Multitape AFA

Abstract
Device representations, via multitape AFA (abstract families of acceptors), are given for the families of languages which result from applying the wedge (A) m)d the substitu- tion operations to AFL (abstract families of languages). In particular, if ~ and ~2 are multi- tape AFA (i.e. certain families of multistorage tape acceptors), then 5)~ A ~2 is defined as the family of multitape acceptors which results when the tapes of ~ and ~2 are coalesced, with the ~-tapes preceding those in ~2 . It is shown that the smallest full AFL containing 2(~) A 2 (~D2) = {L~ N L2 ILi in2 (~Di) } is ,12 (~ h~:). For each multitape AFAr, aset ~.v of "nested" multitape acceptors is defined. It is shown that if ~ and ~2 are single-tape AFA, then the family of languages obtained from (~ A ~2) N is the family of langnages obtained by substitut- ing the AFL defined by ~2 into the AFL defined by ~D~ .

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