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<!--
$Header: /cvsroot/pgsql/doc/src/sgml/intro.sgml,v 1.14 2001/02/03 19:03:27 petere Exp $
-->
<preface id="preface">
<title>Preface</title>
<sect1 id="intro-whatis">
<title> What is <productname>PostgreSQL</productname>?</title>
<para>
<productname>PostgreSQL</productname> is an object-relational
database management system (<acronym>ORDBMS</acronym>) based on
<ulink url="http://s2k-ftp.CS.Berkeley.EDU:8000/postgres/postgres.html">
<productname>POSTGRES, Version 4.2</productname></ulink>,
developed at the University of California at Berkeley Computer
Science Department. The <productname>POSTGRES</productname>
project, led by Professor Michael Stonebraker, was 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>
<productname>PostgreSQL</productname> is an open-source descendant of
this original Berkeley code. It provides SQL92/SQL99 language support
and other modern features.
</para>
<para>
<productname>POSTGRES</productname> pioneered many of the
object-relational concepts now becoming available in some commercial
databases.
Traditional relational database management systems
(<acronym>RDBMS</acronym>) support a data model consisting of a collection
of named relations, containing attributes of a specific
type. In current commercial systems, possible types
include floating point numbers, integers, character
strings, money, and dates. It is commonly recognized
that this model is inadequate for future data
processing applications.
The relational model successfully replaced previous
models in part because of its <quote>Spartan simplicity</quote>.
However, as mentioned, this simplicity often makes the
implementation of certain applications very difficult.
<productname>Postgres</productname> offers substantial additional
power by incorporating the following additional
concepts in such a way that users can easily
extend the system:
<simplelist>
<member>inheritance</member>
<member>data types</member>
<member>functions</member>
</simplelist>
</para>
<para>
Other features provide additional power and flexibility:
<simplelist>
<member>constraints</member>
<member>triggers</member>
<member>rules</member>
<member>transaction integrity</member>
</simplelist>
</para>
<para>
These features put <productname>Postgres</productname> into the
category of databases referred to as
<firstterm>object-relational</firstterm>. Note that this is distinct
from those referred to as <firstterm>object-oriented</firstterm>,
which in general are not as well suited to supporting the
traditional relational database languages.
So, although <productname>Postgres</productname> has some
object-oriented features, it is firmly in the relational database
world. In fact, some commercial databases have recently
incorporated features pioneered by <productname>Postgres</productname>.
</para>
</sect1>
&history;
&info;
¬ation;
&problems;
&y2k;
</preface>
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