<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 an extremely  brief
     overview  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>

&notation;

&legal;

</Chapter>
