This is just a brainstorm, which I hope someone will look into more deeply.
- >x> is "and"
- | is "or"
- <x< is "cut" (more on this later)
Orc's evaluation order is breadth-first rather than depth-first like Prolog. In many scenarios we are only interested in the first solution (first publication), so depth-first evaluation is more efficient (this exact idea is explored in Deparallelization).
and: >x>, or: |#
Ignoring cut, the logical meaning of these combinators is obvious.
Prolog's cut operator (!) prevents backtracking. Since Orc's evaluation is breadth-first no direct translation is possible, but there is a rough analogy. "F <x< G" evaluates F with only the first possible value of G, just as G, !, F does.