@techreport{TR-DCC-93-27,
  number = {DCC-93-27},
  author = {Meidanis, João},
  title = {A Unified Characterization of Chordal, Interval, Indifference, and Other Classes of Graphs},
  month = {September},
  year = {1993}, 
  institution = {Department of Computer Science, University of Campinas},
  note = {In English, 17 pages.
    \par\selectlanguage{english}\textbf{Abstract}
      Motivated by very similar characterizations given in the
      literature for chordal, interval, and indifference graphs we
      introduce a way of defining classes of graphs in terms of boolean
      functions of two variables.  Each such function originates a class
      of graphs.  Denoting the variables by ${\bf 1}$ and ${\bf 2}$, the
      functions ${\bf 1}\Rightarrow{\bf 2}$, ${\bf 1}$, and ${\bf
      1}\wedge{\bf 2}$ originate the classes of chordal, interval, and
      indifference graphs, respectively.  In this paper we study the
      classes corresponding to all other boolean functions, as well as
      general properties of these classes.  A satisfactory
      identification of the class corresponding to function ${\bf
      1}\oplus{\bf 2}$ (exclusive or) is still open.
  }
}