- third letter
+b: "big tree" reduction
c: conversion
d: decomposed extended reduction
+e: decomposed extended conversion
q: restricted reduction
r: reduction
s: substitution
- forth letter (if present)
-p: non-reflexive transitive closure (plus)
-q: reflexive closure (question)
-s: reflexive transitive closure (star)
+e: reflexive transitive closure to normal form (evaluation)
+p: non-reflexive transitive closure (plus)
+q: reflexive closure (question)
+s: reflexive transitive closure (star)