Termination w.r.t. Q of the given QTRS could be disproven:

(0) Obligation:

Q restricted rewrite system:
The TRS R consists of the following rules:

a(l(x1)) → l(a(x1))
r(a(x1)) → a(r(x1))
b(l(x1)) → b(a(r(x1)))
r(b(x1)) → l(b(x1))

Q is empty.

(1) NonTerminationProof (EQUIVALENT transformation)

We used the non-termination processor [OPPELT08] to show that the SRS problem is infinite.

Found the self-embedding DerivationStructure:

b (a)^k l b → b (a)^k+1 l b

b (a)^k l b → b (a)^k+1 l b
by Overlap u with r (ol3)

b (a)^k l → b (a)^k+1 r
by Overlapping Derivationstructures

b (a)^k l → b a r (a)^k
by Overlap u with l (ol4)

(a)^k l → l (a)^k
by Selfoverlapping OC am1

a l → l a
by original rule (OC 1)

b l → b a r
by original rule (OC 1)

r (a)^k → (a)^k r
by Selfoverlapping OC am2

r a → a r
by original rule (OC 1)

r b → l b
by original rule (OC 1)

(2) NO