // container power-param

Thanks in advance.

Mahesh Jethanandani
[e-mail]