(0) Obligation:

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

a(a(x)) → b(b(x))
b(b(a(x))) → a(b(b(x)))

Q is empty.

(1) DependencyPairsProof (EQUIVALENT transformation)

Using Dependency Pairs [AG00,LPAR04] we result in the following initial DP problem.

(2) Obligation:

Q DP problem:
The TRS P consists of the following rules:

A(a(x)) → B(b(x))
A(a(x)) → B(x)
B(b(a(x))) → A(b(b(x)))
B(b(a(x))) → B(b(x))
B(b(a(x))) → B(x)

The TRS R consists of the following rules:

a(a(x)) → b(b(x))
b(b(a(x))) → a(b(b(x)))

Q is empty.
We have to consider all minimal (P,Q,R)-chains.

(3) QDPOrderProof (EQUIVALENT transformation)

We use the reduction pair processor [LPAR04].


The following pairs can be oriented strictly and are deleted.


A(a(x)) → B(b(x))
A(a(x)) → B(x)
B(b(a(x))) → B(b(x))
B(b(a(x))) → B(x)
The remaining pairs can at least be oriented weakly.
Used ordering: Polynomial interpretation [POLO]:

POL(A(x1)) = 1 + x1   
POL(B(x1)) = x1   
POL(a(x1)) = 1 + x1   
POL(b(x1)) = x1   

The following usable rules [FROCOS05] were oriented:

b(b(a(x))) → a(b(b(x)))
a(a(x)) → b(b(x))

(4) Obligation:

Q DP problem:
The TRS P consists of the following rules:

B(b(a(x))) → A(b(b(x)))

The TRS R consists of the following rules:

a(a(x)) → b(b(x))
b(b(a(x))) → a(b(b(x)))

Q is empty.
We have to consider all minimal (P,Q,R)-chains.

(5) DependencyGraphProof (EQUIVALENT transformation)

The approximation of the Dependency Graph [LPAR04,FROCOS05,EDGSTAR] contains 0 SCCs with 1 less node.

(6) TRUE