Thm* E:TaggedEventStruct, P,I,J,K:TraceProperty(E)
, R:(Trace(E) Trace(E) Prop).
tag_splitable(E;R) 
( tr_1,tr_2:Trace(E). (tr_1 R tr_2)  (tr_2 R tr_1)) 
R preserves P 
R preserves K 
( tr:Trace(E). (I K)(tr)  ( tr':Trace(E). I(tr') & J(tr') & (tr R tr'))) 
(((I J) K) fuses P)  ((I K) fuses P) | [normal_form_fusion] |