Certification Problem

Input (COPS 1036)

We consider the TRS containing the following rules:

c(c(x)) b(b(x)) (1)
a(a(x)) b(a(x)) (2)
c(c(x)) a(a(x)) (3)
b(b(x)) c(b(x)) (4)
b(c(x)) a(c(x)) (5)
a(a(x)) a(a(x)) (6)
a(a(x)) b(c(x)) (7)
b(c(x)) b(a(x)) (8)
a(a(x)) c(b(x)) (9)
b(b(x)) c(c(x)) (10)
c(b(x)) c(c(x)) (11)
a(c(x)) b(c(x)) (12)
c(b(x)) a(c(x)) (13)
b(b(x)) b(b(x)) (14)
c(b(x)) b(c(x)) (15)
b(c(x)) b(c(x)) (16)
c(a(x)) a(a(x)) (17)
a(c(x)) c(a(x)) (18)
a(b(x)) a(a(x)) (19)

The underlying signature is as follows:

{c/1, b/1, a/1}

Property / Task

Prove or disprove confluence.

Answer / Result

Yes.

Proof (by csi @ CoCo 2023)

1 Redundant Rules Transformation

To prove that the TRS is (non-)confluent, we show (non-)confluence of the following modified system:

a(b(x)) a(a(x)) (19)
a(c(x)) c(a(x)) (18)
c(a(x)) a(a(x)) (17)
c(b(x)) b(c(x)) (15)
c(b(x)) a(c(x)) (13)
a(c(x)) b(c(x)) (12)
c(b(x)) c(c(x)) (11)
b(b(x)) c(c(x)) (10)
a(a(x)) c(b(x)) (9)
b(c(x)) b(a(x)) (8)
a(a(x)) b(c(x)) (7)
b(c(x)) a(c(x)) (5)
b(b(x)) c(b(x)) (4)
c(c(x)) a(a(x)) (3)
a(a(x)) b(a(x)) (2)
c(c(x)) b(b(x)) (1)

All redundant rules that were added or removed can be simulated in 1 steps .

1.1 Redundant Rules Transformation

To prove that the TRS is (non-)confluent, we show (non-)confluence of the following modified system:

a(b(x)) a(a(x)) (19)
a(c(x)) c(a(x)) (18)
c(a(x)) a(a(x)) (17)
c(b(x)) b(c(x)) (15)
c(b(x)) a(c(x)) (13)
a(c(x)) b(c(x)) (12)
c(b(x)) c(c(x)) (11)
b(b(x)) c(c(x)) (10)
a(a(x)) c(b(x)) (9)
b(c(x)) b(a(x)) (8)
a(a(x)) b(c(x)) (7)
b(c(x)) a(c(x)) (5)
b(b(x)) c(b(x)) (4)
c(c(x)) a(a(x)) (3)
a(a(x)) b(a(x)) (2)
c(c(x)) b(b(x)) (1)
a(b(x)) c(b(x)) (20)
a(b(x)) b(c(x)) (21)
a(b(x)) b(a(x)) (22)
a(c(x)) a(a(x)) (23)
c(a(x)) c(b(x)) (24)
c(a(x)) b(c(x)) (25)
c(a(x)) b(a(x)) (26)
c(b(x)) b(a(x)) (27)
c(b(x)) c(a(x)) (28)
a(c(x)) b(a(x)) (29)
a(c(x)) a(c(x)) (30)
c(b(x)) a(a(x)) (31)
c(b(x)) b(b(x)) (32)
b(b(x)) a(a(x)) (33)
b(b(x)) b(b(x)) (14)
a(a(x)) a(c(x)) (34)
a(a(x)) c(c(x)) (35)
b(c(x)) c(a(x)) (36)
b(c(x)) b(c(x)) (16)
b(b(x)) b(c(x)) (37)
b(b(x)) a(c(x)) (38)
c(c(x)) c(b(x)) (39)
c(c(x)) b(c(x)) (40)
c(c(x)) b(a(x)) (41)
c(c(x)) c(c(x)) (42)

All redundant rules that were added or removed can be simulated in 2 steps .

1.1.1 Redundant Rules Transformation

To prove that the TRS is (non-)confluent, we show (non-)confluence of the following modified system:

c(c(x)) b(a(x)) (41)
c(c(x)) b(c(x)) (40)
c(c(x)) c(b(x)) (39)
b(b(x)) a(c(x)) (38)
b(b(x)) b(c(x)) (37)
b(c(x)) c(a(x)) (36)
a(a(x)) c(c(x)) (35)
a(a(x)) a(c(x)) (34)
b(b(x)) a(a(x)) (33)
c(b(x)) b(b(x)) (32)
c(b(x)) a(a(x)) (31)
a(c(x)) b(a(x)) (29)
c(b(x)) c(a(x)) (28)
c(b(x)) b(a(x)) (27)
c(a(x)) b(a(x)) (26)
c(a(x)) b(c(x)) (25)
c(a(x)) c(b(x)) (24)
a(c(x)) a(a(x)) (23)
a(b(x)) b(a(x)) (22)
a(b(x)) b(c(x)) (21)
a(b(x)) c(b(x)) (20)
c(c(x)) b(b(x)) (1)
a(a(x)) b(a(x)) (2)
c(c(x)) a(a(x)) (3)
b(b(x)) c(b(x)) (4)
b(c(x)) a(c(x)) (5)
a(a(x)) b(c(x)) (7)
b(c(x)) b(a(x)) (8)
a(a(x)) c(b(x)) (9)
b(b(x)) c(c(x)) (10)
c(b(x)) c(c(x)) (11)
a(c(x)) b(c(x)) (12)
c(b(x)) a(c(x)) (13)
c(b(x)) b(c(x)) (15)
c(a(x)) a(a(x)) (17)
a(c(x)) c(a(x)) (18)
a(b(x)) a(a(x)) (19)

All redundant rules that were added or removed can be simulated in 1 steps .

1.1.1.1 Redundant Rules Transformation

To prove that the TRS is (non-)confluent, we show (non-)confluence of the following modified system:

c(c(x)) b(a(x)) (41)
c(c(x)) b(c(x)) (40)
c(c(x)) c(b(x)) (39)
b(b(x)) a(c(x)) (38)
b(b(x)) b(c(x)) (37)
b(c(x)) c(a(x)) (36)
a(a(x)) c(c(x)) (35)
a(a(x)) a(c(x)) (34)
b(b(x)) a(a(x)) (33)
c(b(x)) b(b(x)) (32)
c(b(x)) a(a(x)) (31)
a(c(x)) b(a(x)) (29)
c(b(x)) c(a(x)) (28)
c(b(x)) b(a(x)) (27)
c(a(x)) b(a(x)) (26)
c(a(x)) b(c(x)) (25)
c(a(x)) c(b(x)) (24)
a(c(x)) a(a(x)) (23)
a(b(x)) b(a(x)) (22)
a(b(x)) b(c(x)) (21)
a(b(x)) c(b(x)) (20)
c(c(x)) b(b(x)) (1)
a(a(x)) b(a(x)) (2)
c(c(x)) a(a(x)) (3)
b(b(x)) c(b(x)) (4)
b(c(x)) a(c(x)) (5)
a(a(x)) b(c(x)) (7)
b(c(x)) b(a(x)) (8)
a(a(x)) c(b(x)) (9)
b(b(x)) c(c(x)) (10)
c(b(x)) c(c(x)) (11)
a(c(x)) b(c(x)) (12)
c(b(x)) a(c(x)) (13)
c(b(x)) b(c(x)) (15)
c(a(x)) a(a(x)) (17)
a(c(x)) c(a(x)) (18)
a(b(x)) a(a(x)) (19)
c(c(x)) c(a(x)) (43)
c(c(x)) a(c(x)) (44)
c(c(x)) c(c(x)) (42)
b(b(x)) b(a(x)) (45)
b(b(x)) c(a(x)) (46)
b(c(x)) b(c(x)) (16)
b(c(x)) c(b(x)) (47)
b(c(x)) a(a(x)) (48)
a(a(x)) b(b(x)) (49)
a(a(x)) a(a(x)) (6)
a(a(x)) c(a(x)) (50)
c(b(x)) c(b(x)) (51)
c(a(x)) c(a(x)) (52)
c(a(x)) a(c(x)) (53)
c(a(x)) b(b(x)) (54)
c(a(x)) c(c(x)) (55)
a(c(x)) c(c(x)) (56)
a(c(x)) a(c(x)) (30)
a(c(x)) c(b(x)) (57)
a(b(x)) c(a(x)) (58)
a(b(x)) a(c(x)) (59)
a(b(x)) b(b(x)) (60)
a(b(x)) c(c(x)) (61)
b(b(x)) b(b(x)) (14)

All redundant rules that were added or removed can be simulated in 2 steps .

1.1.1.1.1 Strongly closed

Confluence is proven since the TRS is strongly closed. The joins can be performed using 7 step(s).