:: TEX_3 semantic presentation

begin

theorem :: TEX_3:1
for X being ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace)
for A, B being ( ( ) ( ) Subset of ) st A : ( ( ) ( ) Subset of ) ,B : ( ( ) ( ) Subset of ) constitute_a_decomposition holds
( not A : ( ( ) ( ) Subset of ) is empty iff B : ( ( ) ( ) Subset of ) is proper ) ;

theorem :: TEX_3:2
for X being ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace)
for A, B being ( ( ) ( ) Subset of ) st A : ( ( ) ( ) Subset of ) ,B : ( ( ) ( ) Subset of ) constitute_a_decomposition holds
( A : ( ( ) ( ) Subset of ) is dense iff B : ( ( ) ( ) Subset of ) is boundary ) ;

theorem :: TEX_3:3
for X being ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace)
for A, B being ( ( ) ( ) Subset of ) st A : ( ( ) ( ) Subset of ) ,B : ( ( ) ( ) Subset of ) constitute_a_decomposition holds
( A : ( ( ) ( ) Subset of ) is boundary iff B : ( ( ) ( ) Subset of ) is dense ) ;

theorem :: TEX_3:4
for X being ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace)
for A, B being ( ( ) ( ) Subset of ) st A : ( ( ) ( ) Subset of ) ,B : ( ( ) ( ) Subset of ) constitute_a_decomposition holds
( A : ( ( ) ( ) Subset of ) is everywhere_dense iff B : ( ( ) ( ) Subset of ) is nowhere_dense ) ;

theorem :: TEX_3:5
for X being ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace)
for A, B being ( ( ) ( ) Subset of ) st A : ( ( ) ( ) Subset of ) ,B : ( ( ) ( ) Subset of ) constitute_a_decomposition holds
( A : ( ( ) ( ) Subset of ) is nowhere_dense iff B : ( ( ) ( ) Subset of ) is everywhere_dense ) ;

theorem :: TEX_3:6
for X being ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace)
for Y1, Y2 being ( ( non empty ) ( non empty TopSpace-like ) SubSpace of X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) st Y1 : ( ( non empty ) ( non empty TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) ,Y2 : ( ( non empty ) ( non empty TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) constitute_a_decomposition holds
( Y1 : ( ( non empty ) ( non empty TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) is proper & Y2 : ( ( non empty ) ( non empty TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) is proper ) ;

theorem :: TEX_3:7
for X being ( ( non trivial TopSpace-like ) ( non empty non trivial TopSpace-like ) TopSpace)
for D being ( ( non empty proper ) ( non empty proper ) Subset of ) ex Y0 being ( ( non empty strict proper ) ( non empty strict TopSpace-like proper ) SubSpace of X : ( ( non trivial TopSpace-like ) ( non empty non trivial TopSpace-like ) TopSpace) ) st D : ( ( non empty proper ) ( non empty proper ) Subset of ) = the carrier of Y0 : ( ( non empty strict proper ) ( non empty strict TopSpace-like proper ) SubSpace of b1 : ( ( non trivial TopSpace-like ) ( non empty non trivial TopSpace-like ) TopSpace) ) : ( ( ) ( non empty ) set ) ;

theorem :: TEX_3:8
for X being ( ( non trivial TopSpace-like ) ( non empty non trivial TopSpace-like ) TopSpace)
for Y1 being ( ( non empty proper ) ( non empty TopSpace-like proper ) SubSpace of X : ( ( non trivial TopSpace-like ) ( non empty non trivial TopSpace-like ) TopSpace) ) ex Y2 being ( ( non empty strict proper ) ( non empty strict TopSpace-like proper ) SubSpace of X : ( ( non trivial TopSpace-like ) ( non empty non trivial TopSpace-like ) TopSpace) ) st Y1 : ( ( non empty proper ) ( non empty TopSpace-like proper ) SubSpace of b1 : ( ( non trivial TopSpace-like ) ( non empty non trivial TopSpace-like ) TopSpace) ) ,Y2 : ( ( non empty strict proper ) ( non empty strict TopSpace-like proper ) SubSpace of b1 : ( ( non trivial TopSpace-like ) ( non empty non trivial TopSpace-like ) TopSpace) ) constitute_a_decomposition ;

begin

definition
let X be ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ;
let IT be ( ( ) ( TopSpace-like ) SubSpace of X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) ;
attr IT is dense means :: TEX_3:def 1
for A being ( ( ) ( ) Subset of ) st A : ( ( ) ( ) Subset of ) = the carrier of IT : ( ( ) ( ) Element of K10(K10(X : ( ( ) ( ) TopStruct ) ) : ( ( ) ( ) set ) ) : ( ( ) ( ) set ) ) : ( ( ) ( ) set ) holds
A : ( ( ) ( ) Subset of ) is dense ;
end;

theorem :: TEX_3:9
for X being ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace)
for X0 being ( ( ) ( TopSpace-like ) SubSpace of X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) )
for A being ( ( ) ( ) Subset of ) st A : ( ( ) ( ) Subset of ) = the carrier of X0 : ( ( ) ( TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) : ( ( ) ( ) set ) holds
( X0 : ( ( ) ( TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) is dense iff A : ( ( ) ( ) Subset of ) is dense ) ;

registration
let X be ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ;
cluster closed dense -> non proper for ( ( ) ( ) SubSpace of X : ( ( ) ( ) TopStruct ) ) ;
cluster proper dense -> non closed for ( ( ) ( ) SubSpace of X : ( ( ) ( ) TopStruct ) ) ;
cluster closed proper -> non dense for ( ( ) ( ) SubSpace of X : ( ( ) ( ) TopStruct ) ) ;
end;

registration
let X be ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ;
cluster non empty strict TopSpace-like dense for ( ( ) ( ) SubSpace of X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopStruct ) ) ;
end;

theorem :: TEX_3:10
for X being ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace)
for A0 being ( ( non empty ) ( non empty ) Subset of ) st A0 : ( ( non empty ) ( non empty ) Subset of ) is dense holds
ex X0 being ( ( non empty strict dense ) ( non empty strict TopSpace-like dense ) SubSpace of X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) st A0 : ( ( non empty ) ( non empty ) Subset of ) = the carrier of X0 : ( ( non empty strict dense ) ( non empty strict TopSpace-like dense ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) : ( ( ) ( non empty ) set ) ;

theorem :: TEX_3:11
for X being ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace)
for X0 being ( ( non empty dense ) ( non empty TopSpace-like dense ) SubSpace of X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) )
for A being ( ( ) ( ) Subset of )
for B being ( ( ) ( ) Subset of ) st A : ( ( ) ( ) Subset of ) = B : ( ( ) ( ) Subset of ) holds
( B : ( ( ) ( ) Subset of ) is dense iff A : ( ( ) ( ) Subset of ) is dense ) ;

theorem :: TEX_3:12
for X being ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace)
for X1 being ( ( dense ) ( TopSpace-like dense ) SubSpace of X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) )
for X2 being ( ( ) ( TopSpace-like ) SubSpace of X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) st X1 : ( ( dense ) ( TopSpace-like dense ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) is ( ( ) ( TopSpace-like ) SubSpace of X2 : ( ( ) ( TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) ) holds
X2 : ( ( ) ( TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) is dense ;

theorem :: TEX_3:13
for X being ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace)
for X1 being ( ( non empty dense ) ( non empty TopSpace-like dense ) SubSpace of X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) )
for X2 being ( ( non empty ) ( non empty TopSpace-like ) SubSpace of X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) st X1 : ( ( non empty dense ) ( non empty TopSpace-like dense ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) is ( ( ) ( TopSpace-like ) SubSpace of X2 : ( ( non empty ) ( non empty TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) ) holds
X1 : ( ( non empty dense ) ( non empty TopSpace-like dense ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) is ( ( dense ) ( TopSpace-like dense ) SubSpace of X2 : ( ( non empty ) ( non empty TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) ) ;

theorem :: TEX_3:14
for X being ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace)
for X1 being ( ( non empty dense ) ( non empty TopSpace-like dense ) SubSpace of X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) )
for X2 being ( ( non empty dense ) ( non empty TopSpace-like dense ) SubSpace of X1 : ( ( non empty dense ) ( non empty TopSpace-like dense ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) ) holds X2 : ( ( non empty dense ) ( non empty TopSpace-like dense ) SubSpace of b2 : ( ( non empty dense ) ( non empty TopSpace-like dense ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) ) is ( ( non empty dense ) ( non empty TopSpace-like dense ) SubSpace of X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) ;

theorem :: TEX_3:15
for X, Y1, Y2 being ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) st Y2 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) = TopStruct(# the carrier of Y1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) : ( ( ) ( non empty ) set ) , the topology of Y1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) : ( ( ) ( non empty ) Element of K10(K10( the carrier of b2 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) : ( ( ) ( non empty ) set ) ) : ( ( ) ( ) set ) ) : ( ( ) ( ) set ) ) #) : ( ( strict ) ( non empty strict TopSpace-like ) TopStruct ) holds
( Y1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) is ( ( dense ) ( TopSpace-like dense ) SubSpace of X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) iff Y2 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) is ( ( dense ) ( TopSpace-like dense ) SubSpace of X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) ) ;

definition
let X be ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ;
let IT be ( ( ) ( TopSpace-like ) SubSpace of X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) ;
attr IT is everywhere_dense means :: TEX_3:def 2
for A being ( ( ) ( ) Subset of ) st A : ( ( ) ( ) Subset of ) = the carrier of IT : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopStruct ) : ( ( ) ( non empty ) set ) holds
A : ( ( ) ( ) Subset of ) is everywhere_dense ;
end;

theorem :: TEX_3:16
for X being ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace)
for X0 being ( ( ) ( TopSpace-like ) SubSpace of X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) )
for A being ( ( ) ( ) Subset of ) st A : ( ( ) ( ) Subset of ) = the carrier of X0 : ( ( ) ( TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) : ( ( ) ( ) set ) holds
( X0 : ( ( ) ( TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) is everywhere_dense iff A : ( ( ) ( ) Subset of ) is everywhere_dense ) ;

registration
let X be ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ;
cluster everywhere_dense -> dense for ( ( ) ( ) SubSpace of X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopStruct ) ) ;
cluster non dense -> non everywhere_dense for ( ( ) ( ) SubSpace of X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopStruct ) ) ;
cluster non proper -> everywhere_dense for ( ( ) ( ) SubSpace of X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopStruct ) ) ;
cluster non everywhere_dense -> proper for ( ( ) ( ) SubSpace of X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopStruct ) ) ;
end;

registration
let X be ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ;
cluster non empty strict TopSpace-like everywhere_dense for ( ( ) ( ) SubSpace of X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopStruct ) ) ;
end;

theorem :: TEX_3:17
for X being ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace)
for A0 being ( ( non empty ) ( non empty ) Subset of ) st A0 : ( ( non empty ) ( non empty ) Subset of ) is everywhere_dense holds
ex X0 being ( ( non empty strict everywhere_dense ) ( non empty strict TopSpace-like dense everywhere_dense ) SubSpace of X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) st A0 : ( ( non empty ) ( non empty ) Subset of ) = the carrier of X0 : ( ( non empty strict everywhere_dense ) ( non empty strict TopSpace-like dense everywhere_dense ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) : ( ( ) ( non empty ) set ) ;

theorem :: TEX_3:18
for X being ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace)
for X0 being ( ( non empty everywhere_dense ) ( non empty TopSpace-like dense everywhere_dense ) SubSpace of X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) )
for A being ( ( ) ( ) Subset of )
for B being ( ( ) ( ) Subset of ) st A : ( ( ) ( ) Subset of ) = B : ( ( ) ( ) Subset of ) holds
( B : ( ( ) ( ) Subset of ) is everywhere_dense iff A : ( ( ) ( ) Subset of ) is everywhere_dense ) ;

theorem :: TEX_3:19
for X being ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace)
for X1 being ( ( everywhere_dense ) ( TopSpace-like dense everywhere_dense ) SubSpace of X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) )
for X2 being ( ( ) ( TopSpace-like ) SubSpace of X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) st X1 : ( ( everywhere_dense ) ( TopSpace-like dense everywhere_dense ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) is ( ( ) ( TopSpace-like ) SubSpace of X2 : ( ( ) ( TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) ) holds
X2 : ( ( ) ( TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) is everywhere_dense ;

theorem :: TEX_3:20
for X being ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace)
for X1 being ( ( non empty everywhere_dense ) ( non empty TopSpace-like dense everywhere_dense ) SubSpace of X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) )
for X2 being ( ( non empty ) ( non empty TopSpace-like ) SubSpace of X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) st X1 : ( ( non empty everywhere_dense ) ( non empty TopSpace-like dense everywhere_dense ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) is ( ( ) ( TopSpace-like ) SubSpace of X2 : ( ( non empty ) ( non empty TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) ) holds
X1 : ( ( non empty everywhere_dense ) ( non empty TopSpace-like dense everywhere_dense ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) is ( ( everywhere_dense ) ( TopSpace-like dense everywhere_dense ) SubSpace of X2 : ( ( non empty ) ( non empty TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) ) ;

theorem :: TEX_3:21
for X being ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace)
for X1 being ( ( non empty everywhere_dense ) ( non empty TopSpace-like dense everywhere_dense ) SubSpace of X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) )
for X2 being ( ( non empty everywhere_dense ) ( non empty TopSpace-like dense everywhere_dense ) SubSpace of X1 : ( ( non empty everywhere_dense ) ( non empty TopSpace-like dense everywhere_dense ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) ) holds X2 : ( ( non empty everywhere_dense ) ( non empty TopSpace-like dense everywhere_dense ) SubSpace of b2 : ( ( non empty everywhere_dense ) ( non empty TopSpace-like dense everywhere_dense ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) ) is ( ( everywhere_dense ) ( TopSpace-like dense everywhere_dense ) SubSpace of X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) ;

theorem :: TEX_3:22
for X, Y1, Y2 being ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) st Y2 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) = TopStruct(# the carrier of Y1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) : ( ( ) ( non empty ) set ) , the topology of Y1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) : ( ( ) ( non empty ) Element of K10(K10( the carrier of b2 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) : ( ( ) ( non empty ) set ) ) : ( ( ) ( ) set ) ) : ( ( ) ( ) set ) ) #) : ( ( strict ) ( non empty strict TopSpace-like ) TopStruct ) holds
( Y1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) is ( ( everywhere_dense ) ( TopSpace-like dense everywhere_dense ) SubSpace of X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) iff Y2 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) is ( ( everywhere_dense ) ( TopSpace-like dense everywhere_dense ) SubSpace of X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) ) ;

registration
let X be ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ;
cluster open dense -> everywhere_dense for ( ( ) ( ) SubSpace of X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopStruct ) ) ;
cluster dense non everywhere_dense -> non open for ( ( ) ( ) SubSpace of X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopStruct ) ) ;
cluster open non everywhere_dense -> non dense for ( ( ) ( ) SubSpace of X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopStruct ) ) ;
end;

registration
let X be ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ;
cluster non empty strict TopSpace-like open dense for ( ( ) ( ) SubSpace of X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopStruct ) ) ;
end;

theorem :: TEX_3:23
for X being ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace)
for A0 being ( ( non empty ) ( non empty ) Subset of ) st A0 : ( ( non empty ) ( non empty ) Subset of ) is dense & A0 : ( ( non empty ) ( non empty ) Subset of ) is open holds
ex X0 being ( ( non empty strict open dense ) ( non empty strict TopSpace-like open dense everywhere_dense ) SubSpace of X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) st A0 : ( ( non empty ) ( non empty ) Subset of ) = the carrier of X0 : ( ( non empty strict open dense ) ( non empty strict TopSpace-like open dense everywhere_dense ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) : ( ( ) ( non empty ) set ) ;

theorem :: TEX_3:24
for X being ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace)
for X0 being ( ( ) ( TopSpace-like ) SubSpace of X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) holds
( X0 : ( ( ) ( TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) is everywhere_dense iff ex X1 being ( ( strict open dense ) ( strict TopSpace-like open dense everywhere_dense ) SubSpace of X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) st X1 : ( ( strict open dense ) ( strict TopSpace-like open dense everywhere_dense ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) is ( ( ) ( TopSpace-like ) SubSpace of X0 : ( ( ) ( TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) ) ) ;

theorem :: TEX_3:25
for X being ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace)
for X1, X2 being ( ( non empty ) ( non empty TopSpace-like ) SubSpace of X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) st ( X1 : ( ( non empty ) ( non empty TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) is dense or X2 : ( ( non empty ) ( non empty TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) is dense ) holds
X1 : ( ( non empty ) ( non empty TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) union X2 : ( ( non empty ) ( non empty TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) : ( ( non empty strict ) ( non empty strict TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) is ( ( dense ) ( TopSpace-like dense ) SubSpace of X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) ;

theorem :: TEX_3:26
for X being ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace)
for X1, X2 being ( ( non empty ) ( non empty TopSpace-like ) SubSpace of X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) st ( X1 : ( ( non empty ) ( non empty TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) is everywhere_dense or X2 : ( ( non empty ) ( non empty TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) is everywhere_dense ) holds
X1 : ( ( non empty ) ( non empty TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) union X2 : ( ( non empty ) ( non empty TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) : ( ( non empty strict ) ( non empty strict TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) is ( ( everywhere_dense ) ( TopSpace-like dense everywhere_dense ) SubSpace of X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) ;

theorem :: TEX_3:27
for X being ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace)
for X1, X2 being ( ( non empty ) ( non empty TopSpace-like ) SubSpace of X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) st X1 : ( ( non empty ) ( non empty TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) is everywhere_dense & X2 : ( ( non empty ) ( non empty TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) is everywhere_dense holds
X1 : ( ( non empty ) ( non empty TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) meet X2 : ( ( non empty ) ( non empty TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) : ( ( non empty strict ) ( non empty strict TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) is ( ( everywhere_dense ) ( TopSpace-like dense everywhere_dense ) SubSpace of X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) ;

theorem :: TEX_3:28
for X being ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace)
for X1, X2 being ( ( non empty ) ( non empty TopSpace-like ) SubSpace of X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) st ( ( X1 : ( ( non empty ) ( non empty TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) is everywhere_dense & X2 : ( ( non empty ) ( non empty TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) is dense ) or ( X1 : ( ( non empty ) ( non empty TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) is dense & X2 : ( ( non empty ) ( non empty TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) is everywhere_dense ) ) holds
X1 : ( ( non empty ) ( non empty TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) meet X2 : ( ( non empty ) ( non empty TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) : ( ( non empty strict ) ( non empty strict TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) is ( ( dense ) ( TopSpace-like dense ) SubSpace of X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) ;

begin

definition
let X be ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ;
let IT be ( ( ) ( TopSpace-like ) SubSpace of X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) ;
attr IT is boundary means :: TEX_3:def 3
for A being ( ( ) ( ) Subset of ) st A : ( ( ) ( ) Subset of ) = the carrier of IT : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopStruct ) : ( ( ) ( non empty ) set ) holds
A : ( ( ) ( ) Subset of ) is boundary ;
end;

theorem :: TEX_3:29
for X being ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace)
for X0 being ( ( ) ( TopSpace-like ) SubSpace of X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) )
for A being ( ( ) ( ) Subset of ) st A : ( ( ) ( ) Subset of ) = the carrier of X0 : ( ( ) ( TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) : ( ( ) ( ) set ) holds
( X0 : ( ( ) ( TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) is boundary iff A : ( ( ) ( ) Subset of ) is boundary ) ;

registration
let X be ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ;
cluster non empty open -> non empty non boundary for ( ( ) ( ) SubSpace of X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopStruct ) ) ;
cluster non empty boundary -> non empty non open for ( ( ) ( ) SubSpace of X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopStruct ) ) ;
cluster everywhere_dense -> non boundary for ( ( ) ( ) SubSpace of X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopStruct ) ) ;
cluster boundary -> non everywhere_dense for ( ( ) ( ) SubSpace of X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopStruct ) ) ;
end;

theorem :: TEX_3:30
for X being ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace)
for A0 being ( ( non empty ) ( non empty ) Subset of ) st A0 : ( ( non empty ) ( non empty ) Subset of ) is boundary holds
ex X0 being ( ( strict ) ( strict TopSpace-like ) SubSpace of X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) st
( X0 : ( ( strict ) ( strict TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) is boundary & A0 : ( ( non empty ) ( non empty ) Subset of ) = the carrier of X0 : ( ( strict ) ( strict TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) : ( ( ) ( ) set ) ) ;

theorem :: TEX_3:31
for X being ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace)
for X1, X2 being ( ( ) ( TopSpace-like ) SubSpace of X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) st X1 : ( ( ) ( TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) ,X2 : ( ( ) ( TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) constitute_a_decomposition holds
( X1 : ( ( ) ( TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) is dense iff X2 : ( ( ) ( TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) is boundary ) ;

theorem :: TEX_3:32
for X being ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace)
for X1, X2 being ( ( non empty ) ( non empty TopSpace-like ) SubSpace of X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) st X1 : ( ( non empty ) ( non empty TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) ,X2 : ( ( non empty ) ( non empty TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) constitute_a_decomposition holds
( X1 : ( ( non empty ) ( non empty TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) is boundary iff X2 : ( ( non empty ) ( non empty TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) is dense ) ;

theorem :: TEX_3:33
for X being ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace)
for X0 being ( ( ) ( TopSpace-like ) SubSpace of X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) st X0 : ( ( ) ( TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) is boundary holds
for A being ( ( ) ( ) Subset of ) st A : ( ( ) ( ) Subset of ) c= the carrier of X0 : ( ( ) ( TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) : ( ( ) ( ) set ) holds
A : ( ( ) ( ) Subset of ) is boundary ;

theorem :: TEX_3:34
for X being ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace)
for X1, X2 being ( ( ) ( TopSpace-like ) SubSpace of X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) st X1 : ( ( ) ( TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) is boundary & X2 : ( ( ) ( TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) is ( ( ) ( TopSpace-like ) SubSpace of X1 : ( ( ) ( TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) ) holds
X2 : ( ( ) ( TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) is boundary ;

definition
let X be ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ;
let IT be ( ( ) ( TopSpace-like ) SubSpace of X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) ;
attr IT is nowhere_dense means :: TEX_3:def 4
for A being ( ( ) ( ) Subset of ) st A : ( ( ) ( ) Subset of ) = the carrier of IT : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopStruct ) : ( ( ) ( non empty ) set ) holds
A : ( ( ) ( ) Subset of ) is nowhere_dense ;
end;

theorem :: TEX_3:35
for X being ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace)
for X0 being ( ( ) ( TopSpace-like ) SubSpace of X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) )
for A being ( ( ) ( ) Subset of ) st A : ( ( ) ( ) Subset of ) = the carrier of X0 : ( ( ) ( TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) : ( ( ) ( ) set ) holds
( X0 : ( ( ) ( TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) is nowhere_dense iff A : ( ( ) ( ) Subset of ) is nowhere_dense ) ;

registration
let X be ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ;
cluster nowhere_dense -> boundary for ( ( ) ( ) SubSpace of X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopStruct ) ) ;
cluster non boundary -> non nowhere_dense for ( ( ) ( ) SubSpace of X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopStruct ) ) ;
cluster nowhere_dense -> non dense for ( ( ) ( ) SubSpace of X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopStruct ) ) ;
cluster dense -> non nowhere_dense for ( ( ) ( ) SubSpace of X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopStruct ) ) ;
end;

theorem :: TEX_3:36
for X being ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace)
for A0 being ( ( non empty ) ( non empty ) Subset of ) st A0 : ( ( non empty ) ( non empty ) Subset of ) is nowhere_dense holds
ex X0 being ( ( strict ) ( strict TopSpace-like ) SubSpace of X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) st
( X0 : ( ( strict ) ( strict TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) is nowhere_dense & A0 : ( ( non empty ) ( non empty ) Subset of ) = the carrier of X0 : ( ( strict ) ( strict TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) : ( ( ) ( ) set ) ) ;

theorem :: TEX_3:37
for X being ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace)
for X1, X2 being ( ( ) ( TopSpace-like ) SubSpace of X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) st X1 : ( ( ) ( TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) ,X2 : ( ( ) ( TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) constitute_a_decomposition holds
( X1 : ( ( ) ( TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) is everywhere_dense iff X2 : ( ( ) ( TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) is nowhere_dense ) ;

theorem :: TEX_3:38
for X being ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace)
for X1, X2 being ( ( non empty ) ( non empty TopSpace-like ) SubSpace of X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) st X1 : ( ( non empty ) ( non empty TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) ,X2 : ( ( non empty ) ( non empty TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) constitute_a_decomposition holds
( X1 : ( ( non empty ) ( non empty TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) is nowhere_dense iff X2 : ( ( non empty ) ( non empty TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) is everywhere_dense ) ;

theorem :: TEX_3:39
for X being ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace)
for X0 being ( ( ) ( TopSpace-like ) SubSpace of X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) st X0 : ( ( ) ( TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) is nowhere_dense holds
for A being ( ( ) ( ) Subset of ) st A : ( ( ) ( ) Subset of ) c= the carrier of X0 : ( ( ) ( TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) : ( ( ) ( ) set ) holds
A : ( ( ) ( ) Subset of ) is nowhere_dense ;

theorem :: TEX_3:40
for X being ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace)
for X1, X2 being ( ( ) ( TopSpace-like ) SubSpace of X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) st X1 : ( ( ) ( TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) is nowhere_dense & X2 : ( ( ) ( TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) is ( ( ) ( TopSpace-like ) SubSpace of X1 : ( ( ) ( TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) ) holds
X2 : ( ( ) ( TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) is nowhere_dense ;

registration
let X be ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ;
cluster closed boundary -> nowhere_dense for ( ( ) ( ) SubSpace of X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopStruct ) ) ;
cluster boundary non nowhere_dense -> non closed for ( ( ) ( ) SubSpace of X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopStruct ) ) ;
cluster closed non nowhere_dense -> non boundary for ( ( ) ( ) SubSpace of X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopStruct ) ) ;
end;

theorem :: TEX_3:41
for X being ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace)
for A0 being ( ( non empty ) ( non empty ) Subset of ) st A0 : ( ( non empty ) ( non empty ) Subset of ) is boundary & A0 : ( ( non empty ) ( non empty ) Subset of ) is closed holds
ex X0 being ( ( non empty strict closed ) ( non empty strict TopSpace-like closed ) SubSpace of X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) st
( X0 : ( ( non empty strict closed ) ( non empty strict TopSpace-like closed ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) is boundary & A0 : ( ( non empty ) ( non empty ) Subset of ) = the carrier of X0 : ( ( non empty strict closed ) ( non empty strict TopSpace-like closed ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) : ( ( ) ( non empty ) set ) ) ;

theorem :: TEX_3:42
for X being ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace)
for X0 being ( ( non empty ) ( non empty TopSpace-like ) SubSpace of X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) holds
( X0 : ( ( non empty ) ( non empty TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) is nowhere_dense iff ex X1 being ( ( non empty strict closed ) ( non empty strict TopSpace-like closed ) SubSpace of X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) st
( X1 : ( ( non empty strict closed ) ( non empty strict TopSpace-like closed ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) is boundary & X0 : ( ( non empty ) ( non empty TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) is ( ( ) ( TopSpace-like ) SubSpace of X1 : ( ( non empty strict closed ) ( non empty strict TopSpace-like closed ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) ) ) ) ;

theorem :: TEX_3:43
for X being ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace)
for X1, X2 being ( ( non empty ) ( non empty TopSpace-like ) SubSpace of X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) st ( X1 : ( ( non empty ) ( non empty TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) is boundary or X2 : ( ( non empty ) ( non empty TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) is boundary ) & X1 : ( ( non empty ) ( non empty TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) meets X2 : ( ( non empty ) ( non empty TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) holds
X1 : ( ( non empty ) ( non empty TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) meet X2 : ( ( non empty ) ( non empty TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) : ( ( non empty strict ) ( non empty strict TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) is boundary ;

theorem :: TEX_3:44
for X being ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace)
for X1, X2 being ( ( non empty ) ( non empty TopSpace-like ) SubSpace of X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) st X1 : ( ( non empty ) ( non empty TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) is nowhere_dense & X2 : ( ( non empty ) ( non empty TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) is nowhere_dense holds
X1 : ( ( non empty ) ( non empty TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) union X2 : ( ( non empty ) ( non empty TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) : ( ( non empty strict ) ( non empty strict TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) is nowhere_dense ;

theorem :: TEX_3:45
for X being ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace)
for X1, X2 being ( ( non empty ) ( non empty TopSpace-like ) SubSpace of X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) st ( ( X1 : ( ( non empty ) ( non empty TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) is nowhere_dense & X2 : ( ( non empty ) ( non empty TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) is boundary ) or ( X1 : ( ( non empty ) ( non empty TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) is boundary & X2 : ( ( non empty ) ( non empty TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) is nowhere_dense ) ) holds
X1 : ( ( non empty ) ( non empty TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) union X2 : ( ( non empty ) ( non empty TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) : ( ( non empty strict ) ( non empty strict TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) is boundary ;

theorem :: TEX_3:46
for X being ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace)
for X1, X2 being ( ( non empty ) ( non empty TopSpace-like ) SubSpace of X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) st ( X1 : ( ( non empty ) ( non empty TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) is nowhere_dense or X2 : ( ( non empty ) ( non empty TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) is nowhere_dense ) & X1 : ( ( non empty ) ( non empty TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) meets X2 : ( ( non empty ) ( non empty TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) holds
X1 : ( ( non empty ) ( non empty TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) meet X2 : ( ( non empty ) ( non empty TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) : ( ( non empty strict ) ( non empty strict TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) is nowhere_dense ;

begin

theorem :: TEX_3:47
for X being ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) st ( for X0 being ( ( ) ( TopSpace-like ) SubSpace of X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) holds not X0 : ( ( ) ( TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) is boundary ) holds
X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) is discrete ;

theorem :: TEX_3:48
for X being ( ( non trivial TopSpace-like ) ( non empty non trivial TopSpace-like ) TopSpace) st ( for X0 being ( ( proper ) ( TopSpace-like proper ) SubSpace of X : ( ( non trivial TopSpace-like ) ( non empty non trivial TopSpace-like ) TopSpace) ) holds not X0 : ( ( proper ) ( TopSpace-like proper ) SubSpace of b1 : ( ( non trivial TopSpace-like ) ( non empty non trivial TopSpace-like ) TopSpace) ) is dense ) holds
X : ( ( non trivial TopSpace-like ) ( non empty non trivial TopSpace-like ) TopSpace) is discrete ;

registration
let X be ( ( non empty TopSpace-like discrete ) ( non empty TopSpace-like discrete almost_discrete extremally_disconnected hereditarily_extremally_disconnected ) TopSpace) ;
cluster non empty -> non empty non boundary for ( ( ) ( ) SubSpace of X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopStruct ) ) ;
cluster proper -> non dense for ( ( ) ( ) SubSpace of X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopStruct ) ) ;
cluster dense -> non proper for ( ( ) ( ) SubSpace of X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopStruct ) ) ;
end;

registration
let X be ( ( non empty TopSpace-like discrete ) ( non empty TopSpace-like discrete almost_discrete extremally_disconnected hereditarily_extremally_disconnected ) TopSpace) ;
cluster non empty strict TopSpace-like closed open discrete almost_discrete non boundary for ( ( ) ( ) SubSpace of X : ( ( non empty TopSpace-like discrete ) ( non empty TopSpace-like discrete almost_discrete extremally_disconnected hereditarily_extremally_disconnected ) TopStruct ) ) ;
end;

registration
let X be ( ( non trivial TopSpace-like discrete ) ( non empty non trivial TopSpace-like discrete almost_discrete extremally_disconnected hereditarily_extremally_disconnected ) TopSpace) ;
cluster strict TopSpace-like closed open discrete almost_discrete non dense for ( ( ) ( ) SubSpace of X : ( ( non trivial TopSpace-like discrete ) ( non empty non trivial TopSpace-like discrete almost_discrete extremally_disconnected hereditarily_extremally_disconnected ) TopStruct ) ) ;
end;

theorem :: TEX_3:49
for X being ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) st ex X0 being ( ( non empty ) ( non empty TopSpace-like ) SubSpace of X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) st X0 : ( ( non empty ) ( non empty TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) is boundary holds
not X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) is discrete ;

theorem :: TEX_3:50
for X being ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) st ex X0 being ( ( non empty ) ( non empty TopSpace-like ) SubSpace of X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) st
( X0 : ( ( non empty ) ( non empty TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) is dense & X0 : ( ( non empty ) ( non empty TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) is proper ) holds
not X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) is discrete ;

registration
let X be ( ( non empty TopSpace-like non discrete ) ( non empty non trivial TopSpace-like non discrete ) TopSpace) ;
cluster non empty strict TopSpace-like boundary for ( ( ) ( ) SubSpace of X : ( ( non empty TopSpace-like non discrete ) ( non empty non trivial TopSpace-like non discrete ) TopStruct ) ) ;
cluster non empty strict TopSpace-like proper dense for ( ( ) ( ) SubSpace of X : ( ( non empty TopSpace-like non discrete ) ( non empty non trivial TopSpace-like non discrete ) TopStruct ) ) ;
end;

theorem :: TEX_3:51
for X being ( ( non empty TopSpace-like non discrete ) ( non empty non trivial TopSpace-like non discrete ) TopSpace)
for A0 being ( ( non empty ) ( non empty ) Subset of ) st A0 : ( ( non empty ) ( non empty ) Subset of ) is boundary holds
ex X0 being ( ( strict boundary ) ( strict TopSpace-like proper non everywhere_dense boundary ) SubSpace of X : ( ( non empty TopSpace-like non discrete ) ( non empty non trivial TopSpace-like non discrete ) TopSpace) ) st A0 : ( ( non empty ) ( non empty ) Subset of ) = the carrier of X0 : ( ( strict boundary ) ( strict TopSpace-like proper non everywhere_dense boundary ) SubSpace of b1 : ( ( non empty TopSpace-like non discrete ) ( non empty non trivial TopSpace-like non discrete ) TopSpace) ) : ( ( ) ( ) set ) ;

theorem :: TEX_3:52
for X being ( ( non empty TopSpace-like non discrete ) ( non empty non trivial TopSpace-like non discrete ) TopSpace)
for A0 being ( ( non empty proper ) ( non empty proper ) Subset of ) st A0 : ( ( non empty proper ) ( non empty proper ) Subset of ) is dense holds
ex X0 being ( ( strict proper dense ) ( strict TopSpace-like non closed proper dense non nowhere_dense ) SubSpace of X : ( ( non empty TopSpace-like non discrete ) ( non empty non trivial TopSpace-like non discrete ) TopSpace) ) st A0 : ( ( non empty proper ) ( non empty proper ) Subset of ) = the carrier of X0 : ( ( strict proper dense ) ( strict TopSpace-like non closed proper dense non nowhere_dense ) SubSpace of b1 : ( ( non empty TopSpace-like non discrete ) ( non empty non trivial TopSpace-like non discrete ) TopSpace) ) : ( ( ) ( ) set ) ;

theorem :: TEX_3:53
for X being ( ( non empty TopSpace-like non discrete ) ( non empty non trivial TopSpace-like non discrete ) TopSpace)
for X1 being ( ( non empty boundary ) ( non empty TopSpace-like non open proper non everywhere_dense boundary ) SubSpace of X : ( ( non empty TopSpace-like non discrete ) ( non empty non trivial TopSpace-like non discrete ) TopSpace) ) ex X2 being ( ( non empty strict proper dense ) ( non empty strict TopSpace-like non closed proper dense non nowhere_dense ) SubSpace of X : ( ( non empty TopSpace-like non discrete ) ( non empty non trivial TopSpace-like non discrete ) TopSpace) ) st X1 : ( ( non empty boundary ) ( non empty TopSpace-like non open proper non everywhere_dense boundary ) SubSpace of b1 : ( ( non empty TopSpace-like non discrete ) ( non empty non trivial TopSpace-like non discrete ) TopSpace) ) ,X2 : ( ( non empty strict proper dense ) ( non empty strict TopSpace-like non closed proper dense non nowhere_dense ) SubSpace of b1 : ( ( non empty TopSpace-like non discrete ) ( non empty non trivial TopSpace-like non discrete ) TopSpace) ) constitute_a_decomposition ;

theorem :: TEX_3:54
for X being ( ( non empty TopSpace-like non discrete ) ( non empty non trivial TopSpace-like non discrete ) TopSpace)
for X1 being ( ( non empty proper dense ) ( non empty TopSpace-like non closed proper dense non nowhere_dense ) SubSpace of X : ( ( non empty TopSpace-like non discrete ) ( non empty non trivial TopSpace-like non discrete ) TopSpace) ) ex X2 being ( ( non empty strict boundary ) ( non empty strict TopSpace-like non open proper non everywhere_dense boundary ) SubSpace of X : ( ( non empty TopSpace-like non discrete ) ( non empty non trivial TopSpace-like non discrete ) TopSpace) ) st X1 : ( ( non empty proper dense ) ( non empty TopSpace-like non closed proper dense non nowhere_dense ) SubSpace of b1 : ( ( non empty TopSpace-like non discrete ) ( non empty non trivial TopSpace-like non discrete ) TopSpace) ) ,X2 : ( ( non empty strict boundary ) ( non empty strict TopSpace-like non open proper non everywhere_dense boundary ) SubSpace of b1 : ( ( non empty TopSpace-like non discrete ) ( non empty non trivial TopSpace-like non discrete ) TopSpace) ) constitute_a_decomposition ;

theorem :: TEX_3:55
for X being ( ( non empty TopSpace-like non discrete ) ( non empty non trivial TopSpace-like non discrete ) TopSpace)
for Y1, Y2 being ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) st Y2 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) = TopStruct(# the carrier of Y1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) : ( ( ) ( non empty ) set ) , the topology of Y1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) : ( ( ) ( non empty ) Element of K10(K10( the carrier of b2 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) : ( ( ) ( non empty ) set ) ) : ( ( ) ( ) set ) ) : ( ( ) ( ) set ) ) #) : ( ( strict ) ( non empty strict TopSpace-like ) TopStruct ) holds
( Y1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) is ( ( boundary ) ( TopSpace-like proper non everywhere_dense boundary ) SubSpace of X : ( ( non empty TopSpace-like non discrete ) ( non empty non trivial TopSpace-like non discrete ) TopSpace) ) iff Y2 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) is ( ( boundary ) ( TopSpace-like proper non everywhere_dense boundary ) SubSpace of X : ( ( non empty TopSpace-like non discrete ) ( non empty non trivial TopSpace-like non discrete ) TopSpace) ) ) ;

begin

theorem :: TEX_3:56
for X being ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) st ( for X0 being ( ( ) ( TopSpace-like ) SubSpace of X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) holds not X0 : ( ( ) ( TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) is nowhere_dense ) holds
X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) is almost_discrete ;

theorem :: TEX_3:57
for X being ( ( non trivial TopSpace-like ) ( non empty non trivial TopSpace-like ) TopSpace) st ( for X0 being ( ( proper ) ( TopSpace-like proper ) SubSpace of X : ( ( non trivial TopSpace-like ) ( non empty non trivial TopSpace-like ) TopSpace) ) holds not X0 : ( ( proper ) ( TopSpace-like proper ) SubSpace of b1 : ( ( non trivial TopSpace-like ) ( non empty non trivial TopSpace-like ) TopSpace) ) is everywhere_dense ) holds
X : ( ( non trivial TopSpace-like ) ( non empty non trivial TopSpace-like ) TopSpace) is almost_discrete ;

registration
let X be ( ( non empty TopSpace-like almost_discrete ) ( non empty TopSpace-like almost_discrete extremally_disconnected hereditarily_extremally_disconnected ) TopSpace) ;
cluster non empty -> non empty non nowhere_dense for ( ( ) ( ) SubSpace of X : ( ( non empty TopSpace-like non discrete ) ( non empty non trivial TopSpace-like non discrete ) TopStruct ) ) ;
cluster proper -> non everywhere_dense for ( ( ) ( ) SubSpace of X : ( ( non empty TopSpace-like non discrete ) ( non empty non trivial TopSpace-like non discrete ) TopStruct ) ) ;
cluster everywhere_dense -> non proper for ( ( ) ( ) SubSpace of X : ( ( non empty TopSpace-like non discrete ) ( non empty non trivial TopSpace-like non discrete ) TopStruct ) ) ;
cluster non empty boundary -> non empty non closed for ( ( ) ( ) SubSpace of X : ( ( non empty TopSpace-like non discrete ) ( non empty non trivial TopSpace-like non discrete ) TopStruct ) ) ;
cluster non empty closed -> non empty non boundary for ( ( ) ( ) SubSpace of X : ( ( non empty TopSpace-like non discrete ) ( non empty non trivial TopSpace-like non discrete ) TopStruct ) ) ;
cluster proper dense -> non open for ( ( ) ( ) SubSpace of X : ( ( non empty TopSpace-like non discrete ) ( non empty non trivial TopSpace-like non discrete ) TopStruct ) ) ;
cluster open dense -> non proper for ( ( ) ( ) SubSpace of X : ( ( non empty TopSpace-like non discrete ) ( non empty non trivial TopSpace-like non discrete ) TopStruct ) ) ;
cluster open proper -> non dense for ( ( ) ( ) SubSpace of X : ( ( non empty TopSpace-like non discrete ) ( non empty non trivial TopSpace-like non discrete ) TopStruct ) ) ;
end;

registration
let X be ( ( non empty TopSpace-like almost_discrete ) ( non empty TopSpace-like almost_discrete extremally_disconnected hereditarily_extremally_disconnected ) TopSpace) ;
cluster non empty strict TopSpace-like non nowhere_dense for ( ( ) ( ) SubSpace of X : ( ( non empty TopSpace-like almost_discrete ) ( non empty TopSpace-like almost_discrete extremally_disconnected hereditarily_extremally_disconnected ) TopStruct ) ) ;
end;

registration
let X be ( ( non trivial TopSpace-like almost_discrete ) ( non empty non trivial TopSpace-like almost_discrete extremally_disconnected hereditarily_extremally_disconnected ) TopSpace) ;
cluster strict TopSpace-like non everywhere_dense for ( ( ) ( ) SubSpace of X : ( ( non trivial TopSpace-like almost_discrete ) ( non empty non trivial TopSpace-like almost_discrete extremally_disconnected hereditarily_extremally_disconnected ) TopStruct ) ) ;
end;

theorem :: TEX_3:58
for X being ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) st ex X0 being ( ( non empty ) ( non empty TopSpace-like ) SubSpace of X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) st X0 : ( ( non empty ) ( non empty TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) is nowhere_dense holds
not X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) is almost_discrete ;

theorem :: TEX_3:59
for X being ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) st ex X0 being ( ( non empty ) ( non empty TopSpace-like ) SubSpace of X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) st
( X0 : ( ( non empty ) ( non empty TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) is boundary & X0 : ( ( non empty ) ( non empty TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) is closed ) holds
not X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) is almost_discrete ;

theorem :: TEX_3:60
for X being ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) st ex X0 being ( ( non empty ) ( non empty TopSpace-like ) SubSpace of X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) st
( X0 : ( ( non empty ) ( non empty TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) is everywhere_dense & X0 : ( ( non empty ) ( non empty TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) is proper ) holds
not X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) is almost_discrete ;

theorem :: TEX_3:61
for X being ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) st ex X0 being ( ( non empty ) ( non empty TopSpace-like ) SubSpace of X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) st
( X0 : ( ( non empty ) ( non empty TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) is dense & X0 : ( ( non empty ) ( non empty TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) is open & X0 : ( ( non empty ) ( non empty TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) ) is proper ) holds
not X : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) is almost_discrete ;

registration
let X be ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopSpace) ;
cluster non empty strict TopSpace-like nowhere_dense for ( ( ) ( ) SubSpace of X : ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopStruct ) ) ;
cluster non empty strict TopSpace-like proper everywhere_dense for ( ( ) ( ) SubSpace of X : ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopStruct ) ) ;
end;

theorem :: TEX_3:62
for X being ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopSpace)
for A0 being ( ( non empty ) ( non empty ) Subset of ) st A0 : ( ( non empty ) ( non empty ) Subset of ) is nowhere_dense holds
ex X0 being ( ( non empty strict nowhere_dense ) ( non empty strict TopSpace-like non open proper non dense non everywhere_dense boundary nowhere_dense ) SubSpace of X : ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopSpace) ) st A0 : ( ( non empty ) ( non empty ) Subset of ) = the carrier of X0 : ( ( non empty strict nowhere_dense ) ( non empty strict TopSpace-like non open proper non dense non everywhere_dense boundary nowhere_dense ) SubSpace of b1 : ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopSpace) ) : ( ( ) ( non empty ) set ) ;

theorem :: TEX_3:63
for X being ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopSpace)
for A0 being ( ( non empty proper ) ( non empty proper ) Subset of ) st A0 : ( ( non empty proper ) ( non empty proper ) Subset of ) is everywhere_dense holds
ex X0 being ( ( strict proper everywhere_dense ) ( strict TopSpace-like non closed proper dense everywhere_dense non boundary non nowhere_dense ) SubSpace of X : ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopSpace) ) st A0 : ( ( non empty proper ) ( non empty proper ) Subset of ) = the carrier of X0 : ( ( strict proper everywhere_dense ) ( strict TopSpace-like non closed proper dense everywhere_dense non boundary non nowhere_dense ) SubSpace of b1 : ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopSpace) ) : ( ( ) ( ) set ) ;

theorem :: TEX_3:64
for X being ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopSpace)
for X1 being ( ( non empty nowhere_dense ) ( non empty TopSpace-like non open proper non dense non everywhere_dense boundary nowhere_dense ) SubSpace of X : ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopSpace) ) ex X2 being ( ( non empty strict proper everywhere_dense ) ( non empty strict TopSpace-like non closed proper dense everywhere_dense non boundary non nowhere_dense ) SubSpace of X : ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopSpace) ) st X1 : ( ( non empty nowhere_dense ) ( non empty TopSpace-like non open proper non dense non everywhere_dense boundary nowhere_dense ) SubSpace of b1 : ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopSpace) ) ,X2 : ( ( non empty strict proper everywhere_dense ) ( non empty strict TopSpace-like non closed proper dense everywhere_dense non boundary non nowhere_dense ) SubSpace of b1 : ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopSpace) ) constitute_a_decomposition ;

theorem :: TEX_3:65
for X being ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopSpace)
for X1 being ( ( non empty proper everywhere_dense ) ( non empty TopSpace-like non closed proper dense everywhere_dense non boundary non nowhere_dense ) SubSpace of X : ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopSpace) ) ex X2 being ( ( non empty strict nowhere_dense ) ( non empty strict TopSpace-like non open proper non dense non everywhere_dense boundary nowhere_dense ) SubSpace of X : ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopSpace) ) st X1 : ( ( non empty proper everywhere_dense ) ( non empty TopSpace-like non closed proper dense everywhere_dense non boundary non nowhere_dense ) SubSpace of b1 : ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopSpace) ) ,X2 : ( ( non empty strict nowhere_dense ) ( non empty strict TopSpace-like non open proper non dense non everywhere_dense boundary nowhere_dense ) SubSpace of b1 : ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopSpace) ) constitute_a_decomposition ;

theorem :: TEX_3:66
for X being ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopSpace)
for Y1, Y2 being ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) st Y2 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) = TopStruct(# the carrier of Y1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) : ( ( ) ( non empty ) set ) , the topology of Y1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) : ( ( ) ( non empty ) Element of K10(K10( the carrier of b2 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) : ( ( ) ( non empty ) set ) ) : ( ( ) ( ) set ) ) : ( ( ) ( ) set ) ) #) : ( ( strict ) ( non empty strict TopSpace-like ) TopStruct ) holds
( Y1 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) is ( ( nowhere_dense ) ( TopSpace-like proper non dense non everywhere_dense boundary nowhere_dense ) SubSpace of X : ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopSpace) ) iff Y2 : ( ( non empty TopSpace-like ) ( non empty TopSpace-like ) TopSpace) is ( ( nowhere_dense ) ( TopSpace-like proper non dense non everywhere_dense boundary nowhere_dense ) SubSpace of X : ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopSpace) ) ) ;

registration
let X be ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopSpace) ;
cluster non empty strict TopSpace-like closed boundary for ( ( ) ( ) SubSpace of X : ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopStruct ) ) ;
cluster non empty strict TopSpace-like open proper dense for ( ( ) ( ) SubSpace of X : ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopStruct ) ) ;
end;

theorem :: TEX_3:67
for X being ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopSpace)
for A0 being ( ( non empty ) ( non empty ) Subset of ) st A0 : ( ( non empty ) ( non empty ) Subset of ) is boundary & A0 : ( ( non empty ) ( non empty ) Subset of ) is closed holds
ex X0 being ( ( non empty strict closed boundary ) ( non empty strict TopSpace-like closed non open proper non dense non everywhere_dense boundary nowhere_dense ) SubSpace of X : ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopSpace) ) st A0 : ( ( non empty ) ( non empty ) Subset of ) = the carrier of X0 : ( ( non empty strict closed boundary ) ( non empty strict TopSpace-like closed non open proper non dense non everywhere_dense boundary nowhere_dense ) SubSpace of b1 : ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopSpace) ) : ( ( ) ( non empty ) set ) ;

theorem :: TEX_3:68
for X being ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopSpace)
for A0 being ( ( non empty proper ) ( non empty proper ) Subset of ) st A0 : ( ( non empty proper ) ( non empty proper ) Subset of ) is dense & A0 : ( ( non empty proper ) ( non empty proper ) Subset of ) is open holds
ex X0 being ( ( strict open proper dense ) ( strict TopSpace-like non closed open proper dense everywhere_dense non boundary non nowhere_dense ) SubSpace of X : ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopSpace) ) st A0 : ( ( non empty proper ) ( non empty proper ) Subset of ) = the carrier of X0 : ( ( strict open proper dense ) ( strict TopSpace-like non closed open proper dense everywhere_dense non boundary non nowhere_dense ) SubSpace of b1 : ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopSpace) ) : ( ( ) ( ) set ) ;

theorem :: TEX_3:69
for X being ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopSpace)
for X1 being ( ( non empty closed boundary ) ( non empty TopSpace-like closed non open proper non dense non everywhere_dense boundary nowhere_dense ) SubSpace of X : ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopSpace) ) ex X2 being ( ( non empty strict open proper dense ) ( non empty strict TopSpace-like non closed open proper dense everywhere_dense non boundary non nowhere_dense ) SubSpace of X : ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopSpace) ) st X1 : ( ( non empty closed boundary ) ( non empty TopSpace-like closed non open proper non dense non everywhere_dense boundary nowhere_dense ) SubSpace of b1 : ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopSpace) ) ,X2 : ( ( non empty strict open proper dense ) ( non empty strict TopSpace-like non closed open proper dense everywhere_dense non boundary non nowhere_dense ) SubSpace of b1 : ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopSpace) ) constitute_a_decomposition ;

theorem :: TEX_3:70
for X being ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopSpace)
for X1 being ( ( non empty open proper dense ) ( non empty TopSpace-like non closed open proper dense everywhere_dense non boundary non nowhere_dense ) SubSpace of X : ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopSpace) ) ex X2 being ( ( non empty strict closed boundary ) ( non empty strict TopSpace-like closed non open proper non dense non everywhere_dense boundary nowhere_dense ) SubSpace of X : ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopSpace) ) st X1 : ( ( non empty open proper dense ) ( non empty TopSpace-like non closed open proper dense everywhere_dense non boundary non nowhere_dense ) SubSpace of b1 : ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopSpace) ) ,X2 : ( ( non empty strict closed boundary ) ( non empty strict TopSpace-like closed non open proper non dense non everywhere_dense boundary nowhere_dense ) SubSpace of b1 : ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopSpace) ) constitute_a_decomposition ;

theorem :: TEX_3:71
for X being ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopSpace)
for X0 being ( ( non empty ) ( non empty TopSpace-like ) SubSpace of X : ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopSpace) ) holds
( X0 : ( ( non empty ) ( non empty TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopSpace) ) is nowhere_dense iff ex X1 being ( ( non empty strict closed boundary ) ( non empty strict TopSpace-like closed non open proper non dense non everywhere_dense boundary nowhere_dense ) SubSpace of X : ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopSpace) ) st X0 : ( ( non empty ) ( non empty TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopSpace) ) is ( ( ) ( TopSpace-like ) SubSpace of X1 : ( ( non empty strict closed boundary ) ( non empty strict TopSpace-like closed non open proper non dense non everywhere_dense boundary nowhere_dense ) SubSpace of b1 : ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopSpace) ) ) ) ;

theorem :: TEX_3:72
for X being ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopSpace)
for X0 being ( ( non empty nowhere_dense ) ( non empty TopSpace-like non open proper non dense non everywhere_dense boundary nowhere_dense ) SubSpace of X : ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopSpace) ) holds
( ( X0 : ( ( non empty nowhere_dense ) ( non empty TopSpace-like non open proper non dense non everywhere_dense boundary nowhere_dense ) SubSpace of b1 : ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopSpace) ) is boundary & X0 : ( ( non empty nowhere_dense ) ( non empty TopSpace-like non open proper non dense non everywhere_dense boundary nowhere_dense ) SubSpace of b1 : ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopSpace) ) is closed ) or ex X1 being ( ( non empty strict proper everywhere_dense ) ( non empty strict TopSpace-like non closed proper dense everywhere_dense non boundary non nowhere_dense ) SubSpace of X : ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopSpace) ) ex X2 being ( ( non empty strict closed boundary ) ( non empty strict TopSpace-like closed non open proper non dense non everywhere_dense boundary nowhere_dense ) SubSpace of X : ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopSpace) ) st
( X1 : ( ( non empty strict proper everywhere_dense ) ( non empty strict TopSpace-like non closed proper dense everywhere_dense non boundary non nowhere_dense ) SubSpace of b1 : ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopSpace) ) meet X2 : ( ( non empty strict closed boundary ) ( non empty strict TopSpace-like closed non open proper non dense non everywhere_dense boundary nowhere_dense ) SubSpace of b1 : ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopSpace) ) : ( ( non empty strict ) ( non empty strict TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopSpace) ) = TopStruct(# the carrier of X0 : ( ( non empty nowhere_dense ) ( non empty TopSpace-like non open proper non dense non everywhere_dense boundary nowhere_dense ) SubSpace of b1 : ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopSpace) ) : ( ( ) ( non empty ) set ) , the topology of X0 : ( ( non empty nowhere_dense ) ( non empty TopSpace-like non open proper non dense non everywhere_dense boundary nowhere_dense ) SubSpace of b1 : ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopSpace) ) : ( ( ) ( non empty ) Element of K10(K10( the carrier of b2 : ( ( non empty nowhere_dense ) ( non empty TopSpace-like non open proper non dense non everywhere_dense boundary nowhere_dense ) SubSpace of b1 : ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopSpace) ) : ( ( ) ( non empty ) set ) ) : ( ( ) ( ) set ) ) : ( ( ) ( ) set ) ) #) : ( ( strict ) ( non empty strict TopSpace-like ) TopStruct ) & X1 : ( ( non empty strict proper everywhere_dense ) ( non empty strict TopSpace-like non closed proper dense everywhere_dense non boundary non nowhere_dense ) SubSpace of b1 : ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopSpace) ) union X2 : ( ( non empty strict closed boundary ) ( non empty strict TopSpace-like closed non open proper non dense non everywhere_dense boundary nowhere_dense ) SubSpace of b1 : ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopSpace) ) : ( ( non empty strict ) ( non empty strict TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopSpace) ) = TopStruct(# the carrier of X : ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopSpace) : ( ( ) ( non empty non trivial ) set ) , the topology of X : ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopSpace) : ( ( ) ( non empty ) Element of K10(K10( the carrier of b1 : ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopSpace) : ( ( ) ( non empty non trivial ) set ) ) : ( ( ) ( ) set ) ) : ( ( ) ( ) set ) ) #) : ( ( strict ) ( non empty strict TopSpace-like ) TopStruct ) ) ) ;

theorem :: TEX_3:73
for X being ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopSpace)
for X0 being ( ( non empty everywhere_dense ) ( non empty TopSpace-like dense everywhere_dense non boundary non nowhere_dense ) SubSpace of X : ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopSpace) ) holds
( ( X0 : ( ( non empty everywhere_dense ) ( non empty TopSpace-like dense everywhere_dense non boundary non nowhere_dense ) SubSpace of b1 : ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopSpace) ) is dense & X0 : ( ( non empty everywhere_dense ) ( non empty TopSpace-like dense everywhere_dense non boundary non nowhere_dense ) SubSpace of b1 : ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopSpace) ) is open ) or ex X1 being ( ( non empty strict open proper dense ) ( non empty strict TopSpace-like non closed open proper dense everywhere_dense non boundary non nowhere_dense ) SubSpace of X : ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopSpace) ) ex X2 being ( ( non empty strict nowhere_dense ) ( non empty strict TopSpace-like non open proper non dense non everywhere_dense boundary nowhere_dense ) SubSpace of X : ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopSpace) ) st
( X1 : ( ( non empty strict open proper dense ) ( non empty strict TopSpace-like non closed open proper dense everywhere_dense non boundary non nowhere_dense ) SubSpace of b1 : ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopSpace) ) misses X2 : ( ( non empty strict nowhere_dense ) ( non empty strict TopSpace-like non open proper non dense non everywhere_dense boundary nowhere_dense ) SubSpace of b1 : ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopSpace) ) & X1 : ( ( non empty strict open proper dense ) ( non empty strict TopSpace-like non closed open proper dense everywhere_dense non boundary non nowhere_dense ) SubSpace of b1 : ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopSpace) ) union X2 : ( ( non empty strict nowhere_dense ) ( non empty strict TopSpace-like non open proper non dense non everywhere_dense boundary nowhere_dense ) SubSpace of b1 : ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopSpace) ) : ( ( non empty strict ) ( non empty strict TopSpace-like ) SubSpace of b1 : ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopSpace) ) = TopStruct(# the carrier of X0 : ( ( non empty everywhere_dense ) ( non empty TopSpace-like dense everywhere_dense non boundary non nowhere_dense ) SubSpace of b1 : ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopSpace) ) : ( ( ) ( non empty ) set ) , the topology of X0 : ( ( non empty everywhere_dense ) ( non empty TopSpace-like dense everywhere_dense non boundary non nowhere_dense ) SubSpace of b1 : ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopSpace) ) : ( ( ) ( non empty ) Element of K10(K10( the carrier of b2 : ( ( non empty everywhere_dense ) ( non empty TopSpace-like dense everywhere_dense non boundary non nowhere_dense ) SubSpace of b1 : ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopSpace) ) : ( ( ) ( non empty ) set ) ) : ( ( ) ( ) set ) ) : ( ( ) ( ) set ) ) #) : ( ( strict ) ( non empty strict TopSpace-like ) TopStruct ) ) ) ;

theorem :: TEX_3:74
for X being ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopSpace)
for X0 being ( ( non empty nowhere_dense ) ( non empty TopSpace-like non open proper non dense non everywhere_dense boundary nowhere_dense ) SubSpace of X : ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopSpace) ) ex X1 being ( ( non empty strict open proper dense ) ( non empty strict TopSpace-like non closed open proper dense everywhere_dense non boundary non nowhere_dense ) SubSpace of X : ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopSpace) ) ex X2 being ( ( non empty strict closed boundary ) ( non empty strict TopSpace-like closed non open proper non dense non everywhere_dense boundary nowhere_dense ) SubSpace of X : ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopSpace) ) st
( X1 : ( ( non empty strict open proper dense ) ( non empty strict TopSpace-like non closed open proper dense everywhere_dense non boundary non nowhere_dense ) SubSpace of b1 : ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopSpace) ) ,X2 : ( ( non empty strict closed boundary ) ( non empty strict TopSpace-like closed non open proper non dense non everywhere_dense boundary nowhere_dense ) SubSpace of b1 : ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopSpace) ) constitute_a_decomposition & X0 : ( ( non empty nowhere_dense ) ( non empty TopSpace-like non open proper non dense non everywhere_dense boundary nowhere_dense ) SubSpace of b1 : ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopSpace) ) is ( ( ) ( TopSpace-like ) SubSpace of X2 : ( ( non empty strict closed boundary ) ( non empty strict TopSpace-like closed non open proper non dense non everywhere_dense boundary nowhere_dense ) SubSpace of b1 : ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopSpace) ) ) ) ;

theorem :: TEX_3:75
for X being ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopSpace)
for X0 being ( ( proper everywhere_dense ) ( TopSpace-like non closed proper dense everywhere_dense non boundary non nowhere_dense ) SubSpace of X : ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopSpace) ) ex X1 being ( ( strict open proper dense ) ( strict TopSpace-like non closed open proper dense everywhere_dense non boundary non nowhere_dense ) SubSpace of X : ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopSpace) ) ex X2 being ( ( strict closed boundary ) ( strict TopSpace-like closed proper non dense non everywhere_dense boundary nowhere_dense ) SubSpace of X : ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopSpace) ) st
( X1 : ( ( strict open proper dense ) ( strict TopSpace-like non closed open proper dense everywhere_dense non boundary non nowhere_dense ) SubSpace of b1 : ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopSpace) ) ,X2 : ( ( strict closed boundary ) ( strict TopSpace-like closed proper non dense non everywhere_dense boundary nowhere_dense ) SubSpace of b1 : ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopSpace) ) constitute_a_decomposition & X1 : ( ( strict open proper dense ) ( strict TopSpace-like non closed open proper dense everywhere_dense non boundary non nowhere_dense ) SubSpace of b1 : ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopSpace) ) is ( ( ) ( TopSpace-like ) SubSpace of X0 : ( ( proper everywhere_dense ) ( TopSpace-like non closed proper dense everywhere_dense non boundary non nowhere_dense ) SubSpace of b1 : ( ( non empty TopSpace-like non almost_discrete ) ( non empty non trivial TopSpace-like non discrete non anti-discrete non almost_discrete ) TopSpace) ) ) ) ;