In , people mentioned key descriptor might not be required for use cases in SESSION table function. For example, the SESSION table function can directly be applied on a data from a website. Technically there is still a key, but just all data have the same website key.
There are three options to make key descriptor "optional"
1) make key descriptor optional.
2) accept empty descriptor.
3) descriptor becomes nullable.
I am planning to try 1) first.