m class="acronym">ARO</acronym>), the National Science Foundation
   (<acronym class="acronym">NSF</acronym>), and ESL, Inc.  The implementation of
   <span class="productname">POSTGRES</span> began in 1986.  The initial
   concepts for the system were presented in <a class="xref" href="biblio.html#STON86">[ston86]</a>,
   and the definition of the initial data model appeared in <a class="xref" href="biblio.html#ROWE87">[rowe87]</a>.  The design of the rule system at that time was
   described in <a class="