The subscriptions element contains one or more subscription elements.
adapter                                   (required, limit one)
  |----rfa                                (required, limit one)
  '----subscriptions                      (required, limit one)
         '----subscription                (required)
                '----stream               (required)
                       |----name          (required, limit one)
                       |----service       (optional)
                       |      '----enum   (required)
                       |----stale         (optional)
                       |----field         (required)
                       '----constant      (optional)
adapter
| Name | Requirement | 
|---|---|
| Subscription | One or more | 
None
Each subscription instance in this section defines one set of data that the adapter publishes to RMDS.
See the example for an individual subscription instance.