let PTN be PT_net_Str ; :: thesis: for M0 being Boolean_marking of PTN
for t being transition of PTN holds
( t is_firable_on M0 iff <*t*> is_firable_on M0 )

let M0 be Boolean_marking of PTN; :: thesis: for t being transition of PTN holds
( t is_firable_on M0 iff <*t*> is_firable_on M0 )

let t be transition of PTN; :: thesis: ( t is_firable_on M0 iff <*t*> is_firable_on M0 )
hereby :: thesis: ( <*t*> is_firable_on M0 implies t is_firable_on M0 )
assume A1: t is_firable_on M0 ; :: thesis: <*t*> is_firable_on M0
set M = <*(Firing (<*t*> /. 1),M0)*>;
A2: len <*t*> = 1 by FINSEQ_1:56
.= len <*(Firing (<*t*> /. 1),M0)*> by FINSEQ_1:56 ;
A3: <*t*> /. 1 is_firable_on M0 by A1, FINSEQ_4:25;
A4: <*(Firing (<*t*> /. 1),M0)*> /. 1 = Firing (<*t*> /. 1),M0 by FINSEQ_4:25;
now
let i be Element of NAT ; :: thesis: ( i < len <*t*> & i > 0 implies ( <*t*> /. (i + 1) is_firable_on <*(Firing (<*t*> /. 1),M0)*> /. i & <*(Firing (<*t*> /. 1),M0)*> /. (i + 1) = Firing (<*t*> /. (i + 1)),(<*(Firing (<*t*> /. 1),M0)*> /. i) ) )
assume A5: ( i < len <*t*> & i > 0 ) ; :: thesis: ( <*t*> /. (i + 1) is_firable_on <*(Firing (<*t*> /. 1),M0)*> /. i & <*(Firing (<*t*> /. 1),M0)*> /. (i + 1) = Firing (<*t*> /. (i + 1)),(<*(Firing (<*t*> /. 1),M0)*> /. i) )
len <*t*> = 0 + 1 by FINSEQ_1:56;
hence ( <*t*> /. (i + 1) is_firable_on <*(Firing (<*t*> /. 1),M0)*> /. i & <*(Firing (<*t*> /. 1),M0)*> /. (i + 1) = Firing (<*t*> /. (i + 1)),(<*(Firing (<*t*> /. 1),M0)*> /. i) ) by A5, NAT_1:13; :: thesis: verum
end;
hence <*t*> is_firable_on M0 by A2, A3, A4, Def4; :: thesis: verum
end;
assume <*t*> is_firable_on M0 ; :: thesis: t is_firable_on M0
then consider M being FinSequence of Bool_marks_of PTN such that
len <*t*> = len M and
A6: <*t*> /. 1 is_firable_on M0 and
( M /. 1 = Firing (<*t*> /. 1),M0 & ( for i being Element of NAT st i < len <*t*> & i > 0 holds
( <*t*> /. (i + 1) is_firable_on M /. i & M /. (i + 1) = Firing (<*t*> /. (i + 1)),(M /. i) ) ) ) by Def4;
thus t is_firable_on M0 by A6, FINSEQ_4:25; :: thesis: verum