:: deftheorem Def1 defines support GROUP_19:def 1 :
for I being set
for F being Group-Family of I
for a being Function
for b₄ being Subset of I holds
( b₄ = support (a,F) iff for i being object holds
( i in b₄ iff ( a . i <> 1_ (F . i) & i in I ) ) );