let S be full SubRelStr of L; :: thesis: ( S is bottom-inheriting & S is join-inheriting implies S is finite-sups-inheriting )
assume
( S is bottom-inheriting & S is join-inheriting )
; :: thesis: S is finite-sups-inheriting
then reconsider S' = S as full join-inheriting bottom-inheriting SubRelStr of L ;
let X be finite Subset of S; :: according to WAYBEL34:def 18 :: thesis: ( ex_sup_of X,L implies "\/" X,L in the carrier of S )
reconsider X' = X as Subset of S' ;
A1:
X is finite
;
defpred S1[ set ] means for Y being finite Subset of S' st Y = L holds
( ex_sup_of Y,L & "\/" Y,L = sup Y );
( Bottom L = "\/" {} ,L & Bottom S' = "\/" {} ,S' & ex_sup_of {} ,L )
by YELLOW_0:42;
then A2:
S1[ {} ]
by Th64;
A3:
for x, B being set st x in X & B c= X & S1[B] holds
S1[B \/ {x}]
proof
let x,
B be
set ;
:: thesis: ( x in X & B c= X & S1[B] implies S1[B \/ {x}] )
assume that
(
x in X &
B c= X )
and A4:
for
Y being
finite Subset of
S' st
Y = B holds
(
ex_sup_of Y,
L &
"\/" Y,
L = sup Y )
;
:: thesis: S1[B \/ {x}]
let Y be
finite Subset of
S';
:: thesis: ( Y = B \/ {x} implies ( ex_sup_of Y,L & "\/" Y,L = sup Y ) )
assume A5:
Y = B \/ {x}
;
:: thesis: ( ex_sup_of Y,L & "\/" Y,L = sup Y )
A6:
(
B c= Y &
{x} c= Y )
by A5, XBOOLE_1:7;
then reconsider Z =
B as
finite Subset of
S' by XBOOLE_1:1;
A7:
(
ex_sup_of Z,
L &
"\/" Z,
L = sup Z )
by A4;
x in Y
by A6, ZFMISC_1:37;
then reconsider x =
x as
Element of
S' ;
reconsider a =
x as
Element of
L by YELLOW_0:59;
A8:
ex_sup_of {a},
L
by YELLOW_0:38;
hence
ex_sup_of Y,
L
by A5, A7, YELLOW_2:3;
:: thesis: "\/" Y,L = sup Y
(
Z = {} or (
Z <> {} &
S' is
with_suprema ) )
;
then A9:
(
ex_sup_of {x},
S' &
ex_sup_of Z,
S' )
by YELLOW_0:42, YELLOW_0:54;
thus "\/" Y,
L =
("\/" Z,L) "\/" (sup {a})
by A5, A7, A8, YELLOW_2:3
.=
("\/" Z,L) "\/" a
by YELLOW_0:39
.=
(sup Z) "\/" x
by A7, YELLOW_0:71
.=
(sup Z) "\/" (sup {x})
by YELLOW_0:39
.=
sup Y
by A5, A9, YELLOW_2:3
;
:: thesis: verum
end;
S1[X]
from FINSET_1:sch 2(A1, A2, A3);
then
( "\/" X,L = sup X' & sup X' in the carrier of S' )
;
hence
( ex_sup_of X,L implies "\/" X,L in the carrier of S )
; :: thesis: verum