let C be category; :: thesis: ( ( for o1, o2 being Object of C
for m being Morphism of o1,o2 holds m is epi ) implies AltCatStr(# the carrier of C, the Arrows of C, the Comp of C #) = AllEpi C )
assume A1: for o1, o2 being Object of C
for m being Morphism of o1,o2 holds m is epi ; :: thesis: AltCatStr(# the carrier of C, the Arrows of C, the Comp of C #) = AllEpi C
A2: the carrier of (AllEpi C) = the carrier of AltCatStr(# the carrier of C, the Arrows of C, the Comp of C #) by Def2;
A3: the Arrows of (AllEpi C) cc= the Arrows of C by Def2;

now :: thesis: for i being object st i in [: the carrier of C, the carrier of C:] holds
the Arrows of (AllEpi C) . i = the Arrows of C . i

let i be object ; :: thesis: ( i in [: the carrier of C, the carrier of C:] implies the Arrows of (AllEpi C) . i = the Arrows of C . i )
assume A4: i in [: the carrier of C, the carrier of C:] ; :: thesis: the Arrows of (AllEpi C) . i = the Arrows of C . i
then consider o1, o2 being object such that
A5: ( o1 in the carrier of C & o2 in the carrier of C ) and
A6: i = [o1,o2] by ZFMISC_1:84;
reconsider o1 = o1, o2 = o2 as Object of C by A5;
thus the Arrows of (AllEpi C) . i = the Arrows of C . i :: thesis: verum

proof

thus the Arrows of (AllEpi C) . i c= the Arrows of C . i by A2, A3, A4; :: according to XBOOLE_0:def 10 :: thesis: the Arrows of C . i c= the Arrows of (AllEpi C) . i
let n be object ; :: according to TARSKI:def 3 :: thesis: ( not n in the Arrows of C . i or n in the Arrows of (AllEpi C) . i )
assume A7: n in the Arrows of C . i ; :: thesis: n in the Arrows of (AllEpi C) . i
then reconsider n1 = n as Morphism of o1,o2 by A6;
n1 is epi by A1;
then n in the Arrows of (AllEpi C) . (o1,o2) by A6, A7, Def2;
hence n in the Arrows of (AllEpi C) . i by A6; :: thesis: verum

end;

end;

hence AltCatStr(# the carrier of C, the Arrows of C, the Comp of C #) = AllEpi C by A2, ALTCAT_2:25, PBOOLE:3; :: thesis: verum