EssencePrime is a constraint specification language. The language was originally designed as a subset of ESSENCE, but now has language features which are not in ESSENCE, such as matrix comprehension.
The main feature missing from EssencePrime which is in ESSENCE is high-level types, EssencePrime contains only integers, Booleans and matrices of these types.
There is one actively maintained implementation of EssencePrime:
There is one inactive implementation of EssencePrime