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      look at <command>rclzip</command> which uses Zip file paths as

      internal identifiers (<literal>ipath</literal>), and

      <command>rclinfo</command>, which uses an integer index.</para> 

      <sect2 id="rcl.program.filters.simple">

        <title>Simple filters</title>

        no way necessary. Extracting the text from the native format is the

        difficult part. Outputting the format expected by &RCL; is

        text extractors which can be called from the filter. In some cases

        the output of the translating program is completely appropriate,

        and no intermediate shell-script is needed.</para>

      <para>When writing a filter, you should decide if it will output

      plain text or html. Plain text is simpler, but you will not be able

      to add metadata or vary the output character encoding (this will be

      defined in a configuration file). Additionally, some formatting may

      easier to preserve when previewing html. Actually the deciding factor

      is metadata: &RCL; has a way to <link linkend="rcl.program.filters.html">

      extract metadata from the html header and use it for field 

      searches.</link>.</para>

        variable (values <literal>yes</literal>, <literal>no</literal>)

        tells the filter if the operation is for indexing or

        format, for example stripping uninteresting repeated keywords (ie:

        <literal>Subject:</literal> for email) when indexing. This is not

        essential.</para>

      <para>You should look to one of the simple filters, for exemple

        <literal>rclps</literal> for a starting point.</para>

        <para>Don't forget to make your filter executable before 

         testing !</para>

      </sect2>

      <sect2 id="rcl.program.filters.association">

        <title>Telling &RCL; about the filter</title>

      <para>There are two elements that link a file to the filter which

      should process it: the association of file to mime type and the

      association of a mime type with a filter.</para>

      <para>The association of files to mime types is mostly based on

        name suffixes. The types are defined inside the

        <link linkend="rcl.install.config.mimeconf">

        <filename>mimemap</filename> file</link>. Example:

<programlisting>

.doc = application/msword

</programlisting>

       If no suffix association is found for the file name, &RCL; will try

       to execute the <command>file -i</command> command to determine a

       mime type.</para>

      the <link linkend="rcl.install.config.mimemap">

      of better help than a long explanation:</para>

       </para> 

      </sect2>