 <chapter id="intro-pg">
  <title>Introduction</title>

  <para>
   This document is the programmer's  manual  for  the  
   <ulink url="http://postgresql.org/"><productname>PostgreSQL</productname></ulink>
   database  management system, originally developed at the University
   of California at Berkeley.

   <productname>PostgreSQL</productname>  is  based  on
   <ulink url="http://s2k-ftp.CS.Berkeley.EDU:8000/postgres/postgres.html">
    <productname>Postgres release 4.2</productname></ulink>. 
   The <productname>Postgres</productname> project, 
   led by Professor Michael Stonebraker, has been sponsored  by  the
   Defense  Advanced Research Projects Agency (<acronym>DARPA</acronym>), the
   Army Research Office (<acronym>ARO</acronym>), the National Science  
   Foundation (<acronym>NSF</acronym>), and ESL, Inc.
  </para>

  <para>
   The first part of this manual 
   explains  the <productname>Postgres</productname>  
   approach  to  extensibility  and describe how
   users can extend <productname>Postgres</productname> 
   by adding user-defined types,
   operators, aggregates, and both query language and programming 
   language functions.
   After a discussion  of  the <productname>Postgres</productname> 
   rule system, we discuss
   the trigger and SPI interfaces.
   The manual concludes with a detailed description of 
   the programming interfaces and
   support libraries for various languages.
  </para>

  <para>
   We assume proficiency with Unix and C programming.
  </para>

   &info;
   &notation;
   &y2k;
   &legal;

 </chapter>

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