MAYBE
af/ONE-SORTED/33.trs
Input rules:
   [ f(a) -> f(g(b,b)),
     a -> g(c,c),
     c -> d,
     d -> b,
     b -> d ]
Sorts having no ground terms: 
Rules applicable to ground terms:
   [ f(a) -> f(g(b,b)),
     a -> g(c,c),
     c -> d,
     d -> b,
     b -> d ]
Constructor pattern: [g(?x_1,?x_2)]
Defined pattern: [d,c,b,a,f(?x_1)]
Constructor subsystem:
   [ ]
Modified Constructor subsystem:
   [ ]
candidate for d:
   [ d -> b ]
candidate for c:
   [ c -> d ]
candidate for b:
   [ b -> d ]
candidate for a:
   [ a -> g(c,c) ]
No orientable rules for f(?x_1). Add rules, and retry...
failed to construct defining rules
Retry with a different D/C-partition.
Constructor pattern: [g(?x_1,?x_2),f(?x_1)]
Defined pattern: [d,c,b,a]
Constructor subsystem:
   [ ]
Modified Constructor subsystem:
   [ ]
candidate for d:
   [ d -> b ]
candidate for c:
   [ c -> d ]
candidate for b:
   [ b -> d ]
candidate for a:
   [ a -> g(c,c) ]
Find a quasi-ordering ...
encodeSameNthStatus g/0, g/1
encodeSameNthStatus(sub) logArF:1, logArG:1
failed to find an ordering.
Try to supplement auxiliary rules.
{f(g(b,b))}{}{}{}{}Supplemented Rules:
   [ ]
failed to supplement auxiliary rules
check Non-Ground-Confluence...
ground constructor terms for instantiation: {}
ground terms for instantiation: {a:o}
obtain 12 rules by 3 steps unfolding
obtain 98 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)
(538 msec.)
1.96