@techreport{TR-DCC-93-15,
  number = {DCC-93-15},
  author = {Mendonça, Nabor C. and Anido, Ricardo O.},
  title = {Using Extended Hierarchical Quorum Consensus to Control Replicated Data: {From} Traditional Voting to Logical Structures},
  month = {June},
  year = {1993}, 
  institution = {Department of Computer Science, University of Campinas},
  note = {In English, 24 pages.
    \par\selectlanguage{english}\textbf{Abstract}
      In large distributed computing systems, where copies of the same
      logical data are stored at many different sites, the replica
      control protocol must reduce communication costs when forming the
      quorums required at each access to the replicated data, in order
      to improve the system response time.  An interesting way to
      achieve this reduction is to organize the copies into some logical
      structure, like a grid or a tree, and then to use this structure
      to form smaller quorums.  Another example of a structure used to
      form smaller quorums is a generic tree in which only the leaves
      correspond to copies of the replicated data.
    \par
      This paper presents a new replica control protocol that logically
      organizes the copies as leaves of a generic tree, but introduces
      the {\em blind-write} as another operation (besides the
      traditional read and write) defined over the replicated data.
      With this third operation, the proposed protocol turns out to be a
      generalization of the traditional voting scheme and others
      existing protocols that use a symmetrical logical structure (i.e.,
      a structure in which the responsibility for controlling the
      replicated data is equally shared by all copies) to form the
      access quorums.  The proposed protocol also makes possible to
      achieve better relations between quorums size and the total number
      of copies, even under high availability requirements.
  }
}