let T be TopSpace; :: thesis: LattStr(# (Domains_of T),(D-Union T),(D-Meet T) #) is C_Lattice
set L = LattStr(# (Domains_of T),(D-Union T),(D-Meet T) #);
A1: LattStr(# (Domains_of T),(D-Union T),(D-Meet T) #) is join-commutative

proof

let a, b be Element of LattStr(# (Domains_of T),(D-Union T),(D-Meet T) #); :: according to LATTICES:def 4 :: thesis: a "\/" b = b "\/" a
reconsider A = a, B = b as Element of Domains_of T ;
thus a "\/" b = (Int (Cl (B \/ A))) \/ (B \/ A) by Def2
.= b "\/" a by Def2 ; :: thesis: verum

end;

A2: LattStr(# (Domains_of T),(D-Union T),(D-Meet T) #) is meet-absorbing

proof

let a, b be Element of LattStr(# (Domains_of T),(D-Union T),(D-Meet T) #); :: according to LATTICES:def 8 :: thesis: (a "/\" b) "\/" b = b
reconsider A = a, B = b as Element of Domains_of T ;
A3: (Cl (Int (A /\ B))) /\ (A /\ B) c= A /\ B by XBOOLE_1:17;
B in { D where D is Subset of T : D is condensed } ;
then ex D being Subset of T st
( D = B & D is condensed ) ;
then A4: Int (Cl B) c= B by TOPS_1:def 6;
A5: A /\ B c= B by XBOOLE_1:17;
a "/\" b = (Cl (Int (A /\ B))) /\ (A /\ B) by Def3;
hence (a "/\" b) "\/" b = (Int (Cl (((Cl (Int (A /\ B))) /\ (A /\ B)) \/ B))) \/ (((Cl (Int (A /\ B))) /\ (A /\ B)) \/ B) by Def2
.= (Int (Cl (((Cl (Int (A /\ B))) /\ (A /\ B)) \/ B))) \/ B by A3, A5, XBOOLE_1:1, XBOOLE_1:12
.= (Int (Cl B)) \/ B by A3, A5, XBOOLE_1:1, XBOOLE_1:12
.= b by A4, XBOOLE_1:12 ;
:: thesis: verum

end;

A6: LattStr(# (Domains_of T),(D-Union T),(D-Meet T) #) is join-associative

proof

let a, b, c be Element of LattStr(# (Domains_of T),(D-Union T),(D-Meet T) #); :: according to LATTICES:def 5 :: thesis: a "\/" (b "\/" c) = (a "\/" b) "\/" c
reconsider A = a, B = b, C = c as Element of Domains_of T ;
A7: a "\/" b = (Int (Cl (A \/ B))) \/ (A \/ B) by Def2;
b "\/" c = (Int (Cl (B \/ C))) \/ (B \/ C) by Def2;
hence a "\/" (b "\/" c) = (Int (Cl (A \/ ((Int (Cl (B \/ C))) \/ (B \/ C))))) \/ (A \/ ((Int (Cl (B \/ C))) \/ (B \/ C))) by Def2
.= (Int (Cl (A \/ (B \/ C)))) \/ (A \/ (B \/ C)) by Th10
.= (Int (Cl (A \/ (B \/ C)))) \/ ((A \/ B) \/ C) by XBOOLE_1:4
.= (Int (Cl ((A \/ B) \/ C))) \/ ((A \/ B) \/ C) by XBOOLE_1:4
.= (Int (Cl (((Int (Cl (A \/ B))) \/ (A \/ B)) \/ C))) \/ (((Int (Cl (A \/ B))) \/ (A \/ B)) \/ C) by Th10
.= (a "\/" b) "\/" c by A7, Def2 ;
:: thesis: verum

end;

A8: LattStr(# (Domains_of T),(D-Union T),(D-Meet T) #) is meet-commutative

proof

let a, b be Element of LattStr(# (Domains_of T),(D-Union T),(D-Meet T) #); :: according to LATTICES:def 6 :: thesis: a "/\" b = b "/\" a
reconsider A = a, B = b as Element of Domains_of T ;
thus a "/\" b = (Cl (Int (B /\ A))) /\ (B /\ A) by Def3
.= b "/\" a by Def3 ; :: thesis: verum

end;

A9: LattStr(# (Domains_of T),(D-Union T),(D-Meet T) #) is join-absorbing

proof

let a, b be Element of LattStr(# (Domains_of T),(D-Union T),(D-Meet T) #); :: according to LATTICES:def 9 :: thesis: a "/\" (a "\/" b) = a
reconsider A = a, B = b as Element of Domains_of T ;
A10: A c= A \/ B by XBOOLE_1:7;
A in { D where D is Subset of T : D is condensed } ;
then ex D being Subset of T st
( D = A & D is condensed ) ;
then A11: A c= Cl (Int A) by TOPS_1:def 6;
A12: A \/ B c= (Int (Cl (A \/ B))) \/ (A \/ B) by XBOOLE_1:7;
a "\/" b = (Int (Cl (A \/ B))) \/ (A \/ B) by Def2;
hence a "/\" (a "\/" b) = (Cl (Int (A /\ ((Int (Cl (A \/ B))) \/ (A \/ B))))) /\ (A /\ ((Int (Cl (A \/ B))) \/ (A \/ B))) by Def3
.= (Cl (Int (A /\ ((Int (Cl (A \/ B))) \/ (A \/ B))))) /\ A by A10, A12, XBOOLE_1:1, XBOOLE_1:28
.= (Cl (Int A)) /\ A by A10, A12, XBOOLE_1:1, XBOOLE_1:28
.= a by A11, XBOOLE_1:28 ;
:: thesis: verum

end;

LattStr(# (Domains_of T),(D-Union T),(D-Meet T) #) is meet-associative

proof

let a, b, c be Element of LattStr(# (Domains_of T),(D-Union T),(D-Meet T) #); :: according to LATTICES:def 7 :: thesis: a "/\" (b "/\" c) = (a "/\" b) "/\" c
reconsider A = a, B = b, C = c as Element of Domains_of T ;
A13: a "/\" b = (Cl (Int (A /\ B))) /\ (A /\ B) by Def3;
b "/\" c = (Cl (Int (B /\ C))) /\ (B /\ C) by Def3;
hence a "/\" (b "/\" c) = (Cl (Int (A /\ ((Cl (Int (B /\ C))) /\ (B /\ C))))) /\ (A /\ ((Cl (Int (B /\ C))) /\ (B /\ C))) by Def3
.= (Cl (Int (A /\ (B /\ C)))) /\ (A /\ (B /\ C)) by Th12
.= (Cl (Int (A /\ (B /\ C)))) /\ ((A /\ B) /\ C) by XBOOLE_1:16
.= (Cl (Int ((A /\ B) /\ C))) /\ ((A /\ B) /\ C) by XBOOLE_1:16
.= (Cl (Int (((Cl (Int (A /\ B))) /\ (A /\ B)) /\ C))) /\ (((Cl (Int (A /\ B))) /\ (A /\ B)) /\ C) by Th12
.= (a "/\" b) "/\" c by A13, Def3 ;
:: thesis: verum

end;

then reconsider L = LattStr(# (Domains_of T),(D-Union T),(D-Meet T) #) as Lattice by A1, A6, A2, A8, A9;
A14: L is lower-bounded

proof

{} T is condensed by Th14;
then {} T in { D where D is Subset of T : D is condensed } ;
then reconsider c = {} T as Element of L ;
take c ; :: according to LATTICES:def 13 :: thesis: for b₁ being Element of the carrier of L holds
( c "/\" b₁ = c & b₁ "/\" c = c )
let a be Element of L; :: thesis: ( c "/\" a = c & a "/\" c = c )
reconsider C = c, A = a as Element of Domains_of T ;
C /\ A = C ;
hence c "/\" a = (Cl (Int C)) /\ C by Def3
.= c ;
:: thesis: a "/\" c = c
hence a "/\" c = c ; :: thesis: verum

end;

L is upper-bounded

proof

[#] T is condensed by Th15;
then [#] T in { D where D is Subset of T : D is condensed } ;
then reconsider c = [#] T as Element of L ;
take c ; :: according to LATTICES:def 14 :: thesis: for b₁ being Element of the carrier of L holds
( c "\/" b₁ = c & b₁ "\/" c = c )
let a be Element of L; :: thesis: ( c "\/" a = c & a "\/" c = c )
reconsider C = c, A = a as Element of Domains_of T ;
C \/ A = C by XBOOLE_1:12;
hence c "\/" a = (Int (Cl C)) \/ C by Def2
.= c by XBOOLE_1:12 ;
:: thesis: a "\/" c = c
hence a "\/" c = c ; :: thesis: verum

end;

then reconsider L = L as 01_Lattice by A14;
L is complemented

proof

[#] T is condensed by Th15;
then [#] T in { D where D is Subset of T : D is condensed } ;
then reconsider c = [#] T as Element of L ;
let b be Element of L; :: according to LATTICES:def 19 :: thesis: ex b₁ being Element of the carrier of L st b₁ is_a_complement_of b
reconsider B = b as Element of Domains_of T ;
A15: B ` misses B by XBOOLE_1:79;
B in { D where D is Subset of T : D is condensed } ;
then ex D being Subset of T st
( D = B & D is condensed ) ;
then B ` is condensed by Th16;
then B ` in { D where D is Subset of T : D is condensed } ;
then reconsider a = B ` as Element of L ;
take a ; :: thesis: a is_a_complement_of b
A16: for v being Element of L holds the L_meet of L . (c,v) = v

proof

let v be Element of L; :: thesis: the L_meet of L . (c,v) = v
reconsider V = v as Element of Domains_of T ;
V in { D where D is Subset of T : D is condensed } ;
then ex D being Subset of T st
( D = V & D is condensed ) ;
then A17: V c= Cl (Int V) by TOPS_1:def 6;
thus the L_meet of L . (c,v) = (Cl (Int (([#] T) /\ V))) /\ (([#] T) /\ V) by Def3
.= (Cl (Int (([#] T) /\ V))) /\ V by XBOOLE_1:28
.= (Cl (Int V)) /\ V by XBOOLE_1:28
.= v by A17, XBOOLE_1:28 ; :: thesis: verum

end;

thus a "\/" b = (Int (Cl ((B `) \/ B))) \/ ((B `) \/ B) by Def2
.= (Int (Cl ((B `) \/ B))) \/ ([#] T) by PRE_TOPC:2
.= c by XBOOLE_1:12
.= Top L by A16, LATTICE2:17 ; :: according to LATTICES:def 18 :: thesis: ( b "\/" a = Top L & a "/\" b = Bottom L & b "/\" a = Bottom L )
hence b "\/" a = Top L ; :: thesis: ( a "/\" b = Bottom L & b "/\" a = Bottom L )
{} T is condensed by Th14;
then {} T in { D where D is Subset of T : D is condensed } ;
then reconsider c = {} T as Element of L ;
A18: for v being Element of L holds the L_join of L . (c,v) = v

proof

let v be Element of L; :: thesis: the L_join of L . (c,v) = v
reconsider V = v as Element of Domains_of T ;
V in { D where D is Subset of T : D is condensed } ;
then ex D being Subset of T st
( D = V & D is condensed ) ;
then A19: Int (Cl V) c= V by TOPS_1:def 6;
thus the L_join of L . (c,v) = (Int (Cl (({} T) \/ V))) \/ (({} T) \/ V) by Def2
.= (Int (Cl ((([#] T) `) \/ V))) \/ (({} T) \/ V) by XBOOLE_1:37
.= (Int (Cl ((([#] T) `) \/ ((V `) `)))) \/ ((([#] T) `) \/ V) by XBOOLE_1:37
.= (Int (Cl ((([#] T) /\ (V `)) `))) \/ ((([#] T) `) \/ ((V `) `)) by XBOOLE_1:54
.= (Int (Cl ((([#] T) /\ (V `)) `))) \/ ((([#] T) /\ (V `)) `) by XBOOLE_1:54
.= (Int (Cl ((V `) `))) \/ ((([#] T) /\ (V `)) `) by XBOOLE_1:28
.= (Int (Cl V)) \/ ((V `) `) by XBOOLE_1:28
.= v by A19, XBOOLE_1:12 ; :: thesis: verum

end;

thus a "/\" b = (Cl (Int ((B `) /\ B))) /\ ((B `) /\ B) by Def3
.= (Cl (Int ((B `) /\ B))) /\ ({} T) by A15
.= Bottom L by A18, LATTICE2:15 ; :: thesis: b "/\" a = Bottom L
hence b "/\" a = Bottom L ; :: thesis: verum

end;

hence LattStr(# (Domains_of T),(D-Union T),(D-Meet T) #) is C_Lattice ; :: thesis: verum