<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><!-- Keep this comment at the end of the fileLocal variables:mode: sgmlsgml-omittag:nilsgml-shorttag:tsgml-minimize-attributes:nilsgml-always-quote-attributes:tsgml-indent-step:1sgml-indent-data:tsgml-parent-document:nilsgml-default-dtd-file:"./reference.ced"sgml-exposed-tags:nilsgml-local-catalogs:"/usr/lib/sgml/CATALOG"sgml-local-ecat-files:nilEnd:-->