On the Two Short Axiomatizations of Ortholattices

by
Wioletta Truszkowska, and

Copyright (c) 2003 Association of Mizar Users

MML identifier: ROBBINS2
[ MML identifier index ]

```environ

vocabulary LATTICES, SUBSET_1, ARYTM_3, ROBBINS1, ROBBINS2;
notation STRUCT_0, LATTICES, ROBBINS1;
constructors REALSET1, ROBBINS1;
clusters ROBBINS1;
theorems ROBBINS1, LATTICES, REALSET1;

begin :: One Axiom for Boolean Algebra

definition let L be non empty ComplLattStr;
attr L is satisfying_DN_1 means :Def1:
for x, y, z, u being Element of L holds
(((x + y)` + z)` + (x + (z` + (z + u)`)`)`)` = z;
end;

definition
cluster TrivComplLat -> satisfying_DN_1;
coherence
proof
let x, y, z, u be Element of TrivComplLat;
thus thesis by REALSET1:def 20;
end;
cluster TrivOrtLat -> satisfying_DN_1;
coherence
proof
let x, y, z, u be Element of TrivOrtLat;
thus thesis by REALSET1:def 20;
end;
end;

definition
cluster join-commutative join-associative satisfying_DN_1
(non empty ComplLattStr);
existence
proof
take TrivComplLat;
thus thesis;
end;
end;

reserve L for satisfying_DN_1 (non empty ComplLattStr);
reserve x, y, z, u, v for Element of L;

theorem Th1: :: A61
for L being satisfying_DN_1 (non empty ComplLattStr),
x, y, z, u, v being Element of L holds
((x + y)` + (((z + u)` + x)` + (y` + (y + v)`)`)`)` = y
proof
let L be satisfying_DN_1 (non empty ComplLattStr);
let x, y, z, u, v be Element of L;
set X = ((z + u)` + x)`, Y = (z + (x` + (x + u)`)`)`;
set Z = y, U = v;
(((X + Y)` + Z)` + (X + (Z` + (Z + U)`)`)`)` = Z by Def1;
hence thesis by Def1;
end;

theorem Th2: :: A62
for L being satisfying_DN_1 (non empty ComplLattStr),
x, y, z, u being Element of L holds
((x + y)` + ((z + x)` + (y` + (y + u)`)`)`)` = y
proof
let L be satisfying_DN_1 (non empty ComplLattStr);
let x, y, z, u be Element of L;
consider v being Element of L;
((x + z)` + (((y + u)` + x)` + (z` + (z + v)`)`)`)` = z by Th1;
hence thesis by Th1;
end;

theorem Th3: :: A63
for L being satisfying_DN_1 (non empty ComplLattStr),
x being Element of L holds
((x + x`)` + x)` = x`
proof
let L be satisfying_DN_1 (non empty ComplLattStr);
let x be Element of L;
consider y, u being Element of L;
set V = (x + u)`;
((x + x`)` + (((x`` + y)` + x)` + (x`` + (x` + V)`)`)`)` = x` by Th1;
hence thesis by Def1;
end;

theorem Th4: :: A64
for L being satisfying_DN_1 (non empty ComplLattStr),
x, y, z, u being Element of L holds
((x + y)` + ((z + x)` + (((y + y`)` + y)` + (y + u)`)`)`)` = y
proof
let L be satisfying_DN_1 (non empty ComplLattStr);
let x, y, z, u be Element of L;
((y + y`)` + y)` = y` by Th3;
hence thesis by Th2;
end;

theorem Th5: :: A65
for L being satisfying_DN_1 (non empty ComplLattStr),
x, y, z being Element of L holds
((x + y)` + ((z + x)` + y)`)` = y
proof
let L be satisfying_DN_1 (non empty ComplLattStr);
let x, y, z be Element of L;
consider u being Element of L;
set U = (y` + (y + u)`)`;
((x + y)` + ((z + x)` + (((y + y`)` + y)` + (y + U)`)`)`)` = y by Th4;
hence thesis by Def1;
end;

theorem Th6: :: A66
for L being satisfying_DN_1 (non empty ComplLattStr),
x, y being Element of L holds
((x + y)` + (x` + y)`)` = y
proof
let L be satisfying_DN_1 (non empty ComplLattStr);
let x, y be Element of L;
set Z = (x + x`)`;
((x + y)` + ((Z + x)` + y)`)` = y by Th5;
hence thesis by Th3;
end;

theorem Th7: :: A67
for L being satisfying_DN_1 (non empty ComplLattStr),
x, y being Element of L holds
(((x + y)` + x)` + (x + y)`)` = x
proof
let L be satisfying_DN_1 (non empty ComplLattStr);
let x, y be Element of L;
set X = (x + y)`;
((X + x)` + ((x + X)` + (((x + x`)` + x)` + (x + y)`)`)`)` = x by Th4;
hence thesis by Th5;
end;

theorem Th8: :: A68
for L being satisfying_DN_1 (non empty ComplLattStr),
x, y being Element of L holds
(x + ((x + y)` + x)`)` = (x + y)`
proof
let L be satisfying_DN_1 (non empty ComplLattStr);
let x, y be Element of L;
set X = (x + y)`, Y = x;
(((X + Y)` + X)` + (X + Y)`)` = X by Th7;
hence thesis by Th7;
end;

theorem Th9: :: A69
for L being satisfying_DN_1 (non empty ComplLattStr),
x, y, z being Element of L holds
(((x + y)` + z)` + (x + z)`)` = z
proof
let L be satisfying_DN_1 (non empty ComplLattStr);
let x, y, z be Element of L;
set X = (x + y)`, Y = z, Z = ((x + y)` + x)`;
((X + Y)` + ((Z + X)` + Y)`)` = Y by Th5;
hence thesis by Th7;
end;

theorem Th10: :: A70
for L being satisfying_DN_1 (non empty ComplLattStr),
x, y, z being Element of L holds
(x + ((y + z)` + (y + x)`)`)` = (y + x)`
proof
let L be satisfying_DN_1 (non empty ComplLattStr);
let x, y, z be Element of L;
set Z = (y + x)`, X = (y + z)`, Y = x;
(((X + Y)` + Z)` + (X + Z)`)` = Z by Th9;
hence thesis by Th9;
end;

theorem Th11: :: A71
for L being satisfying_DN_1 (non empty ComplLattStr),
x, y, z being Element of L holds
((((x + y)` + z)` + (x` + y)`)` + y)` = (x` + y)`
proof
let L be satisfying_DN_1 (non empty ComplLattStr);
let x, y, z be Element of L;
set X = (x + y)`, Z = (x` + y)`, Y = z;
(((X + Y)` + Z)` + (X + Z)`)` = Z by Th9;
hence thesis by Th6;
end;

theorem Th12: :: A72
for L being satisfying_DN_1 (non empty ComplLattStr),
x, y, z being Element of L holds
(x + ((y + z)` + (z + x)`)`)` = (z + x)`
proof
let L be satisfying_DN_1 (non empty ComplLattStr);
let x, y, z be Element of L;
set Y = z, Z = ((y + x)` + (y + z)`)`;
(x + ((Y + Z)` + (Y + x)`)`)` = (Y + x)` by Th10;
hence thesis by Th10;
end;

theorem Th13: :: A73
for L being satisfying_DN_1 (non empty ComplLattStr),
x, y, z, u being Element of L holds
((x + y)` + ((z + x)` + (y` + (u + y)`)`)`)` = y
proof
let L be satisfying_DN_1 (non empty ComplLattStr);
let x, y, z, u be Element of L;
set U = ((u + z)` + (u + y)`)`;
((x + y)` + ((z + x)` + (y` + (y + U)`)`)`)` = y by Th2;
hence thesis by Th10;
end;

theorem Th14: :: A74
for L being satisfying_DN_1 (non empty ComplLattStr),
x, y being Element of L holds
(x + y)` = (y + x)`
proof
let L be satisfying_DN_1 (non empty ComplLattStr);
let x, y be Element of L;
set Z = y, X = x, Y = (y + x)`;
((Y + Z)` + (Z + X)`)` = y by Th7;
hence thesis by Th12;
end;

theorem Th15: :: A75
for L being satisfying_DN_1 (non empty ComplLattStr),
x, y, z being Element of L holds
(((x + y)` + (y + z)`)` + z)` = (y + z)`
proof
let L be satisfying_DN_1 (non empty ComplLattStr);
let x, y, z be Element of L;
set Y = ((x + y)` + (y + z)`)`;
(z + Y)` = (Y + z)` by Th14;
hence thesis by Th12;
end;

theorem Th16: :: A76
for L being satisfying_DN_1 (non empty ComplLattStr),
x, y, z being Element of L holds
((x + ((x + y)` + z)`)` + z)` = ((x + y)` + z)`
proof
let L be satisfying_DN_1 (non empty ComplLattStr);
let x, y, z be Element of L;
set X = ((x + y)` + x)`, Y = (x + y)`;
(X + Y)` = x by Th7;
hence thesis by Th15;
end;

theorem Th17: :: A77
for L being satisfying_DN_1 (non empty ComplLattStr),
x, y being Element of L holds
(((x + y)` + x)` + y)` = (y + y)`
proof
let L be satisfying_DN_1 (non empty ComplLattStr);
let x, y be Element of L;
set X = (x + y)`;
(X + ((X + x)` + y)`)` = y by Th5;
hence thesis by Th16;
end;

theorem Th18: :: A78
for L being satisfying_DN_1 (non empty ComplLattStr),
x, y being Element of L holds
(x` + (y + x)`)` = x
proof
let L be satisfying_DN_1 (non empty ComplLattStr);
let x, y be Element of L;
set X = (y + x)`;
(X + ((x` + y)` + (x` + X)`)`)` = x by Th13;
hence thesis by Th10;
end;

theorem Th19: :: A79
for L being satisfying_DN_1 (non empty ComplLattStr),
x, y being Element of L holds
((x + y)` + y`)` = y
proof
let L be satisfying_DN_1 (non empty ComplLattStr);
let x, y be Element of L;
(y` + (x + y)`)` = y by Th18;
hence thesis by Th14;
end;

theorem Th20: :: A80
for L being satisfying_DN_1 (non empty ComplLattStr),
x, y being Element of L holds
(x + (y + x`)`)` = x`
proof
let L be satisfying_DN_1 (non empty ComplLattStr);
let x, y be Element of L;
set Z = x`, X = y, Y = x;
(((X + Y)` + Z)` + (X + Z)`)` = Z by Th9;
hence thesis by Th19;
end;

theorem Th21: :: A81
for L being satisfying_DN_1 (non empty ComplLattStr),
x being Element of L holds
(x + x)` = x`
proof
let L be satisfying_DN_1 (non empty ComplLattStr);
let x be Element of L;
consider y being Element of L;
set Y = (y + x)`;
(x + (Y + x`)`)` = x` by Th20;
hence thesis by Th19;
end;

theorem Th22: :: A83
for L being satisfying_DN_1 (non empty ComplLattStr),
x, y being Element of L holds
(((x + y)` + x)` + y)` = y`
proof
let L be satisfying_DN_1 (non empty ComplLattStr);
let x, y be Element of L;
y` = (y + y)` by Th21
.= (((x + y)` + x)` + y)` by Th17;
hence thesis;
end;

theorem Th23: :: A85
for L being satisfying_DN_1 (non empty ComplLattStr),
x being Element of L holds
x`` = x
proof
let L be satisfying_DN_1 (non empty ComplLattStr);
let x be Element of L;
x`` = (((x + x`)` + x)` + x`)` by Th22
.= x by Th19;
hence thesis;
end;

theorem Th24: :: A86
for L being satisfying_DN_1 (non empty ComplLattStr),
x, y being Element of L holds
((x + y)` + x)`+ y = y``
proof
let L be satisfying_DN_1 (non empty ComplLattStr);
let x, y be Element of L;
(((x + y)` + x)` + y)`` = y`` by Th22;
hence thesis by Th23;
end;

theorem Th25: :: A87
for L being satisfying_DN_1 (non empty ComplLattStr),
x, y being Element of L holds
(x + y)`` = y + x
proof
let L be satisfying_DN_1 (non empty ComplLattStr);
let x, y be Element of L;
(x + y)`` = (y + x)`` by Th14
.= y + x by Th23;
hence thesis;
end;

theorem Th26: :: A88
for L being satisfying_DN_1 (non empty ComplLattStr),
x, y, z being Element of L holds
x + ((y + z)` + (y + x)`)` = (y + x )``
proof
let L be satisfying_DN_1 (non empty ComplLattStr);
let x, y, z be Element of L;
(x + ((y + z)` + (y + x)`)`)`` = (y + x)`` by Th10;
hence thesis by Th23;
end;

theorem Th27: :: A89
for L being satisfying_DN_1 (non empty ComplLattStr),
x, y being Element of L holds
x + y = y + x
proof
let L be satisfying_DN_1 (non empty ComplLattStr);
let x, y be Element of L;
x + y = (x + y)`` by Th23
.= y + x by Th25;
hence thesis;
end;

Lm1:
for L being satisfying_DN_1 (non empty ComplLattStr) holds
L is join-commutative
proof
let L;
for x, y holds x + y = y + x by Th27;
hence thesis by LATTICES:def 4;
end;

definition
cluster satisfying_DN_1 -> join-commutative (non empty ComplLattStr);
coherence by Lm1;
end;

theorem Th28: :: A90
for L being satisfying_DN_1 (non empty ComplLattStr),
x, y being Element of L holds
((x + y)` + x)` + y = y
proof
let L be satisfying_DN_1 (non empty ComplLattStr);
let x, y be Element of L;
((x + y)` + x)` + y = y`` by Th24;
hence thesis by Th23;
end;

theorem :: A91
for L being satisfying_DN_1 (non empty ComplLattStr),
x, y being Element of L holds
((x + y)` + y)`+ x = x by Th28;

theorem :: A92
for L being satisfying_DN_1 (non empty ComplLattStr),
x, y being Element of L holds
x + ((y + x)` + y)` = x by Th28;

theorem Th31: :: A93
for L being satisfying_DN_1 (non empty ComplLattStr),
x, y being Element of L holds
(x + y`)` + (y` + y)` = (x + y`)`
proof
let L be satisfying_DN_1 (non empty ComplLattStr);
let x, y be Element of L;
set X = (x + y`)`;
X + ((y + X)` + y)` = X by Th28;
hence thesis by Th20;
end;

theorem Th32: :: A94
for L being satisfying_DN_1 (non empty ComplLattStr),
x, y being Element of L holds
(x + y)` + (y + y`)` = (x + y)`
proof
let L be satisfying_DN_1 (non empty ComplLattStr);
let x, y be Element of L;
set X = (x + y)`, Y = y`;
X + ((Y + X)` + Y)` = X by Th28;
hence thesis by Th18;
end;

theorem :: A95
for L being satisfying_DN_1 (non empty ComplLattStr),
x, y being Element of L holds
(x + y)` + (y` + y)` = (x + y)` by Th32;

theorem Th34: :: A96
for L being satisfying_DN_1 (non empty ComplLattStr),
x, y being Element of L holds
((x + y`)`` + y)` = (y` + y)`
proof
let L be satisfying_DN_1 (non empty ComplLattStr);
let x, y be Element of L;
set Y = y`, Z = y;
(((x + Y)` + (Y + Z)`)` + Z)` = (Y + Z)` by Th15;
hence thesis by Th31;
end;

theorem Th35: :: A97
for L being satisfying_DN_1 (non empty ComplLattStr),
x, y being Element of L holds
((x + y`) + y)` = (y` + y)`
proof
let L be satisfying_DN_1 (non empty ComplLattStr);
let x, y be Element of L;
((x + y`)`` + y)` = (y` + y)` by Th34;
hence thesis by Th23;
end;

theorem Th36: :: A98
for L being satisfying_DN_1 (non empty ComplLattStr),
x, y, z being Element of L holds
((((x + y`) + z)` + y)` + (y` + y)`)` = y
proof
let L be satisfying_DN_1 (non empty ComplLattStr);
let x, y, z be Element of L;
((x + y`) + y)` = (y` + y)` by Th35;
hence thesis by Th9;
end;

theorem Th37: :: A99
for L being satisfying_DN_1 (non empty ComplLattStr),
x, y, z being Element of L holds
x + ((y + z)` + (y + x)`)` = y + x
proof
let L be satisfying_DN_1 (non empty ComplLattStr);
let x, y, z be Element of L;
x + ((y + z)` + (y + x)`)` = (y + x )`` by Th26;
hence thesis by Th23;
end;

theorem Th38: :: A100
for L being satisfying_DN_1 (non empty ComplLattStr),
x, y, z being Element of L holds
x + (y + ((z + y)` + x)`)` = (z + y)` + x
proof
let L be satisfying_DN_1 (non empty ComplLattStr);
let x, y, z be Element of L;
set Y = (z + y)`, Z = y`;
x + ((Y + Z)` + (Y + x)`)` = Y + x by Th37;
hence thesis by Th19;
end;

theorem :: A101
for L being satisfying_DN_1 (non empty ComplLattStr),
x, y, z being Element of L holds
x + ((y + x)` + (y + z)`)` = y + x by Th37;

theorem Th40: :: A102
for L being satisfying_DN_1 (non empty ComplLattStr),
x, y, z being Element of L holds
((x + y)` + ((x + y)` + (x + z)`)`)` + y = y
proof
let L be satisfying_DN_1 (non empty ComplLattStr);
let x, y, z be Element of L;
set Y = ((x + y)` + (x + z)`)`;
((y + Y)` + Y)`+ y = y by Th28;
hence thesis by Th37;
end;

theorem Th41: :: A103
for L being satisfying_DN_1 (non empty ComplLattStr),
x, y, z being Element of L holds
(((x + y`) + z)` + y)`` = y
proof
let L be satisfying_DN_1 (non empty ComplLattStr);
let x, y, z be Element of L;
(((x + y`) + z)` + y)` + (y` + y)` = (((x + y`) + z)` + y)` by Th32;
hence thesis by Th36;
end;

theorem Th42: :: A104
for L being satisfying_DN_1 (non empty ComplLattStr),
x, y, z being Element of L holds
x + ((y + x`) + z)` = x
proof
let L be satisfying_DN_1 (non empty ComplLattStr);
let x, y, z be Element of L;
(((y + x`) + z)` + x)`` = x by Th41;
hence thesis by Th25;
end;

theorem Th43: :: A105
for L being satisfying_DN_1 (non empty ComplLattStr),
x, y, z being Element of L holds
x` + ((y + x) + z)` = x`
proof
let L be satisfying_DN_1 (non empty ComplLattStr);
let x, y, z be Element of L;
set X = x`;
X + ((y + X`) + z)` = X by Th42;
hence thesis by Th23;
end;

theorem Th44: :: A107
for L being satisfying_DN_1 (non empty ComplLattStr),
x, y being Element of L holds
(x + y)` + x = x + y`
proof
let L be satisfying_DN_1 (non empty ComplLattStr);
let x, y be Element of L;
set Z = x;
x + (y + ((Z + y)` + x)`)` = (Z + y)` + x by Th38;
hence thesis by Th28;
end;

theorem Th45: :: A108
for L being satisfying_DN_1 (non empty ComplLattStr),
x, y being Element of L holds
(x + (x + y`)`)` = (x + y)`
proof
let L be satisfying_DN_1 (non empty ComplLattStr);
let x, y be Element of L;
(x + ((x + y)` + x)`)` = (x + y)` by Th8;
hence thesis by Th44;
end;

theorem Th46: :: A109
for L being satisfying_DN_1 (non empty ComplLattStr),
x, y, z being Element of L holds
((x + y)` + (x + z))` + y = y
proof
let L be satisfying_DN_1 (non empty ComplLattStr);
let x, y, z be Element of L;
((x + y)` + ((x + y)` + (x + z)`)`)` = ((x + y)` + (x + z))` by Th45;
hence thesis by Th40;
end;

theorem Th47: :: A110
for L being satisfying_DN_1 (non empty ComplLattStr),
x, y, z being Element of L holds
(((x + y)` + z)` + (x` + y)`)` + y = (x` + y)``
proof
let L be satisfying_DN_1 (non empty ComplLattStr);
let x, y, z be Element of L;
((((x + y)` + z)` + (x` + y)`)` + y)`` = (x` + y)`` by Th11;
hence thesis by Th23;
end;

theorem Th48: :: A111
for L being satisfying_DN_1 (non empty ComplLattStr),
x, y, z being Element of L holds
(((x + y)` + z)` + (x` + y)`)` + y = x` + y
proof
let L be satisfying_DN_1 (non empty ComplLattStr);
let x, y, z be Element of L;
(((x + y)` + z)` + (x` + y)`)` + y = (x` + y)`` by Th47;
hence thesis by Th23;
end;

theorem Th49: :: A112
for L being satisfying_DN_1 (non empty ComplLattStr),
x, y, z being Element of L holds
(x` + ((y + x)`` + (y + z))`)` + (y + z) = (y + x)``+ (y + z)
proof
let L be satisfying_DN_1 (non empty ComplLattStr);
let x, y, z be Element of L;
set X = (y + x)`, Y = (y + z), Z = x;
(((X + Y)` + Z)` + (X` + Y)`)` + Y = X` + Y by Th48;
hence thesis by Th46;
end;

theorem Th50: :: A113
for L being satisfying_DN_1 (non empty ComplLattStr),
x, y, z being Element of L holds
(x` + ((y + x) + (y + z))`)` + (y + z) = (y + x)`` + (y + z)
proof
let L be satisfying_DN_1 (non empty ComplLattStr);
let x, y, z be Element of L;
(x` + ((y + x)`` + (y + z))`)` + (y + z) = (y + x)`` + (y + z) by Th49;
hence thesis by Th23;
end;

theorem Th51: :: A114
for L being satisfying_DN_1 (non empty ComplLattStr),
x, y, z being Element of L holds
(x` + ((y + x) + (y + z))`)` + (y + z) = (y + x) + (y + z)
proof
let L be satisfying_DN_1 (non empty ComplLattStr);
let x, y, z be Element of L;
(x` + ((y + x) + (y + z))`)` + (y + z) = (y + x)`` + (y + z) by Th50;
hence thesis by Th23;
end;

theorem Th52: :: A115
for L being satisfying_DN_1 (non empty ComplLattStr),
x, y, z being Element of L holds
x`` + (y + z) = (y + x) + (y + z)
proof
let L be satisfying_DN_1 (non empty ComplLattStr);
let x, y, z be Element of L;
x` + ((y + x) + (y + z))` = x` by Th43;
hence thesis by Th51;
end;

theorem Th53: :: A117
for L being satisfying_DN_1 (non empty ComplLattStr),
x, y, z being Element of L holds
(x + y) + (x + z) = y + (x + z)
proof
let L be satisfying_DN_1 (non empty ComplLattStr);
let x, y, z be Element of L;
set Y = x, X = y;
X`` + (Y + z) = (Y + X) + (Y + z) by Th52;
hence thesis by Th23;
end;

theorem :: A118
for L being satisfying_DN_1 (non empty ComplLattStr),
x, y, z being Element of L holds
(x + y) + (x + z) = z + (x + y) by Th53;

theorem Th55: :: A119
for L being satisfying_DN_1 (non empty ComplLattStr),
x, y, z being Element of L holds
x + (y + z) = z + (y + x)
proof
let L be satisfying_DN_1 (non empty ComplLattStr);
let x, y, z be Element of L;
(y + x) + (y + z) = z + (y + x) by Th53;
hence thesis by Th53;
end;

theorem :: A120
for L being satisfying_DN_1 (non empty ComplLattStr),
x, y, z being Element of L holds
x + (y + z) = y + (z + x) by Th55;

theorem :: A121
for L being satisfying_DN_1 (non empty ComplLattStr),
x, y, z being Element of L holds
(x + y) + z = x + (y + z) by Th55;

Lm2:
for L being satisfying_DN_1 (non empty ComplLattStr) holds
L is join-associative
proof
let L;
for x, y, z holds (x + y) + z = x + (y + z) by Th55;
hence thesis by LATTICES:def 5;
end;

Lm3:  L is Robbins
proof
for x, y holds ((x + y)` + (x + y`)`)` = x by Th6;
hence L is Robbins by ROBBINS1:def 5;
end;

definition
cluster satisfying_DN_1 -> join-associative (non empty ComplLattStr);
coherence by Lm2;
cluster satisfying_DN_1 -> Robbins (non empty ComplLattStr);
coherence by Lm3;
end;

theorem Th58:
for L being non empty ComplLattStr,
x, z being Element of L st
L is join-commutative join-associative Huntington holds
(z + x) *' (z + x`) = z
proof
let L be non empty ComplLattStr;
let x, z be Element of L;
assume L is join-commutative join-associative Huntington;
then reconsider L' = L as join-commutative join-associative Huntington
(non empty ComplLattStr);
reconsider z' = z, x' = x as Element of L';
(z' + x') *' (z' + x'`) = z' + (x' *' x'`) by ROBBINS1:32
.= z' + Bot L' by ROBBINS1:16
.= z' by ROBBINS1:14;
hence thesis;
end;

theorem Th59:
for L being non empty ComplLattStr st
L is join-commutative join-associative Robbins holds
L is satisfying_DN_1
proof
let L be non empty ComplLattStr;
assume
A1: L is join-commutative join-associative Robbins; then
reconsider L' = L as join-commutative join-associative Robbins
(non empty ComplLattStr);
A2: L' is Huntington;
let x, y, z, u be Element of L;
A3: ((x + y)` + z) *' z = (z + (x + y)`) *' z by A1,LATTICES:def 4
.= z *' (z + (x + y)`) by A1,ROBBINS1:8
.= z by A2,ROBBINS1:22;
A4: (z + x) *' (z + x`) = z by A2,Th58;
A5: (((x + y)` + z) *' x) + z = z + (((x + y)` + z) *' x)
by A1,LATTICES:def 4
.= (z + ((x + y)` + z)) *' (z + x) by A2,ROBBINS1:32
.= (((x + y)` + z) + z) *' (z + x) by A2,LATTICES:def 4
.= ((x + y)` + (z + z)) *' (z + x) by A2,LATTICES:def 5
.= ((x + y)` + z) *' (z + x) by A2,ROBBINS1:13
.= ((x` *' y`)`` + z) *' (z + x) by A2,ROBBINS1:18
.= ((x` *' y`) + z) *' (z + x) by A2,ROBBINS1:3
.= (z + (x` *' y`)) *' (z + x) by A2,LATTICES:def 4
.= ((z + x`) *' (z + y`)) *' (z + x) by A2,ROBBINS1:32
.= (z + x) *' ((z + x`) *' (z + y`)) by A2,ROBBINS1:8
.= (z + x) *' ((x` + z) *' (z + y`)) by A2,LATTICES:def 4
.= (z + x) *' ((x` + z) *' (y` + z)) by A2,LATTICES:def 4
.= (z + x) *' (x` + z) *' (y` + z) by A2,ROBBINS1:17
.= (z + x) *' (z + x`) *' (y` + z) by A2,LATTICES:def 4
.= z *' (z + y`) by A2,A4,LATTICES:def 4
.= z by A2,ROBBINS1:22;
(((x + y)` + z)` + (x + (z` + (z + u)`)`)`)` =
(((x + y)` + z)`` *' (x + (z` + (z + u)`)`)``)``
by A2,ROBBINS1:18
.= ((x + y)` + z)`` *' (x + (z` + (z + u)`)`)`` by A2,ROBBINS1:3
.= ((x + y)` + z)`` *' (x + (z` + (z + u)`)`) by A2,ROBBINS1:3
.= ((x + y)` + z) *' (x + (z` + (z + u)`)`) by A2,ROBBINS1:3
.= ((x + y)`` *' z`)` *' (x + (z` + (z + u)`)`) by A2,ROBBINS1:18
.= ((x + y) *' z`)` *' (x + (z` + (z + u)`)`) by A2,ROBBINS1:3
.= ((x + y) *' z`)` *' (x + (z`` *' (z + u)``)``)
by A2,ROBBINS1:18
.= ((x + y) *' z`)` *' (x + (z *' (z + u)``)``)
by A2,ROBBINS1:3
.= ((x + y) *' z`)` *' (x + (z *' (z + u)``)) by A2,ROBBINS1:3
.= ((x + y) *' z`)` *' (x + (z *' (z + u))) by A2,ROBBINS1:3
.= ((x + y) *' z`)` *' (x + z) by A2,ROBBINS1:22
.= (((x + y) *' z`)` *' x) + (((x + y) *' z`)` *' z)
by A2,ROBBINS1:31
.= (((x + y)`` *' z`)` *' x) + (((x + y) *' z`)` *' z)
by A2,ROBBINS1:3
.= (((x + y)` + z) *' x) + (((x + y) *' z`)` *' z)
by A2,ROBBINS1:18
.= (((x + y)` + z) *' x) + (((x + y)`` *' z`)` *' z)
by A2,ROBBINS1:3
.= z by A2,A3,A5,ROBBINS1:18;
hence thesis;
end;

definition
cluster join-commutative join-associative Robbins -> satisfying_DN_1
(non empty ComplLattStr);
coherence by Th59;
end;

definition
cluster satisfying_DN_1 de_Morgan preOrthoLattice;
existence
proof
take TrivOrtLat;
thus thesis;
end;
end;

definition
cluster satisfying_DN_1 de_Morgan -> Boolean preOrthoLattice;
coherence
proof
let L be preOrthoLattice;
assume L is satisfying_DN_1 de_Morgan; then
reconsider L' = L as satisfying_DN_1 de_Morgan preOrthoLattice;
L' is Boolean;
hence thesis;
end;
cluster Boolean -> satisfying_DN_1 (well-complemented preOrthoLattice);
coherence
proof
let L be well-complemented preOrthoLattice;
assume
A1: L is Boolean;
reconsider L' = L as Boolean well-complemented preOrthoLattice by A1;
L' is satisfying_DN_1;
hence thesis;
end;
end;

begin :: Meredith Two Axioms for Boolean Algebras

definition let L be non empty ComplLattStr;
attr L is satisfying_MD_1 means :Def2:
for x, y being Element of L holds
(x` + y)` + x = x;
attr L is satisfying_MD_2 means :Def3:
for x, y, z being Element of L holds
(x` + y)` + (z + y) = y + (z + x);
end;

Lm4: now
let L be non empty ComplLattStr;
assume
A1:  L is satisfying_MD_1 satisfying_MD_2;
A2:  for x, y being Element of L holds
x` + (x` + y) = x` + y
proof
let x, y be Element of L;
set X = x` + y;
X` + x = x by A1,Def2;
hence thesis by A1,Def2;
end;

A3:  for x, y, z being Element of L holds
((x` + y)` + z)` + (x` + z) = z + (x` + y)
proof
let x, y, z be Element of L;
((x` + y)` + z)` + (x` + z) = z + (x` + (x` + y)) by A1,Def3
.= z + (x` + y) by A2;
hence thesis;
end;

A4: for x, y, z being Element of L holds
(x` + y)` + ((x` + z)` + y) = y + x
proof
let x, y, z be Element of L;
(x` + y)` + ((x` + z)` + y) = y + ((x` + z)` + x) by A1,Def3
.= y + x by A1,Def2;
hence thesis;
end;

A5: for x, y, z being Element of L holds
(x` + ((y + x)` + z)`)` + (y + ((y + x)` + z)`) = y + x
proof
let x, y, z be Element of L;
set P = ((y + x)` + z)`;
(x` + P)` + (y + P) = P + (y + x) by A1,Def3
.= y + x by A1,Def2;
hence thesis;
end;

A6: for x, y being Element of L holds
(x` + y)` + y = y + x
proof
let x, y be Element of L;
set X = x` + y;
A7:    X` + (X` + y) = y + (X` + x) by A1,Def3;
(x` + y)` + y = X` + (X` + y) by A2
.= y + x by A1,A7,Def2;
hence thesis;
end;

A8: for x, y being Element of L holds
x + (y + (y + x)) = y + x
proof
let x, y be Element of L;
set Z = y + x;
x + (y + (y + x)) = (Z` + x)` + (y + x) by A1,Def3
.= y + x by A1,Def2;
hence thesis;
end;

A9: for x, y being Element of L holds
x + (y` + x) = y` + x
proof
let x, y be Element of L;
x + (y` + x) = ((y` + x)` + x)` + (y` + x) by A3
.= y` + x by A1,Def2;
hence thesis;
end;

A10: for x being Element of L holds
x + x = x
proof
let x be Element of L;
x + x = (x` + x)` + x by A6
.= x by A1,Def2;
hence thesis;
end;

A11: for x, y being Element of L holds
x + (x + y) = x + y
proof
let x, y be Element of L;
x + (x + y) = (y` + x)` + (x + x) by A1,Def3
.= (y` + x)` + x by A10
.= x + y by A6;
hence thesis;
end;

A12: for x, y being Element of L holds
(x + y) + y = x + y
proof
let x, y be Element of L;
set Y = x + y;
(x + y) + y = (y` + (x + y))` + (x + y) by A6
.= (y` + (x + y))` + (x + (x + y)) by A11
.= Y + (x + y) by A1,Def3
.= x + y by A10;
hence thesis;
end;

A13:
for x being Element of L holds
x`` + x = x
proof
let x be Element of L;
(x` + x`)` + x = x by A1,Def2;
hence thesis by A10;
end;

A14:
for x, y being Element of L holds
x + (y + x) = y + x
proof
let x, y be Element of L;
x + (y + x) = x + (y + (y + x)) by A11
.= y + x by A8;
hence thesis;
end;

A15:
for x, y being Element of L holds
x + (x`` + y) = x + y
proof
let x, y be Element of L;
x + (x`` + y) = (y` + x)` + (x`` + x) by A1,Def3
.= (y` + x)` + x by A13
.= x + y by A6;
hence thesis;
end;

A16:
for x, y being Element of L holds
(x + y) + x = x + y
proof
let x, y be Element of L;
(x + y) + x = ((y` + x)` + x) + x by A6
.= (y` + x)` + x by A12
.= x + y by A6;
hence thesis;
end;

A17:
for x, y, z being Element of L holds
(x + y) + (y + z) = (x + y) + z
proof
let x, y, z be Element of L;
set Y = x + y;
(x + y) + z = (z` + Y)` + Y by A6
.= (z` + Y)` + (y + Y) by A14
.= Y + (y + z) by A1,Def3;
hence thesis;
end;

A18:
for x, y being Element of L holds
(x + y`)` + y = y
proof
let x, y be Element of L;
(x + y`)` + y = (y` + (x + y`))` + y by A14
.= y by A1,Def2;
hence thesis;
end;

A19:
for x being Element of L holds
x + x`` = x
proof
let x be Element of L;
x + x`` = (x`` + x) + x`` by A13
.= x`` + x by A16
.= x by A13;
hence thesis;
end;

A20:
for x, y being Element of L holds
x + (x` + y)` = x
proof
let x, y be Element of L;
x + (x` + y)` = ((x` + y)` + x) + (x` + y)` by A1,Def2
.= (x` + y)` + x by A16
.= x by A1,Def2;
hence thesis;
end;

A21:
for x, y being Element of L holds
x + (y + x`)` = x
proof
let x, y be Element of L;
x + (y + x`)` = ((y + x`)` + x) + (y + x`)` by A18
.= (y + x`)` + x by A16
.= x by A18;
hence thesis;
end;

A22:
for x, y being Element of L holds
(x` + (x + y)`)` + (y` + (x + y)`) = y` + x
proof
let x, y be Element of L;
(x` + (x + y)`)` + (y` + (x + y)`)
= (x` + (x + y)`)` + (y` + ((y` + x)` + x)`) by A6
.= (x` + ((y` + x)` + x)`)` + (y` + ((y` + x)` + x)`) by A6
.= y` + x by A5;
hence thesis;
end;

A23: for x, y being Element of L holds
(x + y)` + x = y` + x
proof
let x, y be Element of L;
set Y = y` + x;
y` + x = x + (y` + x) by A9
.= (Y` + x)` + x by A6
.= (x + y)` + x by A6;
hence thesis;
end;

A24:
for x, y being Element of L holds
(x + y)` + (y` + x)` = x` + (y` + x)`
proof
let x, y be Element of L;
(x + y)` + (y` + x)` = ((y` + x)` + x)` + (y` + x)` by A6
.= x` + (y` + x)` by A23;
hence thesis;
end;

A25:
for x being Element of L holds
x + x```` = x
proof
let x be Element of L;
x + x```` = x + (x`` + x````) by A15
.= x + x`` by A19
.= x by A19;
hence thesis;
end;

A26:
for x being Element of L holds
x``` = x`
proof
let x be Element of L;
x``` = (x + x````)` + x``` by A18
.= x` + x``` by A25
.= x` by A19;
hence thesis;
end;

A27:
for x, y being Element of L holds
x + y`` = x + y
proof
let x, y be Element of L;
x + y = (y` + x)` + ((y` + x)` + x) by A4
.= (y` + x)` + ((y``` + x)` + x) by A26
.= (y``` + x)` + ((y``` + x)` + x) by A26
.= x + y`` by A4;
hence thesis;
end;

A28:
for x being Element of L holds
x`` = x
proof
let x be Element of L;
x`` = (x``` + x``)` + x`` by A1,Def2
.= (x` + x``)` + x`` by A26
.= (x` + x``)` + x by A27
.= x by A1,Def2;
hence thesis;
end;

A29:
for x, y being Element of L holds
x` + (y + x)` = x`
proof
let x, y be Element of L;
x` = x` + (y + x``)` by A21
.= x` + (y + x)` by A28;
hence thesis;
end;

A30:
for x, y being Element of L holds
x` + (x + y)` = x`
proof
let x, y be Element of L;
x` = x` + (x`` + y)` by A20
.= x` + (x + y)` by A28;
hence thesis;
end;

A31:
for x, y being Element of L holds
x + y` = y` + x
proof
let x, y be Element of L;
y` + x = (x` + (x + y)`)` + (y` + (x + y)`) by A22
.= x`` + (y` + (x + y)`) by A30
.= x`` + y` by A29
.= x + y` by A28;
hence thesis;
end;

A32:
for x, y being Element of L holds
x + y = y + x
proof
let x, y be Element of L;
y`` = y by A28;
hence thesis by A31;
end;
hence L is join-commutative by LATTICES:def 4;

for x, y being Element of L holds
(x` + y`)` + (x` + y)` = x
proof
let x, y be Element of L;
(x` + y`)` + (x` + y)` = (y` + x`)` + (x` + y)` by A32
.= (x` + y)` + (y` + x`)` by A32
.= x`` + (y` + x`)` by A24
.= x + (y` + x`)` by A28
.= x by A21;
hence thesis;
end;
hence L is Huntington by ROBBINS1:def 6;

for x, y, z being Element of L holds
(x + y) + z = x + (y + z)
proof
let x, y, z be Element of L;
A33: for x, y, z being Element of L holds
(x + y) + (z + x) = y + (x + z)
proof
let x, y, z be Element of L;
(x + y) + (z + x) = (z + x) + (x + y) by A32
.= (z + x) + y by A17
.= (x + z) + y by A32
.= y + (x + z) by A32;
hence thesis;
end;
(y + x) + (z + y) = x + (y + z) by A33; then
A34:    (x + y) + (z + y) = x + (y + z) by A32;
(x + y) + z = (x + y) + (y + z) by A17
.= x + (y + z) by A32,A34;
hence thesis;
end;
hence L is join-associative by LATTICES:def 5;
end;

definition
cluster satisfying_MD_1 satisfying_MD_2 ->
join-commutative join-associative Huntington (non empty ComplLattStr);
coherence by Lm4;
cluster join-commutative join-associative Huntington ->
satisfying_MD_1 satisfying_MD_2 (non empty ComplLattStr);
coherence
proof
let L be non empty ComplLattStr;
assume L is join-commutative join-associative Huntington; then
reconsider L' = L as join-commutative join-associative Huntington
(non empty ComplLattStr);
A1: L' is satisfying_MD_1
proof
let x, y be Element of L';
(x` + y)` + x = (x` + y``)` + x by ROBBINS1:3
.= (x *' y`) + x by ROBBINS1:def 4
.= x by ROBBINS1:21;
hence thesis;
end;
L' is satisfying_MD_2
proof
let x, y, z be Element of L';
set Z = z + y;
consider k being Element of L' such that
A2:   k + k` = Top L' by ROBBINS1:def 8;
A3:   Z + y` = z + (y + y`) by LATTICES:def 5
.= z + Top L' by A2,ROBBINS1:4
.= Top L' by ROBBINS1:20;
(x` + y)` + (z + y) = (x` + y``)` + (z + y) by ROBBINS1:3
.= (x *' y`) + (z + y) by ROBBINS1:def 4
.= (Z + x) *' (Z + y`) by ROBBINS1:32
.= Z + x by A3,ROBBINS1:15
.= y + (z + x) by LATTICES:def 5;
hence thesis;
end;
hence thesis by A1;
end;
end;

definition
cluster satisfying_MD_1 satisfying_MD_2 satisfying_DN_1 de_Morgan
preOrthoLattice;
existence
proof
take TrivOrtLat;
thus thesis;
end;
end;

definition
cluster satisfying_MD_1 satisfying_MD_2 de_Morgan ->
Boolean preOrthoLattice;
coherence
proof
let L be preOrthoLattice;
assume L is satisfying_MD_1 satisfying_MD_2 de_Morgan; then
reconsider L' = L as satisfying_MD_1 satisfying_MD_2 de_Morgan
preOrthoLattice;
L' is Boolean;
hence thesis;
end;
cluster Boolean -> satisfying_MD_1 satisfying_MD_2 (well-complemented
preOrthoLattice);
coherence
proof
let L be well-complemented preOrthoLattice;
assume
A1: L is Boolean;
reconsider L' = L as Boolean well-complemented preOrthoLattice by A1;
L' is satisfying_MD_1 satisfying_MD_2;
hence thesis;
end;
end;
```