:: Products in Categories without Uniqueness of { \bf cod } and { \bf dom
:: }
:: by Artur Korni{\l}owicz
::
:: Received August 19, 2012
:: Copyright (c) 2012 Association of Mizar Users
:: (Stowarzyszenie Uzytkownikow Mizara, Bialystok, Poland).
:: This code can be distributed under the GNU General Public Licence
:: version 3.0 or later, or the Creative Commons Attribution-ShareAlike
:: License version 3.0 or later, subject to the binding interpretation
:: detailed in file COPYING.interpretation.
:: See COPYING.GPL and COPYING.CC-BY-SA for the full text of these
:: licenses, or see http://www.gnu.org/licenses/gpl.html and
:: http://creativecommons.org/licenses/by-sa/3.0/.
environ
vocabularies ALTCAT_1, CAT_1, RELAT_1, ALTCAT_3, CAT_3, FUNCT_1, PBOOLE,
ALTCAT_5, FUNCOP_1, CARD_1, FUNCT_2, XBOOLE_0, SUBSET_1, STRUCT_0,
TARSKI, PARTFUN1, CARD_3, MSUALG_6;
notations TARSKI, XBOOLE_0, SUBSET_1, RELAT_1, FUNCT_1, RELSET_1, PARTFUN1,
FUNCT_2, PBOOLE, CARD_3, FUNCOP_1, NUMBERS, STRUCT_0, ALTCAT_1, ALTCAT_3;
constructors ALTCAT_3, RELSET_1, CARD_3, NUMBERS;
registrations XBOOLE_0, RELSET_1, FUNCOP_1, STRUCT_0, ALTCAT_1, FUNCT_2,
FUNCT_1, CARD_3, RELAT_1;
requirements SUBSET, BOOLE;
definitions TARSKI, RELAT_1, FUNCOP_1, PARTFUN1, ALTCAT_1, ALTCAT_3;
theorems FUNCT_2, FUNCOP_1, CARD_1, TARSKI, ALTCAT_1, FUNCT_5, FUNCT_1,
ALTCAT_3, PARTFUN1, YELLOW17, RELAT_1, CARD_3, PBOOLE;
schemes PBOOLE, CLASSES1;
begin
reserve
I for set,
E for non empty set;
registration
cluster empty -> {}-defined for Relation;
coherence
proof
let R be Relation;
assume R is empty;
hence dom R c= {};
end;
end;
definition
let C be AltGraph;
attr C is functional means
:Def2:
for a, b being object of C holds <^a,b^> is functional;
end;
registration
let E;
cluster EnsCat E -> functional;
coherence
proof
let a, b be object of EnsCat E;
<^a,b^> = Funcs(a,b) by ALTCAT_1:def 14;
hence thesis;
end;
end;
registration
cluster functional strict for category;
existence
proof
take EnsCat 1;
thus thesis;
end;
end;
registration
let C be functional AltCatStr;
cluster the AltGraph of C -> functional;
coherence
proof
let a,b be object of the AltGraph of C;
reconsider a1 = a, b1 = b as object of C;
<^a1,b1^> is functional by Def2;
hence thesis;
end;
end;
registration
cluster functional strict for AltGraph;
existence
proof
take the AltGraph of EnsCat 1;
thus thesis;
end;
end;
registration
cluster functional strict for category;
existence
proof
take EnsCat 1;
thus thesis;
end;
end;
registration
let C be functional AltGraph;
let a,b be object of C;
cluster <^a,b^> -> functional;
coherence by Def2;
end;
reconsider a = 0, b = 1 as Element of 2 by CARD_1:50,TARSKI:def 2;
set C = EnsCat 1;
Lm1: the carrier of C = 1 by ALTCAT_1:def 14;
reconsider o = {} as object of C by Lm1,CARD_1:49,TARSKI:def 1;
Lm2: Funcs({} qua set,{} qua set) = {{}} by FUNCT_5:57;
Lm3:
now
let o1,o be object of C;
A1: o1 = {} & o = {} by Lm1,CARD_1:49,TARSKI:def 1;
<^o1,o^> = Funcs(o1,o) by ALTCAT_1:def 14;
hence {} is Morphism of o1,o & {} in <^o1,o^> by A1,Lm1,Lm2,CARD_1:49;
end;
Lm4:
now
let o1, o be object of C;
let m1 be Morphism of o1,o;
A1: o = {} & o1 = {} by Lm1,CARD_1:49,TARSKI:def 1;
<^o1,o^> = Funcs(o1,o) by ALTCAT_1:def 14;
hence m1 = {} by A1,Lm2,TARSKI:def 1;
end;
Lm5:
now
let o1,o be object of C;
o = {} & o1 = {} by Lm1,CARD_1:49,TARSKI:def 1;
hence o1 = o;
end;
Lm6:
now
let o1,o be object of C;
let m1,m be Morphism of o1,o;
thus m1 = {} by Lm4
.= m by Lm4;
end;
definition
let C be non empty AltCatStr;
let I be set;
mode ObjectsFamily of I,C is Function of I,C;
end;
definition
let C be non empty AltCatStr;
let o be object of C;
let I be set;
let f be ObjectsFamily of I,C;
mode MorphismsFamily of o,f -> ManySortedSet of I means
:Def3:
for i being set st i in I
ex o1 being object of C st o1 = f.i & it.i is Morphism of o,o1;
existence
proof
defpred P[set,set] means ex o1 being object of C st o1 = f.$1 &
$2 is Morphism of o,o1;
A1: for i being set st i in I ex j being set st P[i,j]
proof
let i be set;
assume i in I;
then reconsider o1 = f.i as object of C by FUNCT_2:5;
take the Morphism of o,o1;
thus thesis;
end;
ex f being ManySortedSet of I st
for i being set st i in I holds P[i,f.i] from PBOOLE:sch 3(A1);
hence thesis;
end;
end;
definition
let C be non empty AltCatStr;
let o be object of C;
let I be non empty set;
let f be ObjectsFamily of I,C;
redefine mode MorphismsFamily of o,f means
:Def4:
for i being Element of I holds it.i is Morphism of o,f.i;
compatibility
proof
let F be ManySortedSet of I;
hereby
assume
A1: F is MorphismsFamily of o,f;
let i be Element of I;
ex o1 being object of C st o1 = f.i & F.i is Morphism of o,o1
by A1,Def3;
hence F.i is Morphism of o,f.i;
end;
assume
A2: for i being Element of I holds F.i is Morphism of o,f.i;
let i be set;
assume i in I;
then reconsider j = i as Element of I;
take f.j;
thus thesis by A2;
end;
end;
definition
let C be non empty AltCatStr;
let o be object of C;
let I be non empty set;
let f be ObjectsFamily of I,C;
let M be MorphismsFamily of o,f;
let i be Element of I;
redefine func M.i -> Morphism of o,f.i;
coherence by Def4;
end;
registration
let C be functional non empty AltCatStr;
let o be object of C;
let I be set;
let f be ObjectsFamily of I,C;
cluster -> Function-yielding for MorphismsFamily of o,f;
coherence
proof
let F be MorphismsFamily of o,f;
let i be set;
assume i in dom F;
then ex o1 being object of C st
o1 = f.i & F.i is Morphism of o,o1 by Def3;
hence thesis;
end;
end;
theorem Th1:
for C being non empty AltCatStr, o being object of C
for f being ObjectsFamily of {},C holds
{} is MorphismsFamily of o,f
proof
let C be non empty AltCatStr, o be object of C, f be ObjectsFamily of {},C;
reconsider A = {} as {}-defined Relation;
A is total
proof
thus dom A = {};
end;
then reconsider A = {} as ManySortedSet of {};
A is MorphismsFamily of o,f
proof
let i be set;
thus thesis;
end;
hence thesis;
end;
definition
let C be non empty AltCatStr;
let I be set;
let A be ObjectsFamily of I,C;
let B be object of C;
let P be MorphismsFamily of B,A;
attr P is feasible means :Def5:
for i being set st i in I ex o being object of C st o = A.i & P.i in <^B,o^>;
end;
definition
let C be non empty AltCatStr;
let I be non empty set;
let A be ObjectsFamily of I,C;
let B be object of C;
let P be MorphismsFamily of B,A;
redefine attr P is feasible means :Def6:
for i being Element of I holds P.i in <^B,A.i^>;
compatibility
proof
thus P is feasible implies
for i being Element of I holds P.i in <^B,A.i^>
proof
assume
A1: P is feasible;
let i be Element of I;
ex o being object of C st o = A.i & P.i in <^B,o^> by A1,Def5;
hence thesis;
end;
assume
A2: for i being Element of I holds P.i in <^B,A.i^>;
let i be set;
assume i in I;
then reconsider i as Element of I;
reconsider A as ObjectsFamily of I,C;
take A.i;
thus thesis by A2;
end;
end;
definition
let C be category;
let I be set;
let A be ObjectsFamily of I,C;
let B be object of C; :: product object
let P be MorphismsFamily of B,A; :: product family
attr P is projection-morphisms means :Def7:
for X being object of C, F being MorphismsFamily of X,A
st F is feasible
ex f being Morphism of X,B st f in <^X,B^> &
::existence
(for i being set st i in I
ex si being object of C, Pi being Morphism of B,si st
si = A.i & Pi = P.i & F.i = Pi * f) &
::uniqueness
for f1 being Morphism of X,B st for i being set st i in I
ex si being object of C, Pi being Morphism of B,si st
si = A.i & Pi = P.i & F.i = Pi * f1
holds f = f1;
end;
definition
let C be category;
let I be non empty set;
let A be ObjectsFamily of I,C;
let B be object of C;
let P be MorphismsFamily of B,A;
redefine attr P is projection-morphisms means
:Def8:
for X being object of C, F being MorphismsFamily of X,A st F is feasible
ex f being Morphism of X,B st f in <^X,B^> &
::existence
(for i being Element of I holds F.i = P.i * f) &
::uniqueness
for f1 being Morphism of X,B st
for i being Element of I holds F.i = P.i * f1
holds f = f1;
correctness
proof
thus P is projection-morphisms implies
for Y being object of C, F being MorphismsFamily of Y,A st F is feasible
ex f being Morphism of Y,B st f in <^Y,B^> &
(for i being Element of I holds F.i = P.i * f) &
for f1 being Morphism of Y,B st
for i being Element of I holds F.i = P.i * f1
holds f = f1
proof
assume
A1: P is projection-morphisms;
let Y be object of C, F be MorphismsFamily of Y,A;
assume
A2: F is feasible;
consider f being Morphism of Y,B such that
A3: f in <^Y,B^> and
A4: for i being set st i in I
ex si being object of C, Pi being Morphism of B,si st
si = A.i & Pi = P.i & F.i = Pi * f and
A5: for f1 being Morphism of Y,B st for i being set st i in I
ex si being object of C, Pi being Morphism of B,si st
si = A.i & Pi = P.i & F.i = Pi * f1
holds f = f1 by A2,A1,Def7;
take f;
thus f in <^Y,B^> by A3;
hereby
let i be Element of I;
ex si being object of C, Pi being Morphism of B,si st
si = A.i & Pi = P.i & F.i = Pi * f by A4;
hence F.i = P.i * f;
end;
let f1 be Morphism of Y,B such that
A6: for i being Element of I holds F.i = P.i * f1;
for i being set st i in I
ex si being object of C, Pi being Morphism of B,si st
si = A.i & Pi = P.i & F.i = Pi * f1
proof
let i be set;
assume i in I;
then reconsider i as Element of I;
reconsider si = A.i as object of C;
reconsider Pi = P.i as Morphism of B,si;
take si, Pi;
thus thesis by A6;
end;
hence thesis by A5;
end;
assume
A7: for Y being object of C, F being MorphismsFamily of Y,A st F is feasible
ex f being Morphism of Y,B st f in <^Y,B^> &
(for i being Element of I holds F.i = P.i * f) &
for f1 being Morphism of Y,B st
for i being Element of I holds F.i = P.i * f1
holds f = f1;
let Y be object of C, F be MorphismsFamily of Y,A;
assume F is feasible;
then consider f be Morphism of Y,B such that
A8: f in <^Y,B^> and
A9: for i being Element of I holds F.i = P.i * f and
A10: for f1 being Morphism of Y,B st
for i being Element of I holds F.i = P.i * f1
holds f = f1 by A7;
take f;
thus f in <^Y,B^> by A8;
thus for i being set st i in I
ex si being object of C, Pi being Morphism of B,si st
si = A.i & Pi = P.i & F.i = Pi * f
proof
let i be set;
assume i in I;
then reconsider j = i as Element of I;
take A.j, P.j;
thus thesis by A9;
end;
let f1 be Morphism of Y,B such that
A11: for i being set st i in I
ex si being object of C, Pi being Morphism of B,si st
si = A.i & Pi = P.i & F.i = Pi * f1;
now
let i be Element of I;
ex si being object of C, Pi being Morphism of B,si st
si = A.i & Pi = P.i & F.i = Pi * f1 by A11;
hence F.i = P.i * f1;
end;
hence thesis by A10;
end;
end;
registration
let C be category, A be ObjectsFamily of {},C;
let B be object of C;
cluster -> feasible for MorphismsFamily of B,A;
coherence
proof
let P be MorphismsFamily of B,A;
let i be set;
thus thesis;
end;
end;
theorem Th2:
for C being category, A being ObjectsFamily of {},C
for B being object of C st B is terminal holds
ex P being MorphismsFamily of B,A st P is empty projection-morphisms
proof
let C be category;
let A be ObjectsFamily of {},C;
let B be object of C;
assume
A1: B is terminal;
reconsider P = {} as MorphismsFamily of B,A by Th1;
take P;
thus P is empty;
let X be object of C, F be MorphismsFamily of X,A;
assume F is feasible;
consider f being Morphism of X,B such that
A2: f in <^X,B^> &
for M1 being Morphism of X,B st M1 in <^X,B^> holds f = M1
by A1,ALTCAT_3:27;
take f;
thus thesis by A2;
end;
theorem Th3:
for A being ObjectsFamily of I,EnsCat 1, o being object of EnsCat 1
holds I --> {} is MorphismsFamily of o,A
proof
let A be ObjectsFamily of I,C;
let o be object of C;
let i be set such that
A1: i in I;
reconsider I as non empty set by A1;
reconsider j = i as Element of I by A1;
reconsider A1 = A as ObjectsFamily of I,C;
reconsider o1 = A1.j as object of C;
take o1;
thus o1 = A.i;
(I-->{}).j = {} by FUNCOP_1:7;
hence thesis by Lm3;
end;
theorem Th4:
for A being ObjectsFamily of I,EnsCat 1,
o being object of EnsCat 1,
P being MorphismsFamily of o,A st P = I --> {} holds
P is feasible projection-morphisms
proof
let A be ObjectsFamily of I,EnsCat 1;
let o be object of EnsCat 1;
let P be MorphismsFamily of o,A;
assume
A1: P = I --> {};
thus P is feasible
proof
let i be set;
assume
A2: i in I;
then reconsider I as non empty set;
reconsider i as Element of I by A2;
reconsider A as ObjectsFamily of I,C;
P.i = {} by A1,FUNCOP_1:7;
then P.i in <^o,A.i^> by Lm3;
hence thesis;
end;
let Y be object of C, F being MorphismsFamily of Y,A;
assume F is feasible;
reconsider f = {} as Morphism of Y,o by Lm3;
take f;
thus f in <^Y,o^> by Lm3;
thus for i being set st i in I
ex si being object of C, Pi being Morphism of o,si st
si = A.i & Pi = P.i & F.i = Pi * f
proof
let i be set;
assume
A3: i in I;
then reconsider I as non empty set;
reconsider j = i as Element of I by A3;
reconsider M = {} as Morphism of o,o by Lm3;
reconsider A1 = A as ObjectsFamily of I,C;
reconsider F1 = F as MorphismsFamily of Y,A1;
take o, M;
A1.j = {} by Lm1,CARD_1:49,TARSKI:def 1;
hence o = A.i by Lm5;
thus M = P.i by A1,A3,FUNCOP_1:7;
F1.j is Morphism of Y,o & M*f is Morphism of Y,o by Lm5;
hence thesis by Lm6;
end;
thus thesis by Lm4;
end;
definition
let C be category;
attr C is with_products means
:Def9:
for I being set, A being ObjectsFamily of I,C
ex B being object of C, P being MorphismsFamily of B,A st
P is feasible projection-morphisms;
end;
registration
cluster EnsCat 1 -> with_products;
coherence
proof
let I be set, A be ObjectsFamily of I,C;
reconsider P = I --> {} as MorphismsFamily of o,A by Th3;
take o,P;
thus thesis by Th4;
end;
end;
registration
cluster with_products for category;
existence
proof
take EnsCat 1;
thus thesis;
end;
end;
definition
let C be category;
let I be set, A be ObjectsFamily of I,C;
let B be object of C;
attr B is A-CatProduct-like means
:Def10:
ex P being MorphismsFamily of B,A st P is feasible projection-morphisms;
end;
registration
let C be with_products category;
let I be set, A be ObjectsFamily of I,C;
cluster A-CatProduct-like for object of C;
existence
proof
consider B being object of C, P being MorphismsFamily of B,A such that
A1: P is feasible projection-morphisms by Def9;
take B,P;
thus thesis by A1;
end;
end;
registration
let C be category;
let A be ObjectsFamily of {},C;
cluster A-CatProduct-like -> terminal for object of C;
coherence
proof
let B be object of C such that
A1: B is A-CatProduct-like;
for X being object of C
ex M being Morphism of X,B st M in <^X,B^> &
for M1 being Morphism of X,B st M1 in <^X,B^> holds M = M1
proof
let X be object of C;
consider P being MorphismsFamily of B,A such that
A2: P is feasible projection-morphisms by A1,Def10;
set F = the MorphismsFamily of X,A;
consider f being Morphism of X,B such that
A3: f in <^X,B^> and
for i being set st i in {}
ex si being object of C, Pi being Morphism of B,si st
si = A.i & Pi = P.i & F.i = Pi * f and
A4: for f1 being Morphism of X,B st for i being set st i in {}
ex si being object of C, Pi being Morphism of B,si st
si = A.i & Pi = P.i & F.i = Pi * f1
holds f = f1 by A2,Def7;
take f;
thus f in <^X,B^> by A3;
let M be Morphism of X,B;
for i being set st i in {}
ex si being object of C, Pi being Morphism of B,si st
si = A.i & Pi = P.i & F.i = Pi * M;
hence thesis by A4;
end;
hence thesis by ALTCAT_3:27;
end;
end;
theorem
for C being category, A being ObjectsFamily of {},C
for B being object of C st B is terminal holds
B is A-CatProduct-like
proof
let C be category;
let A be ObjectsFamily of {},C;
let B be object of C;
assume B is terminal;
then ex P being MorphismsFamily of B,A st
P is empty projection-morphisms by Th2;
hence thesis by Def10;
end;
theorem
for C being category, A being ObjectsFamily of I,C,
C1,C2 being object of C
st C1 is A-CatProduct-like & C2 is A-CatProduct-like
holds C1,C2 are_iso
proof
let C be category;
let A be ObjectsFamily of I,C;
let C1,C2 be object of C;
assume that
C1: C1 is A-CatProduct-like and
C2: C2 is A-CatProduct-like;
per cases;
suppose I is empty;
hence thesis by C1,C2,ALTCAT_3:28;
end;
suppose I is non empty;
then reconsider I as non empty set;
reconsider A as ObjectsFamily of I,C;
consider P1 being MorphismsFamily of C1,A such that
A1: P1 is feasible and
A2: P1 is projection-morphisms by C1,Def10;
consider P2 being MorphismsFamily of C2,A such that
A3: P2 is feasible and
A4: P2 is projection-morphisms by C2,Def10;
consider f1 being Morphism of C2,C1 such that
A5: f1 in <^C2,C1^> and
A6: for i being Element of I holds P2.i = P1.i * f1 and
for fa being Morphism of C2,C1 st
for i being Element of I holds P2.i = P1.i * fa
holds f1 = fa by A2,A3,Def8;
consider g1 being Morphism of C1,C1 such that
g1 in <^C1,C1^> and
for i being Element of I holds P1.i = P1.i * g1 and
A7: for fa being Morphism of C1,C1 st
for i being Element of I holds P1.i = P1.i * fa
holds g1 = fa by A1,A2,Def8;
consider f2 being Morphism of C1,C2 such that
A8: f2 in <^C1,C2^> and
A9: for i being Element of I holds P1.i = P2.i * f2 and
for fa being Morphism of C1,C2 st
for i being Element of I holds P1.i = P2.i * fa
holds f2 = fa by A1,A4,Def8;
consider g2 being Morphism of C2,C2 such that
g2 in <^C2,C2^> and
for i being Element of I holds P2.i = P2.i * g2 and
A10: for fa being Morphism of C2,C2 st
for i being Element of I holds P2.i = P2.i * fa
holds g2 = fa by A3,A4,Def8;
thus <^C1,C2^> <> {} & <^C2,C1^> <> {} by A5,A8;
take f2;
A11: f2 is retraction
proof
take f1;
now
let i be Element of I;
P2.i in <^C2,A.i^> by A3,Def6;
hence P2.i = P2.i * idm C2 by ALTCAT_1:def 17;
end;
then
A12: g2 = idm C2 by A10;
now
let i be Element of I;
P2.i in <^C2,A.i^> by A3,Def6;
hence P2.i * (f2 * f1) = P2.i * f2 * f1 by A5,A8,ALTCAT_1:21
.= P1.i * f1 by A9
.= P2.i by A6;
end;
hence f2 * f1 = idm C2 by A12,A10;
end;
f2 is coretraction
proof
take f1;
now
let i be Element of I;
P1.i in <^C1,A.i^> by A1,Def6;
hence P1.i = P1.i * idm C1 by ALTCAT_1:def 17;
end;
then
A13: g1 = idm C1 by A7;
now
let i be Element of I;
P1.i in <^C1,A.i^> by A1,Def6;
hence P1.i * (f1 * f2) = P1.i * f1 * f2 by A5,A8,ALTCAT_1:21
.= P2.i * f2 by A6
.= P1.i by A9;
end;
hence f1 * f2 = idm C1 by A13,A7;
end;
hence thesis by A5,A8,A11,ALTCAT_3:6;
end;
end;
reserve A for ObjectsFamily of I,EnsCat E;
definition
let I,E,A;
assume
A1: product A in E;
func EnsCatProductObj A -> object of EnsCat E equals :Def11:
product A;
coherence by A1,ALTCAT_1:def 14;
end;
definition
let I,E,A;
assume
A1: product A in E;
func EnsCatProduct A -> MorphismsFamily of EnsCatProductObj A,A
means :Def12:
for i being set st i in I holds it.i = proj(A,i);
existence
proof
deffunc F(set) = proj(A,$1);
consider P being ManySortedSet of I such that
A2: for i being set st i in I holds P.i = F(i) from PBOOLE:sch 4;
set B = EnsCatProductObj A;
A3: B = product A by A1,Def11;
P is MorphismsFamily of B,A
proof
let i be set such that
A4: i in I;
reconsider I as non empty set by A4;
reconsider i as Element of I by A4;
reconsider A as ObjectsFamily of I,EnsCat E;
take A.i;
A5: <^B,A.i^> = Funcs(B,A.i) by ALTCAT_1:def 14;
dom A = I by PARTFUN1:def 2;
then
A6: rng proj(A,i) c= A.i by YELLOW17:3;
dom proj(A,i) = B by A3,PARTFUN1:def 2;
then proj(A,i) in Funcs(B,A.i) by A6,FUNCT_2:def 2;
hence thesis by A2,A5;
end;
then reconsider P as MorphismsFamily of B,A;
take P;
thus thesis by A2;
end;
uniqueness
proof
let f,g be MorphismsFamily of EnsCatProductObj A,A such that
A7: for i being set st i in I holds f.i = proj(A,i) and
A8: for i being set st i in I holds g.i = proj(A,i);
now
let i be set;
assume
A9: i in I;
hence f.i = proj(A,i) by A7
.= g.i by A8,A9;
end;
hence thesis by PBOOLE:3;
end;
end;
theorem Th7:
product A in E & product A = {} implies EnsCatProduct A = I --> {}
proof
assume that
A1: product A in E and
A2: product A = {};
now
let i be set;
assume
A3: i in I;
hence (EnsCatProduct A).i = proj(A,i) by A1,Def12
.= {} by A2
.= (I --> {}).i by A3,FUNCOP_1:7;
end;
hence thesis by PBOOLE:3;
end;
theorem Ta1:
product A in E implies EnsCatProduct A is feasible projection-morphisms
proof
set B = EnsCatProductObj A;
set P = EnsCatProduct A;
assume
A1: product A in E; then
A2: B = product A by Def11;
per cases;
suppose
A3: product A <> {};
A4: dom A = I by PARTFUN1:def 2;
A5: now
let i be set;
assume i in I;
then A.i in rng A by A4,FUNCT_1:def 3;
hence A.i <> {} by A3,CARD_3:26;
end;
thus P is feasible
proof
let i be set;
assume
A6: i in I;
then reconsider I as non empty set;
reconsider i as Element of I by A6;
reconsider A as ObjectsFamily of I,EnsCat E;
reconsider P as MorphismsFamily of B,A;
take A.i;
A7: <^B,A.i^> = Funcs(B,A.i) by ALTCAT_1:def 14;
A.i <> {} by A5;
then Funcs(B,A.i) <> {};
then P.i in <^B,A.i^> by A7;
hence thesis;
end;
let X be object of EnsCat E, F be MorphismsFamily of X,A;
assume F is feasible;
A8: <^X,B^> = Funcs(X,B) by ALTCAT_1:def 14;
defpred P[set,set] means
ex M being ManySortedSet of I st
(for i being set st i in I holds M.i = F.i.$1) & $2 = M;
A9: for x being set st x in X ex u being set st P[x,u]
proof
let x be set;
assume x in X;
deffunc I(set) = F.$1.x;
consider f being ManySortedSet of I such that
A10: for i being set st i in I holds f.i = I(i) from PBOOLE:sch 4;
take f,f;
thus thesis by A10;
end;
consider ff being Function such that
A11: dom ff = X and
A12: for x being set st x in X holds P[x,ff.x] from CLASSES1:sch 1(A9);
A13: rng ff c= B
proof
let y be element;
assume y in rng ff;
then consider x being set such that
A14: x in dom ff and
A15: ff.x = y by FUNCT_1:def 3;
consider M being ManySortedSet of I such that
A16: for i being set st i in I holds M.i = F.i.x and
A17: ff.x = M by A11,A12,A14;
A18: dom M = I by PARTFUN1:def 2;
now
let i be set;
assume
A19: i in dom A;
then reconsider I as non empty set;
reconsider j = i as Element of I by A19;
reconsider A1 = A as ObjectsFamily of I,EnsCat E;
reconsider F1 = F as MorphismsFamily of X,A1;
A20: <^X,A1.j^> = Funcs(X,A1.j) by ALTCAT_1:def 14;
A1.j <> {} by A5;
then
A21: dom(F1.j) = X & rng(F1.j) c= A1.j by A20,FUNCT_2:92;
then
A22: F1.j.x in rng(F1.j) by A14,A11,FUNCT_1:def 3;
M.j = F.j.x by A16;
hence M.i in A.i by A22,A21;
end;
hence thesis by A2,A4,A15,A17,A18,CARD_3:9;
end;
then reconsider ff as Morphism of X,B by A8,A11,FUNCT_2:def 2;
take ff;
thus
A23: ff in <^X,B^> by A8,A13,A11,FUNCT_2:def 2;
thus for i being set st i in I
ex si being object of EnsCat E, Pi being Morphism of B,si st
si = A.i & Pi = P.i & F.i = Pi * ff
proof
let i be set;
assume
A24: i in I;
then reconsider I as non empty set;
reconsider j = i as Element of I by A24;
reconsider A1 = A as ObjectsFamily of I,EnsCat E;
reconsider P1 = P as MorphismsFamily of B,A1;
reconsider F1 = F as MorphismsFamily of X,A1;
take A1.j;
take P1.j;
thus A1.j = A.i & P1.j = P.i;
reconsider p = P1.j as Function;
A25: <^B,A1.j^> = Funcs(B,A1.j) by ALTCAT_1:def 14;
A26: A1.j <> {} by A5;
then <^X,A1.j^> <> {} by A25,A23,ALTCAT_1:def 2;
then
A27: P1.j * ff = p * ff by A23,A26,A25,ALTCAT_1:16;
A28: <^X,A1.j^> = Funcs(X,A1.j) by ALTCAT_1:def 14;
then
A29: dom(P1.j*ff) = X by A26,FUNCT_2:92;
A30: dom(F1.j) = X by A26,A28,FUNCT_2:92;
now
let x be set;
assume
A31: x in dom(F1.j);
then consider M being ManySortedSet of I such that
A32: for i being set st i in I holds M.i = F.i.x and
A33: ff.x = M by A12,A30;
A34: dom proj(A,j) = B by A2,CARD_3:def 16;
A35: ff.x in rng ff by A11,A30,A31,FUNCT_1:def 3;
thus (p*ff).x = p.(ff.x) by A11,A30,A31,FUNCT_1:13
.= proj(A,j).(ff.x) by A1,Def12
.= M.j by A33,A34,A35,A13,CARD_3:def 16
.= F1.j.x by A32;
end;
hence F.i = P1.j * ff by A27,A29,A26,A28,FUNCT_2:92,FUNCT_1:2;
end;
let f1 be Morphism of X,B such that
A36: for i being set st i in I
ex si being object of EnsCat E, Pi being Morphism of B,si st
si = A.i & Pi = P.i & F.i = Pi * f1;
A37: f1 is Function of X,B by A8,A23,FUNCT_2:66;
then
A38: dom f1 = X by A3,A2,FUNCT_2:def 1;
A39: rng f1 c= B by A37,RELAT_1:def 19;
now
let x be set;
assume
A40: x in dom ff;
then
A41: f1.x in rng f1 by A11,A38,FUNCT_1:def 3;
reconsider h = f1.x as Function by A2,A37;
consider M being ManySortedSet of I such that
A42: for i being set st i in I holds M.i = F.i.x and
A43: ff.x = M by A11,A12,A40;
A44: dom h = I by A2,A4,A41,A39,CARD_3:9;
now
let i be set;
assume
A45: i in dom M;
then consider si being object of EnsCat E, Pi being Morphism of B,si
such that
A46: si = A.i & Pi = P.i and
A47: F.i = Pi * f1 by A36;
A48: P.i = proj(A,i) by A1,A45,Def12;
A49: dom proj(A,i) = B by A2,CARD_3:def 16;
A50: <^B,si^> = Funcs(B,si) by ALTCAT_1:def 14;
A51: si <> {} by A5,A45,A46;
then
A52: <^X,si^> <> {} by A50,A23,ALTCAT_1:def 2;
thus M.i = (Pi*f1).x by A47,A42,A45
.= (Pi qua Function*f1).x by A50,A23,A51,A52,ALTCAT_1:16
.= Pi.h by A38,A11,A40,FUNCT_1:13
.= h.i by A39,A41,A46,A48,A49,CARD_3:def 16;
end;
hence ff.x = f1.x by A44,A43,FUNCT_1:2,PARTFUN1:def 2;
end;
hence thesis by A11,A38,FUNCT_1:2;
end;
suppose
A53: product A = {};
thus P is feasible
proof
let i be set such that
A54: i in I;
reconsider I as non empty set by A54;
reconsider i as Element of I by A54;
reconsider A as ObjectsFamily of I,EnsCat E;
take A.i;
A55: <^B,A.i^> = Funcs(B,A.i) by ALTCAT_1:def 14
.= {{}} by A2,A53,FUNCT_5:57;
P.i = (I-->{}).i by A1,A53,Th7
.= {} by FUNCOP_1:7;
hence thesis by A55,TARSKI:def 1;
end;
let X be object of EnsCat E, F be MorphismsFamily of X,A;
assume
A56: F is feasible;
A57: now
assume
A58: X <> {};
{} in rng A by A53,CARD_3:26;
then consider i being set such that
A59: i in dom A and
A60: A.i = {} by FUNCT_1:def 3;
reconsider I as non empty set by A59;
reconsider i as Element of I by A59;
reconsider A as ObjectsFamily of I,EnsCat E;
<^X,A.i^> = Funcs(X,A.i) by ALTCAT_1:def 14
.= {} by A58,A60;
hence contradiction by A56,Def6;
end;
A61: <^X,B^> = Funcs(X,B) by ALTCAT_1:def 14
.= {{}} by A57,FUNCT_5:57;
then reconsider f = {} as Morphism of X,B by TARSKI:def 1;
take f;
thus f in <^X,B^> by A61;
thus for i being set st i in I
ex si being object of EnsCat E, Pi being Morphism of B,si st
si = A.i & Pi = P.i & F.i = Pi * f
proof
let i be set such that
A62: i in I;
reconsider J = I as non empty set by A62;
reconsider j = i as Element of J by A62;
reconsider A1 = A as ObjectsFamily of J,EnsCat E;
reconsider P1 = P as MorphismsFamily of B,A1;
reconsider si = A1.j as object of EnsCat E;
reconsider Pi = P1.j as Morphism of B,si;
reconsider F1 = F as MorphismsFamily of X,A1;
reconsider F2 = F1.j as Morphism of X,si;
take si, Pi;
thus si = A.i & Pi = P.i;
A63: <^B,si^> = Funcs(B,si) by ALTCAT_1:def 14
.= {{}} by A2,A53,FUNCT_5:57;
then
A64: <^X,si^> <> {} by A61,ALTCAT_1:def 2;
A65: Funcs(X,si) = {{}} by A57,FUNCT_5:57;
A66: <^X,si^> = Funcs(X,si) by ALTCAT_1:def 14;
thus F.i = F2
.= {} by A65,A66,TARSKI:def 1
.= Pi qua Function * f
.= Pi * f by A63,A61,A64,ALTCAT_1:16;
end;
let f1 be Morphism of X,B;
thus thesis by A61,TARSKI:def 1;
end;
end;
theorem
product A in E implies EnsCatProductObj A is A-CatProduct-like
proof
assume
A1: product A in E;
take EnsCatProduct A;
thus thesis by A1,Ta1;
end;
theorem
(for I,A holds product A in E) implies EnsCat E is with_products
proof
assume
A0: for I,A holds product A in E;
let I,A;
take EnsCatProductObj A, EnsCatProduct A;
product A in E by A0;
hence thesis by Ta1;
end;