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 <appendix id="external-projects">
  <title>External Projects</title>

  <para>
   <productname>PostgreSQL</productname> is a complex software project,
   and managing the project is difficult. We have found that many
   enhancements to <productname>PostgreSQL</productname> can be more
   efficiently developed separately from the core project.
  </para>

  <para>
   To help our community with the development of their external projects, we
   have created <ulink url="http://www.pgfoundry.org/">PgFoundry</ulink>, a
   website that provides hosting for <productname>PostgreSQL</>-related
   projects that are maintained outside the core <productname>PostgreSQL</>
   distribution. PgFoundry is built using the GForge software project and is
   similar to <ulink url="http://sourceforge.net">SourceForge.net</> in its
   feature set, providing mailing lists, forums, bug tracking, SCM, and web
   hosting. If you have a <productname>PostgreSQL</>-related open source
   project that you would like to have hosted at PgFoundy, please feel free
   to create a new project.
  </para>

 <sect1 id="external-interfaces">
  <title>Client Interfaces</title>

  <indexterm>
   <primary>interfaces</primary>
   <secondary>externally maintained</secondary>
  </indexterm>

  <para>
   There are only two client interfaces included in the base
   <productname>PostgreSQL</productname> distribution:
   <itemizedlist>
    <listitem>
     <para>
      <link linkend="libpq">libpq</link> is included because it is the
      primary C language interface, and because many other client interfaces
      are built on top of it.
     </para>
    </listitem>

    <listitem>
     <para>
      <link linkend="ecpg">ECPG</link> is included because it depends on the
      server-side SQL grammar, and is therefore sensitive to changes in
      <productname>PostgreSQL</productname> itself.
     </para>
    </listitem>
   </itemizedlist>

   All other language interfaces are external projects and are distributed
   separately. <xref linkend="language-interface-table"> includes a list of
   some of these projects. Note that some of these packages might not be
   released under the same license as <productname>PostgreSQL</>. For more
   information on each language interface, including licensing terms, refer to
   its website and documentation.
  </para>

  <table id="language-interface-table">
   <title>Externally Maintained Client Interfaces</>

   <tgroup cols="4">
    <thead>
     <row>
      <entry>Name</entry>
      <entry>Language</entry>
      <entry>Comments</entry>
      <entry>Website</entry>
     </row>
    </thead>

    <tbody>
     <row>
      <entry>DBD::Pg</entry>
      <entry>Perl</entry>
      <entry>Perl DBI driver</entry>
      <entry><ulink url="http://search.cpan.org/dist/DBD-Pg/">http://search.cpan.org/dist/DBD-Pg/</ulink></entry>
     </row>

     <row>
      <entry>JDBC</entry>
      <entry>JDBC</entry>
      <entry>Type 4 JDBC driver</entry>
      <entry><ulink url="http://jdbc.postgresql.org/">http://jdbc.postgresql.org/</ulink></entry>
     </row>

     <row>
      <entry>libpqxx</entry>
      <entry>C++</entry>
      <entry>New-style C++ interface</entry>
      <entry><ulink url="http://pqxx.org/">http://pqxx.org/</ulink></entry>
     </row>

     <row>
      <entry>Npgsql</entry>
      <entry>.NET</entry>
      <entry>.NET data provider</entry>
      <entry><ulink url="http://npgsql.projects.postgresql.org/">http://npgsql.projects.postgresql.org/</ulink></entry>
     </row>

     <row>
      <entry>ODBCng</entry>
      <entry>ODBC</entry>
      <entry>An alternative ODBC driver</entry>
      <entry><ulink url="http://projects.commandprompt.com/public/odbcng/">http://projects.commandprompt.com/public/odbcng/</ulink></entry>
     </row>

     <row>
      <entry>pgtclng</entry>
      <entry>Tcl</entry>
      <entry></entry>
      <entry><ulink url="http://pgfoundry.org/projects/pgtclng/">http://pgfoundry.org/projects/pgtclng/</ulink></entry>
     </row>

     <row>
      <entry>psqlODBC</entry>
      <entry>ODBC</entry>
      <entry>The most commonly-used ODBC driver</entry>
      <entry><ulink url="http://psqlodbc.projects.postgresql.org/">http://psqlodbc.projects.postgresql.org/</ulink></entry>
     </row>

     <row>
      <entry>psycopg</entry>
      <entry>Python</entry>
      <entry>DB API 2.0-compliant</entry>
      <entry><ulink url="http://www.initd.org/">http://www.initd.org/</ulink></entry>
     </row>
    </tbody>
   </tgroup>
  </table>
 </sect1>

 <sect1 id="external-pl">
  <title>Procedural Languages</title>

  <indexterm>
   <primary>procedural language</primary>
   <secondary>externally maintained</secondary>
  </indexterm>

  <para>
   <productname>PostgreSQL</productname> includes several procedural
   languages with the base distribution: <link
   linkend="plpgsql">PL/PgSQL</link>, <link linkend="pltcl">PL/Tcl</link>,
   <link linkend="plperl">PL/Perl</link>, and <link
   linkend="plpython">PL/Python</link>.
  </para>

  <para>
   In addition, there are a number of procedural languages that are developed
   and maintained outside the core <productname>PostgreSQL</productname>
   distribution. <xref linkend="pl-language-table"> lists some of these
   packages. Note that some of these projects might not be released under the same
   license as <productname>PostgreSQL</>. For more information on each
   procedural language, including licensing information, refer to its website
   and documentation.
  </para>

  <table id="pl-language-table">
   <title>Externally Maintained Procedural Languages</title>

   <tgroup cols="3">
    <thead>
     <row>
      <entry>Name</entry>
      <entry>Language</entry>
      <entry>Website</entry>
     </row>
    </thead>

    <tbody>
     <row>
      <entry>PL/Java</entry>
      <entry>Java</entry>
      <entry><ulink url="http://pljava.projects.postgresql.org/">http://pljava.projects.postgresql.org/</ulink></entry>
     </row>

     <row>
      <entry>PL/PHP</entry>
      <entry>PHP</entry>
      <entry><ulink url="http://www.commandprompt.com/community/plphp/">http://www.commandprompt.com/community/plphp/</ulink></entry>
     </row>

     <row>
      <entry>PL/Py</entry>
      <entry>Python</entry>
      <entry><ulink url="http://python.projects.postgresql.org/">http://python.projects.postgresql.org/</ulink></entry>
     </row>

     <row>
      <entry>PL/R</entry>
      <entry>R</entry>
      <entry><ulink url="http://www.joeconway.com/plr/">http://www.joeconway.com/plr/</ulink></entry>
     </row>

     <row>
      <entry>PL/Ruby</entry>
      <entry>Ruby</entry>
      <entry><ulink url="http://raa.ruby-lang.org/project/pl-ruby/">http://raa.ruby-lang.org/project/pl-ruby/</ulink></entry>
     </row>

     <row>
      <entry>PL/Scheme</entry>
      <entry>Scheme</entry>
      <entry><ulink url="http://plscheme.projects.postgresql.org/">http://plscheme.projects.postgresql.org/</ulink></entry>
     </row>

     <row>
      <entry>PL/sh</entry>
      <entry>Unix shell</entry>
      <entry><ulink url="http://plsh.projects.postgresql.org/">http://plsh.projects.postgresql.org/</ulink></entry>
     </row>
    </tbody>
   </tgroup>
  </table>
 </sect1>
 
 <sect1 id="external-extensions">
 <title>Extensions</title>

  <indexterm>
   <primary>extensions</primary>
  </indexterm>

  <para>
   <productname>PostgreSQL</> is designed to be easily extensible. For
   this reason, extensions loaded into the database can function just
   like features that are packaged with the database. The
   <filename>contrib/</> directory shipped with the source code
   contains a large number of extensions. The <filename>README</> file
   in that directory contains a summary. They include conversion
   tools, full-text indexing, <acronym>XML</> tools, and additional
   data types and indexing methods. Other extensions are developed
   independently, like <application><ulink
   url="http://www.postgis.org/">PostGIS</ulink></>.  Even
   <productname>PostgreSQL</> replication solutions are developed
   externally. For example, <application> <ulink
   url="http://www.slony.info">Slony-I</ulink></> is a popular
   master/standby replication solution that is developed independently
   from the core project.
  </para>

  <para>
   There are several administration tools available for
   <productname>PostgreSQL</>. The most popular is
   <application><ulink url="http://www.pgadmin.org/">pgAdmin III</ulink></>, 
   and there are several commercially available ones as well.
  </para>
 </sect1>
</appendix>
