MAYBE
af/ONE-SORTED/649.trs
Input rules:
   [ a -> a,
     b -> h(f(f(f(b))),h(b,f(a))) ]
Sorts having no ground terms: 
Rules applicable to ground terms:
   [ a -> a,
     b -> h(f(f(f(b))),h(b,f(a))) ]
Constructor pattern: [h(?x_1,?x_2),f(?x_1)]
Defined pattern: [b,a]
Constructor subsystem:
   [ ]
Modified Constructor subsystem:
   [ ]
No orientable rules for b. Add rules, and retry...
failed to construct defining rules
Retry with a different D/C-partition.
Constructor pattern: [h(?x_1,?x_2),f(?x_1),b]
Defined pattern: [a]
Constructor subsystem:
   [ ]
Modified Constructor subsystem:
   [ ]
No orientable rules for a. Add rules, and retry...
failed to construct defining rules
Retry with a different D/C-partition.
Constructor pattern: [h(?x_1,?x_2),f(?x_1),b,a]
Defined pattern: []
Constructor subsystem:
   [ a -> a,
     b -> h(f(f(f(b))),h(b,f(a))) ]
a -> a
{}
   [  ]
Modified Constructor subsystem:
   [ b -> h(f(f(f(b))),h(b,f(a))) ]
Find a quasi-ordering ...
encodeSameNthStatus h/0, h/1
encodeSameNthStatus(sub) logArF:1, logArG:1
failed to find an ordering.
Try to supplement auxiliary rules.
{a}{b}Supplemented Rules:
   [ ]
failed to supplement auxiliary rules
check Non-Ground-Confluence...
ground constructor terms for instantiation: {}
ground terms for instantiation: {a:o}
obtain 10 rules by 3 steps unfolding
obtain 0 candidates for checking non-joinability
check by TCAP-Approximation (failure)
check by Ordering(rpo), check by Tree-Automata Approximation (failure)
check by Interpretation(mod2) (failure)
check by Descendants-Approximation, check by Ordering(poly) (failure)
: Failure(unknown)
(27 msec.)
0.04