:: deftheorem Def15 defines @ OSAFREE:def 15 :
for S being locally_directed OrderSortedSign
for X being non-empty ManySortedSet of S
for t being Symbol of (DTConOSA X) st ex p being FinSequence st t ==> p holds
for b₄ being OperSymbol of S holds
( b₄ = @ (X,t) iff [b₄, the carrier of S] = t );