:: Some Properties of Binary Relations
:: by Waldemar Korczy\'nski
::
:: Received January 17, 1992
:: Copyright (c) 1992-2021 Association of Mizar Users


Lm1: for X, Y being set st X <> {} & Y <> {} holds
( dom [:X,Y:] = X & rng [:X,Y:] = Y )
by RELAT_1:160;

theorem Th1: :: SYSREL:1
for X, Y being set
for R being Relation holds
( dom (R /\ [:X,Y:]) c= X & rng (R /\ [:X,Y:]) c= Y )
proof end;

theorem :: SYSREL:2
for X, Y being set
for R being Relation st X misses Y holds
dom (R /\ [:X,Y:]) misses rng (R /\ [:X,Y:])
proof end;

theorem Th3: :: SYSREL:3
for X, Y being set
for R being Relation st R c= [:X,Y:] holds
( dom R c= X & rng R c= Y )
proof end;

theorem :: SYSREL:4
for X, Y being set
for R being Relation st R c= [:X,Y:] holds
R ~ c= [:Y,X:]
proof end;

theorem :: SYSREL:5
for X, Y being set holds [:X,Y:] ~ = [:Y,X:]
proof end;

theorem Th6: :: SYSREL:6
for R, S, T being Relation holds (R \/ S) * T = (R * T) \/ (S * T)
proof end;

theorem :: SYSREL:7
for x, y being object
for X, Y being set
for R being Relation holds
( ( X misses Y & R c= [:X,Y:] \/ [:Y,X:] & [x,y] in R & x in X implies ( not x in Y & not y in X & y in Y ) ) & ( X misses Y & R c= [:X,Y:] \/ [:Y,X:] & [x,y] in R & y in Y implies ( not y in X & not x in Y & x in X ) ) & ( X misses Y & R c= [:X,Y:] \/ [:Y,X:] & [x,y] in R & x in Y implies ( not x in X & not y in Y & y in X ) ) & ( X misses Y & R c= [:X,Y:] \/ [:Y,X:] & [x,y] in R & y in X implies ( not x in X & not y in Y & x in Y ) ) )
proof end;

theorem Th8: :: SYSREL:8
for X, Y, Z being set
for R being Relation st R c= [:X,Y:] holds
( R | Z = R /\ [:Z,Y:] & Z |` R = R /\ [:X,Z:] )
proof end;

theorem :: SYSREL:9
for X, Y, Z, W being set
for R being Relation st R c= [:X,Y:] & X = Z \/ W holds
R = (R | Z) \/ (R | W)
proof end;

theorem :: SYSREL:10
for X, Y being set
for R being Relation st X misses Y & R c= [:X,Y:] \/ [:Y,X:] holds
R | X c= [:X,Y:]
proof end;

theorem :: SYSREL:11
for R, S being Relation st R c= S holds
R ~ c= S ~
proof end;

Lm2: for X being set holds id X c= [:X,X:]
proof end;

theorem Th12: :: SYSREL:12
for X being set holds (id X) * (id X) = id X
proof end;

theorem :: SYSREL:13
for x being object holds id {x} = {[x,x]}
proof end;

theorem Th14: :: SYSREL:14
for X, Y being set holds
( id (X \/ Y) = (id X) \/ (id Y) & id (X /\ Y) = (id X) /\ (id Y) & id (X \ Y) = (id X) \ (id Y) )
proof end;

theorem Th15: :: SYSREL:15
for X, Y being set st X c= Y holds
id X c= id Y
proof end;

theorem :: SYSREL:16
for X, Y being set holds (id (X \ Y)) \ (id X) = {} by Th15, XBOOLE_1:37;

theorem :: SYSREL:17
for R being Relation st R c= id (dom R) holds
R = id (dom R)
proof end;

theorem :: SYSREL:18
for X being set
for R being Relation st id X c= R \/ (R ~) holds
( id X c= R & id X c= R ~ )
proof end;

theorem :: SYSREL:19
for X being set
for R being Relation st id X c= R holds
id X c= R ~
proof end;

:: CLOSURE RELATION
theorem :: SYSREL:20
for X being set
for R being Relation st R c= [:X,X:] holds
( R \ (id (dom R)) = R \ (id X) & R \ (id (rng R)) = R \ (id X) )
proof end;

theorem :: SYSREL:21
for X being set
for R being Relation holds
( ( (id X) * (R \ (id X)) = {} implies dom (R \ (id X)) = (dom R) \ X ) & ( (R \ (id X)) * (id X) = {} implies rng (R \ (id X)) = (rng R) \ X ) )
proof end;

theorem Th22: :: SYSREL:22
for R being Relation holds
( ( R c= R * R & R * (R \ (id (rng R))) = {} implies id (rng R) c= R ) & ( R c= R * R & (R \ (id (dom R))) * R = {} implies id (dom R) c= R ) )
proof end;

theorem :: SYSREL:23
for R being Relation holds
( ( R c= R * R & R * (R \ (id (rng R))) = {} implies R /\ (id (rng R)) = id (rng R) ) & ( R c= R * R & (R \ (id (dom R))) * R = {} implies R /\ (id (dom R)) = id (dom R) ) ) by Th22, XBOOLE_1:28;

theorem :: SYSREL:24
for X being set
for R being Relation holds
( ( R * (R \ (id X)) = {} implies R * (R \ (id (rng R))) = {} ) & ( (R \ (id X)) * R = {} implies (R \ (id (dom R))) * R = {} ) )
proof end;

:: OPERATION CL
definition
let R be Relation;
func CL R -> Relation equals :: SYSREL:def 1
R /\ (id (dom R));
correctness
coherence
R /\ (id (dom R)) is Relation;
;
end;

:: deftheorem defines CL SYSREL:def 1 :
for R being Relation holds CL R = R /\ (id (dom R));

theorem Th25: :: SYSREL:25
for R being Relation
for x, y being object st [x,y] in CL R holds
( x in dom (CL R) & x = y )
proof end;

theorem Th26: :: SYSREL:26
for R being Relation holds dom (CL R) = rng (CL R)
proof end;

theorem Th27: :: SYSREL:27
for x being object
for R being Relation holds
( ( x in dom (CL R) implies ( x in dom R & [x,x] in R ) ) & ( x in dom R & [x,x] in R implies x in dom (CL R) ) & ( x in rng (CL R) implies ( x in dom R & [x,x] in R ) ) & ( x in dom R & [x,x] in R implies x in rng (CL R) ) & ( x in rng (CL R) implies ( x in rng R & [x,x] in R ) ) & ( x in rng R & [x,x] in R implies x in rng (CL R) ) & ( x in dom (CL R) implies ( x in rng R & [x,x] in R ) ) & ( x in rng R & [x,x] in R implies x in dom (CL R) ) )
proof end;

theorem Th28: :: SYSREL:28
for R being Relation holds CL R = id (dom (CL R))
proof end;

theorem Th29: :: SYSREL:29
for x, y being object
for R being Relation holds
( ( R * R = R & R * (R \ (CL R)) = {} & [x,y] in R & x <> y implies ( x in (dom R) \ (dom (CL R)) & y in dom (CL R) ) ) & ( R * R = R & (R \ (CL R)) * R = {} & [x,y] in R & x <> y implies ( y in (rng R) \ (dom (CL R)) & x in dom (CL R) ) ) )
proof end;

theorem :: SYSREL:30
for x, y being object
for R being Relation holds
( ( R * R = R & R * (R \ (id (dom R))) = {} & [x,y] in R & x <> y implies ( x in (dom R) \ (dom (CL R)) & y in dom (CL R) ) ) & ( R * R = R & (R \ (id (dom R))) * R = {} & [x,y] in R & x <> y implies ( y in (rng R) \ (dom (CL R)) & x in dom (CL R) ) ) )
proof end;

theorem :: SYSREL:31
for R being Relation holds
( ( R * R = R & R * (R \ (id (dom R))) = {} implies ( dom (CL R) = rng R & rng (CL R) = rng R ) ) & ( R * R = R & (R \ (id (dom R))) * R = {} implies ( dom (CL R) = dom R & rng (CL R) = dom R ) ) )
proof end;

theorem Th32: :: SYSREL:32
for R being Relation holds
( dom (CL R) c= dom R & rng (CL R) c= rng R & rng (CL R) c= dom R & dom (CL R) c= rng R )
proof end;

theorem :: SYSREL:33
for R being Relation holds
( id (dom (CL R)) c= id (dom R) & id (rng (CL R)) c= id (dom R) ) by Th15, Th32;

theorem Th34: :: SYSREL:34
for R being Relation holds
( id (dom (CL R)) c= R & id (rng (CL R)) c= R )
proof end;

theorem Th35: :: SYSREL:35
for X being set
for R being Relation holds
( ( id X c= R & (id X) * (R \ (id X)) = {} implies R | X = id X ) & ( id X c= R & (R \ (id X)) * (id X) = {} implies X |` R = id X ) )
proof end;

theorem :: SYSREL:36
for R being Relation holds
( ( (id (dom (CL R))) * (R \ (id (dom (CL R)))) = {} implies ( R | (dom (CL R)) = id (dom (CL R)) & R | (rng (CL R)) = id (dom (CL R)) ) ) & ( (R \ (id (rng (CL R)))) * (id (rng (CL R))) = {} implies ( (dom (CL R)) |` R = id (dom (CL R)) & (rng (CL R)) |` R = id (rng (CL R)) ) ) )
proof end;

theorem :: SYSREL:37
for R being Relation holds
( ( R * (R \ (id (dom R))) = {} implies (id (dom (CL R))) * (R \ (id (dom (CL R)))) = {} ) & ( (R \ (id (dom R))) * R = {} implies (R \ (id (dom (CL R)))) * (id (dom (CL R))) = {} ) )
proof end;

theorem Th38: :: SYSREL:38
for R, S being Relation holds
( ( S * R = S & R * (R \ (id (dom R))) = {} implies S * (R \ (id (dom R))) = {} ) & ( R * S = S & (R \ (id (dom R))) * R = {} implies (R \ (id (dom R))) * S = {} ) )
proof end;

theorem Th39: :: SYSREL:39
for R, S being Relation holds
( ( S * R = S & R * (R \ (id (dom R))) = {} implies CL S c= CL R ) & ( R * S = S & (R \ (id (dom R))) * R = {} implies CL S c= CL R ) )
proof end;

theorem :: SYSREL:40
for R, S being Relation holds
( ( S * R = S & R * (R \ (id (dom R))) = {} & R * S = R & S * (S \ (id (dom S))) = {} implies CL S = CL R ) & ( R * S = S & (R \ (id (dom R))) * R = {} & S * R = R & (S \ (id (dom S))) * S = {} implies CL S = CL R ) ) by Th39;