What is tkind?

I was looking through
https://github.com/githwxi/ATS-Postiats/blob/master/libats/SATS/gnode.sats,
and there is this definition:

sortdef tk = tkind

What is tkind sort for?

tkind is like ‘type’; it is algebraic (that is, not involving quantifiers).

The plan i to use tkind to support a more flexible/powerful way of template
instantiation.On Saturday, March 1, 2014 3:32:06 AM UTC-5, Artyom Shalkhakov wrote:

I was looking through
https://github.com/githwxi/ATS-Postiats/blob/master/libats/SATS/gnode.sats,
and there is this definition:

sortdef tk = tkind

What is tkind sort for?