:: MEASURE1 semantic presentation

theorem Th1: :: MEASURE1:1
for b1, b2 being set holds union {b1,b2,{} } = union {b1,b2}
proof end;

theorem Th2: :: MEASURE1:2
canceled;

theorem Th3: :: MEASURE1:3
canceled;

theorem Th4: :: MEASURE1:4
for b1, b2, b3, b4 being R_eal st 0. <=' b1 & 0. <=' b3 & b1 <=' b2 & b3 <=' b4 holds
b1 + b3 <=' b2 + b4
proof end;

theorem Th5: :: MEASURE1:5
for b1, b2, b3 being R_eal st 0. <=' b2 & 0. <=' b3 & b1 = b2 + b3 & b2 <' +infty holds
b3 = b1 - b2
proof end;

theorem Th6: :: MEASURE1:6
canceled;

theorem Th7: :: MEASURE1:7
for b1 being set
for b2, b3 being Subset of b1 holds {b2,b3} is Subset-Family of b1
proof end;

theorem Th8: :: MEASURE1:8
for b1 being set
for b2, b3, b4 being Subset of b1 holds {b2,b3,b4} is non empty Subset-Family of b1
proof end;

theorem Th9: :: MEASURE1:9
for b1 being set holds {{} } is Subset-Family of b1
proof end;

scheme :: MEASURE1:sch 1
s1{ F1() -> set , P1[ set ] } :
ex b1 being non empty Subset-Family of F1() st
for b2 being set holds
( b2 in b1 iff ( b2 c= F1() & P1[b2] ) )
provided
E7: ex b1 being set st
( b1 c= F1() & P1[b1] )
proof end;

notation
let c1 be set ;
let c2 be non empty Subset-Family of c1;
synonym c1 \ c2 for COMPLEMENT c2;
end;

registration
let c1 be set ;
let c2 be non empty Subset-Family of c1;
cluster a1 \ a2 -> non empty ;
coherence
not c1 \ c2 is empty
proof end;
end;

theorem Th10: :: MEASURE1:10
canceled;

theorem Th11: :: MEASURE1:11
canceled;

theorem Th12: :: MEASURE1:12
canceled;

theorem Th13: :: MEASURE1:13
canceled;

theorem Th14: :: MEASURE1:14
canceled;

theorem Th15: :: MEASURE1:15
for b1 being set
for b2 being non empty Subset-Family of b1 holds
( meet b2 = b1 \ (union (b1 \ b2)) & union b2 = b1 \ (meet (b1 \ b2)) )
proof end;

definition
let c1 be set ;
let c2 be Subset-Family of c1;
canceled;
canceled;
redefine attr a2 is compl-closed means :Def3: :: MEASURE1:def 3
for b1 being set st b1 in a2 holds
a1 \ b1 in a2;
compatibility
( c2 is compl-closed iff for b1 being set st b1 in c2 holds
c1 \ b1 in c2 )
proof end;
end;

:: deftheorem Def1 MEASURE1:def 1 :
canceled;

:: deftheorem Def2 MEASURE1:def 2 :
canceled;

:: deftheorem Def3 defines compl-closed MEASURE1:def 3 :
for b1 being set
for b2 being Subset-Family of b1 holds
( b2 is compl-closed iff for b3 being set st b3 in b2 holds
b1 \ b3 in b2 );

theorem Th16: :: MEASURE1:16
for b1 being set
for b2 being Subset-Family of b1 st b2 is cup-closed & b2 is compl-closed holds
b2 is cap-closed
proof end;

registration
let c1 be set ;
cluster cup-closed compl-closed -> cap-closed Element of bool (bool a1);
coherence
for b1 being Subset-Family of c1 st b1 is cup-closed & b1 is compl-closed holds
b1 is cap-closed
by Th16;
cluster cap-closed compl-closed -> cup-closed Element of bool (bool a1);
coherence
for b1 being Subset-Family of c1 st b1 is cap-closed & b1 is compl-closed holds
b1 is cup-closed
proof end;
end;

theorem Th17: :: MEASURE1:17
for b1 being set
for b2 being Field_Subset of b1 holds b2 = b1 \ b2
proof end;

theorem Th18: :: MEASURE1:18
for b1, b2 being set holds
( b2 is Field_Subset of b1 iff ex b3 being non empty Subset-Family of b1 st
( b2 = b3 & ( for b4 being set st b4 in b3 holds
( b1 \ b4 in b3 & ( for b5, b6 being set st b5 in b3 & b6 in b3 holds
b5 \/ b6 in b3 ) ) ) ) )
proof end;

theorem Th19: :: MEASURE1:19
for b1 being set
for b2 being non empty Subset-Family of b1 holds
( b2 is Field_Subset of b1 iff for b3 being set st b3 in b2 holds
( b1 \ b3 in b2 & ( for b4, b5 being set st b4 in b2 & b5 in b2 holds
b4 /\ b5 in b2 ) ) )
proof end;

theorem Th20: :: MEASURE1:20
for b1 being set
for b2 being Field_Subset of b1
for b3, b4 being set st b3 in b2 & b4 in b2 holds
b3 \ b4 in b2
proof end;

theorem Th21: :: MEASURE1:21
for b1 being set
for b2 being Field_Subset of b1 holds
( {} in b2 & b1 in b2 ) by PROB_1:10, PROB_1:11;

definition
let c1 be non empty set ;
let c2 be Function of c1, ExtREAL ;
let c3 be Element of c1;
redefine func . as c2 . c3 -> R_eal;
coherence
c2 . c3 is R_eal
by FUNCT_2:7;
end;

definition
let c1 be non empty set ;
let c2 be Function of c1, ExtREAL ;
redefine attr a2 is nonnegative means :Def4: :: MEASURE1:def 4
for b1 being Element of a1 holds 0. <=' a2 . b1;
compatibility
( c2 is nonnegative iff for b1 being Element of c1 holds 0. <=' c2 . b1 )
by SUPINF_2:58;
end;

:: deftheorem Def4 defines nonnegative MEASURE1:def 4 :
for b1 being non empty set
for b2 being Function of b1, ExtREAL holds
( b2 is nonnegative iff for b3 being Element of b1 holds 0. <=' b2 . b3 );

theorem Th22: :: MEASURE1:22
canceled;

theorem Th23: :: MEASURE1:23
for b1 being set
for b2 being Field_Subset of b1 ex b3 being Function of b2, ExtREAL st
( b3 is nonnegative & b3 . {} = 0. & ( for b4, b5 being Element of b2 st b4 misses b5 holds
b3 . (b4 \/ b5) = (b3 . b4) + (b3 . b5) ) )
proof end;

definition
let c1 be set ;
let c2 be Field_Subset of c1;
mode Measure of c2 -> Function of a2, ExtREAL means :Def5: :: MEASURE1:def 5
( a3 is nonnegative & a3 . {} = 0. & ( for b1, b2 being Element of a2 st b1 misses b2 holds
a3 . (b1 \/ b2) = (a3 . b1) + (a3 . b2) ) );
existence
ex b1 being Function of c2, ExtREAL st
( b1 is nonnegative & b1 . {} = 0. & ( for b2, b3 being Element of c2 st b2 misses b3 holds
b1 . (b2 \/ b3) = (b1 . b2) + (b1 . b3) ) )
by Th23;
end;

:: deftheorem Def5 defines Measure MEASURE1:def 5 :
for b1 being set
for b2 being Field_Subset of b1
for b3 being Function of b2, ExtREAL holds
( b3 is Measure of b2 iff ( b3 is nonnegative & b3 . {} = 0. & ( for b4, b5 being Element of b2 st b4 misses b5 holds
b3 . (b4 \/ b5) = (b3 . b4) + (b3 . b5) ) ) );

theorem Th24: :: MEASURE1:24
canceled;

theorem Th25: :: MEASURE1:25
for b1 being set
for b2 being Field_Subset of b1
for b3 being Measure of b2
for b4, b5 being Element of b2 st b4 c= b5 holds
b3 . b4 <=' b3 . b5
proof end;

theorem Th26: :: MEASURE1:26
for b1 being set
for b2 being Field_Subset of b1
for b3 being Measure of b2
for b4, b5 being Element of b2 st b4 c= b5 & b3 . b4 <' +infty holds
b3 . (b5 \ b4) = (b3 . b5) - (b3 . b4)
proof end;

registration
let c1 be set ;
cluster non empty cup-closed cap-closed compl-closed Element of bool (bool a1);
existence
ex b1 being Subset-Family of c1 st
( not b1 is empty & b1 is compl-closed & b1 is cap-closed )
proof end;
end;

definition
let c1 be set ;
let c2 be non empty cup-closed Subset-Family of c1;
let c3, c4 be Element of c2;
redefine func \/ as c3 \/ c4 -> Element of a2;
coherence
c3 \/ c4 is Element of c2
by FINSUB_1:def 1;
end;

definition
let c1 be set ;
let c2 be Field_Subset of c1;
let c3, c4 be Element of c2;
redefine func /\ as c3 /\ c4 -> Element of a2;
coherence
c3 /\ c4 is Element of c2
by Th19;
redefine func \ as c3 \ c4 -> Element of a2;
coherence
c3 \ c4 is Element of c2
by Th20;
end;

theorem Th27: :: MEASURE1:27
for b1 being set
for b2 being Field_Subset of b1
for b3 being Measure of b2
for b4, b5 being Element of b2 holds b3 . (b4 \/ b5) <=' (b3 . b4) + (b3 . b5)
proof end;

definition
let c1 be set ;
let c2 be Field_Subset of c1;
let c3 be Measure of c2;
let c4 be set ;
pred c4 is_measurable c3 means :Def6: :: MEASURE1:def 6
a4 in a2;
end;

:: deftheorem Def6 defines is_measurable MEASURE1:def 6 :
for b1 being set
for b2 being Field_Subset of b1
for b3 being Measure of b2
for b4 being set holds
( b4 is_measurable b3 iff b4 in b2 );

theorem Th28: :: MEASURE1:28
canceled;

theorem Th29: :: MEASURE1:29
for b1 being set
for b2 being Field_Subset of b1
for b3 being Measure of b2 holds
( {} is_measurable b3 & b1 is_measurable b3 & ( for b4, b5 being set st b4 is_measurable b3 & b5 is_measurable b3 holds
( b1 \ b4 is_measurable b3 & b4 \/ b5 is_measurable b3 & b4 /\ b5 is_measurable b3 ) ) )
proof end;

definition
let c1 be set ;
let c2 be Field_Subset of c1;
let c3 be Measure of c2;
mode measure_zero of c3 -> Element of a2 means :Def7: :: MEASURE1:def 7
a3 . a4 = 0. ;
existence
ex b1 being Element of c2 st c3 . b1 = 0.
proof end;
end;

:: deftheorem Def7 defines measure_zero MEASURE1:def 7 :
for b1 being set
for b2 being Field_Subset of b1
for b3 being Measure of b2
for b4 being Element of b2 holds
( b4 is measure_zero of b3 iff b3 . b4 = 0. );

theorem Th30: :: MEASURE1:30
canceled;

theorem Th31: :: MEASURE1:31
for b1 being set
for b2 being Field_Subset of b1
for b3 being Measure of b2
for b4 being Element of b2
for b5 being measure_zero of b3 st b4 c= b5 holds
b4 is measure_zero of b3
proof end;

theorem Th32: :: MEASURE1:32
for b1 being set
for b2 being Field_Subset of b1
for b3 being Measure of b2
for b4, b5 being measure_zero of b3 holds
( b4 \/ b5 is measure_zero of b3 & b4 /\ b5 is measure_zero of b3 & b4 \ b5 is measure_zero of b3 )
proof end;

theorem Th33: :: MEASURE1:33
for b1 being set
for b2 being Field_Subset of b1
for b3 being Measure of b2
for b4 being Element of b2
for b5 being measure_zero of b3 holds
( b3 . (b4 \/ b5) = b3 . b4 & b3 . (b4 /\ b5) = 0. & b3 . (b4 \ b5) = b3 . b4 )
proof end;

theorem Th34: :: MEASURE1:34
for b1 being set
for b2 being Subset of b1 ex b3 being Function of NAT , bool b1 st rng b3 = {b2}
proof end;

theorem Th35: :: MEASURE1:35
for b1 being set ex b2 being Function of NAT ,{b1} st
for b3 being Nat holds b2 . b3 = b1
proof end;

registration
let c1 be set ;
cluster non empty countable Element of bool (bool a1);
existence
ex b1 being Subset-Family of c1 st
( not b1 is empty & b1 is countable )
proof end;
end;

definition
let c1 be set ;
mode N_Sub_set_fam of a1 is non empty countable Subset-Family of a1;
end;

theorem Th36: :: MEASURE1:36
canceled;

theorem Th37: :: MEASURE1:37
canceled;

theorem Th38: :: MEASURE1:38
for b1 being set
for b2, b3, b4 being Subset of b1 ex b5 being Function of NAT , bool b1 st
( rng b5 = {b2,b3,b4} & b5 . 0 = b2 & b5 . 1 = b3 & ( for b6 being Nat st 1 < b6 holds
b5 . b6 = b4 ) )
proof end;

theorem Th39: :: MEASURE1:39
for b1 being set
for b2, b3 being Subset of b1 holds {b2,b3,{} } is N_Sub_set_fam of b1
proof end;

theorem Th40: :: MEASURE1:40
for b1 being set
for b2, b3 being Subset of b1 ex b4 being Function of NAT , bool b1 st
( rng b4 = {b2,b3} & b4 . 0 = b2 & ( for b5 being Nat st 0 < b5 holds
b4 . b5 = b3 ) )
proof end;

theorem Th41: :: MEASURE1:41
for b1 being set
for b2, b3 being Subset of b1 holds {b2,b3} is N_Sub_set_fam of b1
proof end;

theorem Th42: :: MEASURE1:42
for b1 being set
for b2 being N_Sub_set_fam of b1 holds b1 \ b2 is N_Sub_set_fam of b1
proof end;

definition
let c1 be set ;
let c2 be Subset-Family of c1;
canceled;
attr a2 is sigma_Field_Subset-like means :Def9: :: MEASURE1:def 9
for b1 being N_Sub_set_fam of a1 st b1 c= a2 holds
union b1 in a2;
end;

:: deftheorem Def8 MEASURE1:def 8 :
canceled;

:: deftheorem Def9 defines sigma_Field_Subset-like MEASURE1:def 9 :
for b1 being set
for b2 being Subset-Family of b1 holds
( b2 is sigma_Field_Subset-like iff for b3 being N_Sub_set_fam of b1 st b3 c= b2 holds
union b3 in b2 );

registration
let c1 be set ;
cluster non empty compl-closed sigma_Field_Subset-like Element of bool (bool a1);
existence
ex b1 being Subset-Family of c1 st
( not b1 is empty & b1 is compl-closed & b1 is sigma_Field_Subset-like )
proof end;
end;

definition
let c1 be set ;
mode sigma_Field_Subset of a1 is non empty compl-closed sigma_Field_Subset-like Subset-Family of a1;
end;

Lemma28: for b1 being set
for b2 being non empty Subset-Family of b1 st b2 is sigma_Field_Subset of b1 holds
b2 is Field_Subset of b1
proof end;

theorem Th43: :: MEASURE1:43
canceled;

theorem Th44: :: MEASURE1:44
canceled;

theorem Th45: :: MEASURE1:45
for b1 being set
for b2 being sigma_Field_Subset of b1 holds
( {} in b2 & b1 in b2 )
proof end;

registration
let c1 be set ;
cluster -> Element of bool (bool a1);
coherence
for b1 being sigma_Field_Subset of c1 holds not b1 is empty
;
end;

theorem Th46: :: MEASURE1:46
for b1 being set
for b2 being sigma_Field_Subset of b1
for b3, b4 being set st b3 in b2 & b4 in b2 holds
( b3 \/ b4 in b2 & b3 /\ b4 in b2 )
proof end;

theorem Th47: :: MEASURE1:47
for b1 being set
for b2 being sigma_Field_Subset of b1
for b3, b4 being set st b3 in b2 & b4 in b2 holds
b3 \ b4 in b2
proof end;

theorem Th48: :: MEASURE1:48
for b1 being set
for b2 being sigma_Field_Subset of b1 holds b2 = b1 \ b2
proof end;

theorem Th49: :: MEASURE1:49
for b1 being set
for b2 being non empty Subset-Family of b1 holds
( ( ( for b3 being set st b3 in b2 holds
b1 \ b3 in b2 ) & ( for b3 being N_Sub_set_fam of b1 st b3 c= b2 holds
meet b3 in b2 ) ) iff b2 is sigma_Field_Subset of b1 )
proof end;

registration
let c1 be set ;
let c2 be sigma_Field_Subset of c1;
cluster disjoint_valued M8( NAT ,a2);
existence
ex b1 being Function of NAT ,c2 st b1 is disjoint_valued
proof end;
end;

definition
let c1 be set ;
let c2 be sigma_Field_Subset of c1;
mode Sep_Sequence of a2 is disjoint_valued Function of NAT ,a2;
end;

definition
let c1 be set ;
let c2 be sigma_Field_Subset of c1;
let c3 be Function of NAT ,c2;
redefine func rng as rng c3 -> non empty Subset-Family of a1;
coherence
rng c3 is non empty Subset-Family of c1
proof end;
end;

theorem Th50: :: MEASURE1:50
canceled;

theorem Th51: :: MEASURE1:51
canceled;

theorem Th52: :: MEASURE1:52
for b1 being set
for b2 being sigma_Field_Subset of b1
for b3 being Function of NAT ,b2 holds rng b3 is N_Sub_set_fam of b1
proof end;

theorem Th53: :: MEASURE1:53
for b1 being set
for b2 being sigma_Field_Subset of b1
for b3 being Function of NAT ,b2 holds union (rng b3) is Element of b2
proof end;

theorem Th54: :: MEASURE1:54
for b1, b2 being non empty set
for b3 being Function of b1,b2
for b4 being Function of b2, ExtREAL st b4 is nonnegative holds
b4 * b3 is nonnegative
proof end;

theorem Th55: :: MEASURE1:55
for b1 being set
for b2 being sigma_Field_Subset of b1
for b3, b4 being R_eal ex b5 being Function of b2, ExtREAL st
for b6 being Element of b2 holds
( ( b6 = {} implies b5 . b6 = b3 ) & ( b6 <> {} implies b5 . b6 = b4 ) )
proof end;

theorem Th56: :: MEASURE1:56
for b1 being set
for b2 being sigma_Field_Subset of b1 ex b3 being Function of b2, ExtREAL st
for b4 being Element of b2 holds
( ( b4 = {} implies b3 . b4 = 0. ) & ( b4 <> {} implies b3 . b4 = +infty ) ) by Th55;

theorem Th57: :: MEASURE1:57
for b1 being set
for b2 being sigma_Field_Subset of b1 ex b3 being Function of b2, ExtREAL st
for b4 being Element of b2 holds b3 . b4 = 0.
proof end;

theorem Th58: :: MEASURE1:58
for b1 being set
for b2 being sigma_Field_Subset of b1 ex b3 being Function of b2, ExtREAL st
( b3 is nonnegative & b3 . {} = 0. & ( for b4 being Sep_Sequence of b2 holds SUM (b3 * b4) = b3 . (union (rng b4)) ) )
proof end;

definition
let c1 be set ;
let c2 be sigma_Field_Subset of c1;
canceled;
mode sigma_Measure of c2 -> Function of a2, ExtREAL means :Def11: :: MEASURE1:def 11
( a3 is nonnegative & a3 . {} = 0. & ( for b1 being Sep_Sequence of a2 holds SUM (a3 * b1) = a3 . (union (rng b1)) ) );
existence
ex b1 being Function of c2, ExtREAL st
( b1 is nonnegative & b1 . {} = 0. & ( for b2 being Sep_Sequence of c2 holds SUM (b1 * b2) = b1 . (union (rng b2)) ) )
by Th58;
end;

:: deftheorem Def10 MEASURE1:def 10 :
canceled;

:: deftheorem Def11 defines sigma_Measure MEASURE1:def 11 :
for b1 being set
for b2 being sigma_Field_Subset of b1
for b3 being Function of b2, ExtREAL holds
( b3 is sigma_Measure of b2 iff ( b3 is nonnegative & b3 . {} = 0. & ( for b4 being Sep_Sequence of b2 holds SUM (b3 * b4) = b3 . (union (rng b4)) ) ) );

registration
let c1 be set ;
cluster non empty compl-closed sigma_Field_Subset-like -> non empty cup-closed Element of bool (bool a1);
coherence
for b1 being non empty Subset-Family of c1 st b1 is sigma_Field_Subset-like & b1 is compl-closed holds
b1 is cup-closed
by Lemma28;
end;

theorem Th59: :: MEASURE1:59
canceled;

theorem Th60: :: MEASURE1:60
for b1 being set
for b2 being sigma_Field_Subset of b1
for b3 being sigma_Measure of b2 holds b3 is Measure of b2
proof end;

theorem Th61: :: MEASURE1:61
for b1 being set
for b2 being sigma_Field_Subset of b1
for b3 being sigma_Measure of b2
for b4, b5 being Element of b2 st b4 misses b5 holds
b3 . (b4 \/ b5) = (b3 . b4) + (b3 . b5)
proof end;

theorem Th62: :: MEASURE1:62
for b1 being set
for b2 being sigma_Field_Subset of b1
for b3 being sigma_Measure of b2
for b4, b5 being Element of b2 st b4 c= b5 holds
b3 . b4 <=' b3 . b5
proof end;

theorem Th63: :: MEASURE1:63
for b1 being set
for b2 being sigma_Field_Subset of b1
for b3 being sigma_Measure of b2
for b4, b5 being Element of b2 st b4 c= b5 & b3 . b4 <' +infty holds
b3 . (b5 \ b4) = (b3 . b5) - (b3 . b4)
proof end;

theorem Th64: :: MEASURE1:64
for b1 being set
for b2 being sigma_Field_Subset of b1
for b3 being sigma_Measure of b2
for b4, b5 being Element of b2 holds b3 . (b4 \/ b5) <=' (b3 . b4) + (b3 . b5)
proof end;

definition
let c1 be set ;
let c2 be sigma_Field_Subset of c1;
let c3 be sigma_Measure of c2;
let c4 be set ;
pred c4 is_measurable c3 means :Def12: :: MEASURE1:def 12
a4 in a2;
end;

:: deftheorem Def12 defines is_measurable MEASURE1:def 12 :
for b1 being set
for b2 being sigma_Field_Subset of b1
for b3 being sigma_Measure of b2
for b4 being set holds
( b4 is_measurable b3 iff b4 in b2 );

theorem Th65: :: MEASURE1:65
canceled;

theorem Th66: :: MEASURE1:66
for b1 being set
for b2 being sigma_Field_Subset of b1
for b3 being sigma_Measure of b2 holds
( {} is_measurable b3 & b1 is_measurable b3 & ( for b4, b5 being set st b4 is_measurable b3 & b5 is_measurable b3 holds
( b1 \ b4 is_measurable b3 & b4 \/ b5 is_measurable b3 & b4 /\ b5 is_measurable b3 ) ) )
proof end;

theorem Th67: :: MEASURE1:67
for b1 being set
for b2 being sigma_Field_Subset of b1
for b3 being sigma_Measure of b2
for b4 being N_Sub_set_fam of b1 st ( for b5 being set st b5 in b4 holds
b5 is_measurable b3 ) holds
( union b4 is_measurable b3 & meet b4 is_measurable b3 )
proof end;

definition
let c1 be set ;
let c2 be sigma_Field_Subset of c1;
let c3 be sigma_Measure of c2;
mode measure_zero of c3 -> Element of a2 means :Def13: :: MEASURE1:def 13
a3 . a4 = 0. ;
existence
ex b1 being Element of c2 st c3 . b1 = 0.
proof end;
end;

:: deftheorem Def13 defines measure_zero MEASURE1:def 13 :
for b1 being set
for b2 being sigma_Field_Subset of b1
for b3 being sigma_Measure of b2
for b4 being Element of b2 holds
( b4 is measure_zero of b3 iff b3 . b4 = 0. );

theorem Th68: :: MEASURE1:68
canceled;

theorem Th69: :: MEASURE1:69
for b1 being set
for b2 being sigma_Field_Subset of b1
for b3 being sigma_Measure of b2
for b4 being Element of b2
for b5 being measure_zero of b3 st b4 c= b5 holds
b4 is measure_zero of b3
proof end;

theorem Th70: :: MEASURE1:70
for b1 being set
for b2 being sigma_Field_Subset of b1
for b3 being sigma_Measure of b2
for b4, b5 being measure_zero of b3 holds
( b4 \/ b5 is measure_zero of b3 & b4 /\ b5 is measure_zero of b3 & b4 \ b5 is measure_zero of b3 )
proof end;

theorem Th71: :: MEASURE1:71
for b1 being set
for b2 being sigma_Field_Subset of b1
for b3 being sigma_Measure of b2
for b4 being Element of b2
for b5 being measure_zero of b3 holds
( b3 . (b4 \/ b5) = b3 . b4 & b3 . (b4 /\ b5) = 0. & b3 . (b4 \ b5) = b3 . b4 )
proof end;