Like distributed computing, reflection is also work in progress and will be added soon*.
Reflection allows you to get the provenance of a value as another value. This means you can get the full computational history of an (immutable) value, plus all the associated (immutable) code that produced the value - as a data structure that can be further operated on.
This self reflection - or provenance capability - has many interesting applications, mostly related to distributed trust and security. An efficient implementation of such capability is a challenge, but has already been proven to be feasible in the SPREAD framework by the same author of ALT.