<Chapter Id="intro">
<TITLE>Introduction</TITLE>

<Para>
     This document is the user  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, 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>

<Sect1>
<Title> What is <ProductName>Postgres</ProductName>?</Title>

<Para>
     Traditional   relational  database  management  systems
     (DBMSs) 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 "Spartan simplicity".
     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 four additional
     basic concepts in such a way that  users  can  easily
     extend the system:

<SimpleList>
<Member>classes</Member>
<Member>inheritance</Member>
<Member>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>.

</Sect1>

&history;

&about;

&info;

&legal;

</Chapter>
