MAYBE
Input TRS:
      1: a(b(x1)) -> c(d(x1))
      2: d(d(x1)) -> b(e(x1))
      3: b(x1) -> d(c(x1))
      4: d(x1) -> x1
      5: e(c(x1)) -> d(a(x1))
      6: a(x1) -> e(d(x1))
Number of strict rules: 6
Direct POLO(bPol) ... failed.
Uncurrying ... failed.
Dependency Pairs:
     #1: #d(d(x1)) -> #b(e(x1))
     #2: #d(d(x1)) -> #e(x1)
     #3: #a(x1) -> #e(d(x1))
     #4: #a(x1) -> #d(x1)
     #5: #e(c(x1)) -> #d(a(x1))
     #6: #e(c(x1)) -> #a(x1)
     #7: #b(x1) -> #d(c(x1))
     #8: #a(b(x1)) -> #d(x1)
Number of SCCs: 1, DPs: 6
  SCC { #2..6 #8 }
POLO(Sum)... POLO(max)... QLPOS... POLO(mSum)... QWPOpS(mSum)... Mat2b... failed.
Finding a loop...  failed.