MODELS OF MULTIUSER WRITE-EFFICIENT MEMORIES AND GENERAL DIAMETRIC THEOREMS

Write-efficient memories (WEM) were introduced by Ahlswede/Zhang as a model for storing and updating information an a rewritable medium. We strengthen the capacity theorem by providing a full control of the rat es of the spreads, Next we address and settle the storage capacity reg ion problem under the average costs constraint for the case of many us ers who write on the memory in an arbitrary order, where neither the e ncoder nor the decoder knows the previous content of the memory, The c ombinatorial essence is a diametric theorem for several families. Fina lly we present a storage capacity theorem for several persons using th e memory in cyclic order. (C) 1997 Academic Press.