:: Hierarchies and Classifications of Sets
:: by Mariusz Giero
::
:: Received December 28, 2001
:: Copyright (c) 2001 Association of Mizar Users


begin

definition
let A be RelStr ;
attr A is with_superior means :: TAXONOM2:def 1
 ex x being Element of A st x is_superior_of the InternalRel of A;
end;

:: deftheorem defines with_superior TAXONOM2:def 1 :
for A being RelStr holds
( A is with_superior iff ex x being Element of A st x is_superior_of the InternalRel of A );

definition
let A be RelStr ;
attr A is with_comparable_down means :Def2: :: TAXONOM2:def 2
 for x, y being Element of A holds
( for z being Element of A holds
( not z <= x or not z <= y ) or x <= y or y <= x );
end;

:: deftheorem Def2 defines with_comparable_down TAXONOM2:def 2 :
for A being RelStr holds
( A is with_comparable_down iff for x, y being Element of A holds
( for z being Element of A holds
( not z <= x or not z <= y ) or x <= y or y <= x ) );

theorem Th1: :: TAXONOM2:1
for a being set holds
( not InclPoset {{a}} is empty & InclPoset {{a}} is reflexive & InclPoset {{a}} is transitive & InclPoset {{a}} is antisymmetric & InclPoset {{a}} is with_superior & InclPoset {{a}} is with_comparable_down )
proof end;

registration
cluster non empty strict reflexive transitive antisymmetric with_superior with_comparable_down RelStr ;
existence
ex b1 being RelStr st
( not b1 is empty & b1 is reflexive & b1 is transitive & b1 is antisymmetric & b1 is with_superior & b1 is with_comparable_down & b1 is strict )
proof end;
end;

definition
mode Tree is with_superior with_comparable_down Poset;
end;

theorem Th2: :: TAXONOM2:2
for X being non empty set
for EqR being Equivalence_Relation of X
for x, y, z being set st z in Class (EqR,x) & z in Class (EqR,y) holds
Class (EqR,x) = Class (EqR,y)
proof end;

theorem Th3: :: TAXONOM2:3
for X being non empty set
for P being a_partition of X
for x, y, z being set st x in P & y in P & z in x & z in y holds
x = y
proof end;

theorem Th4: :: TAXONOM2:4
for X being non empty set
for C, x being set st C is Classification of X & x in union C holds
x c= X
proof end;

theorem :: TAXONOM2:5
for X being non empty set
for C being set st C is Strong_Classification of X holds
InclPoset (union C) is Tree
proof end;

begin

definition
let Y be set ;
attr Y is hierarchic means :Def3: :: TAXONOM2:def 3
 for x, y being set st x in Y & y in Y & not x c= y & not y c= x holds
x misses y;
end;

:: deftheorem Def3 defines hierarchic TAXONOM2:def 3 :
for Y being set holds
( Y is hierarchic iff for x, y being set st x in Y & y in Y & not x c= y & not y c= x holds
x misses y );

registration
cluster trivial -> hierarchic set ;
coherence
for b1 being set st b1 is trivial holds
b1 is hierarchic
proof end;
end;

registration
cluster non trivial hierarchic set ;
existence
ex b1 being set st
( not b1 is trivial & b1 is hierarchic )
proof end;
end;

theorem Th6: :: TAXONOM2:6
{} is hierarchic
proof end;

theorem :: TAXONOM2:7
{{}} is hierarchic
proof end;

definition
let Y be set ;
mode Hierarchy of Y -> Subset-Family of Y means :Def4: :: TAXONOM2:def 4
it is hierarchic ;
existence
ex b1 being Subset-Family of Y st b1 is hierarchic
proof end;
end;

:: deftheorem Def4 defines Hierarchy TAXONOM2:def 4 :
for Y being set
for b2 being Subset-Family of Y holds
( b2 is Hierarchy of Y iff b2 is hierarchic );

definition
let Y be set ;
attr Y is mutually-disjoint means :Def5: :: TAXONOM2:def 5
 for x, y being set st x in Y & y in Y & x <> y holds
x misses y;
end;

:: deftheorem Def5 defines mutually-disjoint TAXONOM2:def 5 :
for Y being set holds
( Y is mutually-disjoint iff for x, y being set st x in Y & y in Y & x <> y holds
x misses y );

Lm1: now
let x, y be set ; :: thesis: ( x in {{}} & y in {{}} & x <> y implies x misses y )
assume that
A1: x in {{}} and
A2: y in {{}} and
A3: x <> y ; :: thesis: x misses y
x = {} by A1, TARSKI:def 1;
hence x misses y by A2, A3, TARSKI:def 1; :: thesis: verum
end;

registration
let Y be set ;
cluster mutually-disjoint Element of bool (bool Y);
existence
ex b1 being Subset-Family of Y st b1 is mutually-disjoint
proof end;
end;

theorem :: TAXONOM2:8
{} is mutually-disjoint
proof end;

theorem :: TAXONOM2:9
{{}} is mutually-disjoint by Def5, Lm1;

theorem Th10: :: TAXONOM2:10
for a being set holds {a} is mutually-disjoint
proof end;

Lm2: now
let Y be set ; :: thesis: for H being Hierarchy of Y st H is covering holds
for B being mutually-disjoint Subset-Family of Y st B c= H & ( for C being mutually-disjoint Subset-Family of Y st C c= H & union B c= union C holds
B = C ) holds
union B = Y
let H be Hierarchy of Y; :: thesis: ( H is covering implies for B being mutually-disjoint Subset-Family of Y st B c= H & ( for C being mutually-disjoint Subset-Family of Y st C c= H & union B c= union C holds
B = C ) holds
union B = Y )
assume A1: H is covering ; :: thesis: for B being mutually-disjoint Subset-Family of Y st B c= H & ( for C being mutually-disjoint Subset-Family of Y st C c= H & union B c= union C holds
B = C ) holds
union B = Y
let B be mutually-disjoint Subset-Family of Y; :: thesis: ( B c= H & ( for C being mutually-disjoint Subset-Family of Y st C c= H & union B c= union C holds
B = C ) implies union B = Y )
assume that
A2: B c= H and
A3: for C being mutually-disjoint Subset-Family of Y st C c= H & union B c= union C holds
B = C ; :: thesis: union B = Y
Y c= union B
proof
let y be set ; :: according to TARSKI:def 3 :: thesis: ( not y in Y or y in union B )
assume y in Y ; :: thesis: y in union B
then y in union H by A1, ABIAN:4;
then consider x being set such that
A4: y in x and
A5: x in H by TARSKI:def 4;
now
defpred S1[ set ] means $1 c= x;
consider D being set such that
A6: for a being set holds
( a in D iff ( a in B & S1[a] ) ) from XBOOLE_0:sch 1();
set C = (B \ D) \/ {x};
A7: B \ D c= (B \ D) \/ {x} by XBOOLE_1:7;
A8: {x} c= H
proof
let s be set ; :: according to TARSKI:def 3 :: thesis: ( not s in {x} or s in H )
assume s in {x} ; :: thesis: s in H
hence s in H by A5, TARSKI:def 1; :: thesis: verum
end;
assume A9: not y in union B ; :: thesis: contradiction
A10: for p being set st p in B & not p in D & p <> x holds
p misses x
proof
A11: H is hierarchic by Def4;
let p be set ; :: thesis: ( p in B & not p in D & p <> x implies p misses x )
assume that
A12: p in B and
A13: not p in D and
p <> x ; :: thesis: p misses x
A14: not x c= p by A4, A9, A12, TARSKI:def 4;
not p c= x by A6, A12, A13;
hence p misses x by A2, A5, A12, A14, A11, Def3; :: thesis: verum
end;
A15: for p, q being set st p in (B \ D) \/ {x} & q in (B \ D) \/ {x} & p <> q holds
p misses q
proof
let p, q be set ; :: thesis: ( p in (B \ D) \/ {x} & q in (B \ D) \/ {x} & p <> q implies p misses q )
assume that
A16: p in (B \ D) \/ {x} and
A17: q in (B \ D) \/ {x} and
A18: p <> q ; :: thesis: p misses q
per cases ( p in B \ D or p in {x} ) by A16, XBOOLE_0:def 3;
suppose A19: p in B \ D ; :: thesis: p misses q
then A20: not p in D by XBOOLE_0:def 5;
A21: p in B by A19, XBOOLE_0:def 5;
per cases ( q in B \ D or q in {x} ) by A17, XBOOLE_0:def 3;
suppose q in B \ D ; :: thesis: p misses q
then q in B by XBOOLE_0:def 5;
hence p misses q by A18, A21, Def5; :: thesis: verum
end;
suppose q in {x} ; :: thesis: p misses q
then q = x by TARSKI:def 1;
hence p misses q by A10, A18, A21, A20; :: thesis: verum
end;
end;
end;
suppose p in {x} ; :: thesis: p misses q
then A22: p = x by TARSKI:def 1;
per cases ( q in B \ D or q in {x} ) by A17, XBOOLE_0:def 3;
suppose A23: q in B \ D ; :: thesis: p misses q
then A24: not q in D by XBOOLE_0:def 5;
q in B by A23, XBOOLE_0:def 5;
hence p misses q by A10, A18, A22, A24; :: thesis: verum
end;
suppose q in {x} ; :: thesis: p misses q
hence p misses q by A18, A22, TARSKI:def 1; :: thesis: verum
end;
end;
end;
end;
end;
x in {x} by TARSKI:def 1;
then A25: x in (B \ D) \/ {x} by XBOOLE_0:def 3;
A26: union B c= union ((B \ D) \/ {x})
proof
let s be set ; :: according to TARSKI:def 3 :: thesis: ( not s in union B or s in union ((B \ D) \/ {x}) )
assume s in union B ; :: thesis: s in union ((B \ D) \/ {x})
then consider t being set such that
A27: s in t and
A28: t in B by TARSKI:def 4;
per cases ( t in D or not t in D ) ;
suppose t in D ; :: thesis: s in union ((B \ D) \/ {x})
then t c= x by A6;
hence s in union ((B \ D) \/ {x}) by A25, A27, TARSKI:def 4; :: thesis: verum
end;
suppose not t in D ; :: thesis: s in union ((B \ D) \/ {x})
then t in B \ D by A28, XBOOLE_0:def 5;
hence s in union ((B \ D) \/ {x}) by A7, A27, TARSKI:def 4; :: thesis: verum
end;
end;
end;
A29: x in {x} by TARSKI:def 1;
B \ D c= B by XBOOLE_1:36;
then A30: B \ D c= H by A2, XBOOLE_1:1;
then (B \ D) \/ {x} c= H by A8, XBOOLE_1:8;
then (B \ D) \/ {x} is mutually-disjoint Subset-Family of Y by A15, Def5, XBOOLE_1:1;
then A31: B = (B \ D) \/ {x} by A3, A30, A8, A26, XBOOLE_1:8;
{x} c= (B \ D) \/ {x} by XBOOLE_1:7;
hence contradiction by A4, A9, A31, A29, TARSKI:def 4; :: thesis: verum
end;
hence y in union B ; :: thesis: verum
end;
hence union B = Y by XBOOLE_0:def 10; :: thesis: verum
end;

Lm3: now
let Y be set ; :: thesis: for H being Hierarchy of Y
for B being mutually-disjoint Subset-Family of Y st B c= H & ( for C being mutually-disjoint Subset-Family of Y st C c= H & union B c= union C holds
B = C ) holds
for S1 being Subset of Y st S1 in B holds
S1 <> {}
let H be Hierarchy of Y; :: thesis: for B being mutually-disjoint Subset-Family of Y st B c= H & ( for C being mutually-disjoint Subset-Family of Y st C c= H & union B c= union C holds
B = C ) holds
for S1 being Subset of Y st S1 in B holds
S1 <> {}
let B be mutually-disjoint Subset-Family of Y; :: thesis: ( B c= H & ( for C being mutually-disjoint Subset-Family of Y st C c= H & union B c= union C holds
B = C ) implies for S1 being Subset of Y st S1 in B holds
S1 <> {} )
assume that
A1: B c= H and
A2: for C being mutually-disjoint Subset-Family of Y st C c= H & union B c= union C holds
B = C ; :: thesis: for S1 being Subset of Y st S1 in B holds
S1 <> {}
let S1 be Subset of Y; :: thesis: ( S1 in B implies S1 <> {} )
assume A3: S1 in B ; :: thesis: S1 <> {}
now
set C = B \ {{}};
assume A4: S1 = {} ; :: thesis: contradiction
A5: union B c= union (B \ {{}})
proof
let x be set ; :: according to TARSKI:def 3 :: thesis: ( not x in union B or x in union (B \ {{}}) )
assume x in union B ; :: thesis: x in union (B \ {{}})
then consider y being set such that
A6: x in y and
A7: y in B by TARSKI:def 4;
not y in {{}} by A6, TARSKI:def 1;
then y in B \ {{}} by A7, XBOOLE_0:def 5;
hence x in union (B \ {{}}) by A6, TARSKI:def 4; :: thesis: verum
end;
A8: B \ {{}} is mutually-disjoint
proof
let x, y be set ; :: according to TAXONOM2:def 5 :: thesis: ( x in B \ {{}} & y in B \ {{}} & x <> y implies x misses y )
assume that
A9: x in B \ {{}} and
A10: y in B \ {{}} and
A11: x <> y ; :: thesis: x misses y
A12: y in B by A10, XBOOLE_0:def 5;
x in B by A9, XBOOLE_0:def 5;
hence x misses y by A11, A12, Def5; :: thesis: verum
end;
B \ {{}} c= B by XBOOLE_1:36;
then B \ {{}} c= H by A1, XBOOLE_1:1;
then B = B \ {{}} by A2, A5, A8;
then not {} in {{}} by A3, A4, XBOOLE_0:def 5;
hence contradiction by TARSKI:def 1; :: thesis: verum
end;
hence S1 <> {} ; :: thesis: verum
end;

definition
let Y be set ;
let F be Subset-Family of Y;
attr F is T_3 means :Def6: :: TAXONOM2:def 6
 for A being Subset of Y st A in F holds
for x being Element of Y st not x in A holds
ex B being Subset of Y st
( x in B & B in F & A misses B );
end;

:: deftheorem Def6 defines T_3 TAXONOM2:def 6 :
for Y being set
for F being Subset-Family of Y holds
( F is T_3 iff for A being Subset of Y st A in F holds
for x being Element of Y st not x in A holds
ex B being Subset of Y st
( x in B & B in F & A misses B ) );

theorem Th11: :: TAXONOM2:11
for Y being set
for F being Subset-Family of Y st F = {} holds
F is T_3
proof end;

registration
let Y be set ;
cluster covering T_3 Hierarchy of Y;
existence
ex b1 being Hierarchy of Y st
( b1 is covering & b1 is T_3 )
proof end;
end;

definition
let Y be set ;
let F be Subset-Family of Y;
attr F is lower-bounded means :Def7: :: TAXONOM2:def 7
 for B being set st B <> {} & B c= F & B is c=-linear holds
ex c being set st
( c in F & c c= meet B );
end;

:: deftheorem Def7 defines lower-bounded TAXONOM2:def 7 :
for Y being set
for F being Subset-Family of Y holds
( F is lower-bounded iff for B being set st B <> {} & B c= F & B is c=-linear holds
ex c being set st
( c in F & c c= meet B ) );

theorem Th12: :: TAXONOM2:12
for Y being set
for S1 being Subset of Y
for B being mutually-disjoint Subset-Family of Y st ( for b being set st b in B holds
( S1 misses b & Y <> {} ) ) holds
( B \/ {S1} is mutually-disjoint Subset-Family of Y & ( S1 <> {} implies union (B \/ {S1}) <> union B ) )
proof end;

definition
let Y be set ;
let F be Subset-Family of Y;
attr F is with_max's means :Def8: :: TAXONOM2:def 8
 for S being Subset of Y st S in F holds
ex T being Subset of Y st
( S c= T & T in F & ( for V being Subset of Y st T c= V & V in F holds
V = Y ) );
end;

:: deftheorem Def8 defines with_max's TAXONOM2:def 8 :
for Y being set
for F being Subset-Family of Y holds
( F is with_max's iff for S being Subset of Y st S in F holds
ex T being Subset of Y st
( S c= T & T in F & ( for V being Subset of Y st T c= V & V in F holds
V = Y ) ) );

begin

theorem :: TAXONOM2:13
for Y being set
for H being covering Hierarchy of Y st H is with_max's holds
ex P being a_partition of Y st P c= H
proof end;

theorem :: TAXONOM2:14
for Y being set
for H being covering Hierarchy of Y
for B being mutually-disjoint Subset-Family of Y st B c= H & ( for C being mutually-disjoint Subset-Family of Y st C c= H & union B c= union C holds
B = C ) holds
B is a_partition of Y
proof end;

theorem :: TAXONOM2:15
for Y being set
for H being covering T_3 Hierarchy of Y st H is lower-bounded & not {} in H holds
for A being Subset of Y
for B being mutually-disjoint Subset-Family of Y st A in B & B c= H & ( for C being mutually-disjoint Subset-Family of Y st A in C & C c= H & union B c= union C holds
union B = union C ) holds
B is a_partition of Y
proof end;

theorem Th16: :: TAXONOM2:16
for Y being set
for H being covering T_3 Hierarchy of Y st H is lower-bounded & not {} in H holds
for A being Subset of Y
for B being mutually-disjoint Subset-Family of Y st A in B & B c= H & ( for C being mutually-disjoint Subset-Family of Y st A in C & C c= H & B c= C holds
B = C ) holds
B is a_partition of Y
proof end;

theorem Th17: :: TAXONOM2:17
for Y being set
for H being covering T_3 Hierarchy of Y st H is lower-bounded & not {} in H holds
for A being Subset of Y st A in H holds
ex P being a_partition of Y st
( A in P & P c= H )
proof end;

Lm4: now
let x be non empty set ; :: thesis: for y being set st x c= y holds
x meets y
A1: ex a being set st a in x by XBOOLE_0:def 1;
let y be set ; :: thesis: ( x c= y implies x meets y )
assume x c= y ; :: thesis: x meets y
hence x meets y by A1, XBOOLE_0:3; :: thesis: verum
end;

theorem Th18: :: TAXONOM2:18
for X, h being non empty set
for Pmin being a_partition of X
for hw being set st hw in Pmin & h c= hw holds
for PS being a_partition of X st h in PS & ( for x being set holds
( not x in PS or x c= hw or hw c= x or hw misses x ) ) holds
for PT being set st ( for a being set holds
( a in PT iff ( a in PS & a c= hw ) ) ) holds
( PT \/ (Pmin \ {hw}) is a_partition of X & PT \/ (Pmin \ {hw}) is_finer_than Pmin )
proof end;

theorem Th19: :: TAXONOM2:19
for X, h being non empty set st h c= X holds
for Pmax being a_partition of X st ex hy being set st
( hy in Pmax & hy c= h ) & ( for x being set holds
( not x in Pmax or x c= h or h c= x or h misses x ) ) holds
for Pb being set st ( for x being set holds
( x in Pb iff ( x in Pmax & x misses h ) ) ) holds
( Pb \/ {h} is a_partition of X & Pmax is_finer_than Pb \/ {h} & ( for Pmin being a_partition of X st Pmax is_finer_than Pmin holds
for hw being set st hw in Pmin & h c= hw holds
Pb \/ {h} is_finer_than Pmin ) )
proof end;

theorem :: TAXONOM2:20
for X being non empty set
for H being covering T_3 Hierarchy of X st H is lower-bounded & not {} in H & ( for C1 being set st C1 <> {} & C1 c= PARTITIONS X & ( for P1, P2 being set st P1 in C1 & P2 in C1 & not P1 is_finer_than P2 holds
P2 is_finer_than P1 ) holds
ex PX, PY being set st
( PX in C1 & PY in C1 & ( for PZ being set st PZ in C1 holds
( PZ is_finer_than PY & PX is_finer_than PZ ) ) ) ) holds
ex C being Classification of X st union C = H
proof end;