:: deftheorem defines ==>* REWRITE3:def 6 :
for E being non empty set
for F being Subset of (E ^omega)
for TS being non empty transition-system over F
for x1, x2, y1, y2 being object holds
( x1,x2 ==>* y1,y2,TS iff ==>.-relation TS reduces [x1,x2],[y1,y2] );