usermanual.sgml
2257 lines (1880 with data), 98.6 kB
<!DOCTYPE BOOK PUBLIC "-//FreeBSD//DTD DocBook V4.1-Based Extension//EN" [
<!ENTITY RCL "<application>Recoll</application>">
<!ENTITY XAP "<application>Xapian</application>">
]>
<book lang="en">
<bookinfo>
<title>Recoll user manual</title>
<author>
<firstname>Jean-Francois</firstname>
<surname>Dockes</surname>
<affiliation>
<address><email>jean-francois.dockes@wanadoo.fr</email></address>
</affiliation>
</author>
<copyright>
<year>2005</year>
<holder role="mailto:jean-francois.dockes@wanadoo.fr">Jean-Francois
Dockes</holder>
</copyright>
<releaseinfo>$Id: usermanual.sgml,v 1.50 2007-08-30 09:00:22 dockes Exp $</releaseinfo>
<abstract>
<para>This document introduces full text search notions
and describes the installation and use of the &RCL;
application. It currently describes &RCL; 1.9.</para>
</abstract>
</bookinfo>
<chapter id="rcl.introduction">
<title>Introduction</title>
<sect1 id="rcl.introduction.tryit">
<title>Giving it a try</title>
<para>If you do not like reading manuals (who does?) and would
like to give &RCL; a try, just perform <link
linkend="rcl.install.binary">installation</link> and start the
<command>recoll</command> user interface, which will index your
home directory by default, allowing you to search immediately after
indexing completes.</para>
<para>Do not do this if your home directory contains a huge
number of documents and you do not want to wait or are very
short on disk space. In this case, you may want to edit the <link
linkend="rcl.indexing.config">configuration file</link> first to
restrict the indexed area.</para>
<para>Also be aware that you may need to install the
appropriate <link linkend="rcl.install.external">
supporting applications</link> for document types that need
them (for example <application>antiword</application> for
ms-word files).</para>
<sect1 id="rcl.introduction.search">
<title>Full text search</title>
<para>&RCL; is a full text search application. Full text search
applications let you find your data by content rather
than by external attributes (like a file name). More
specifically, they will let you specify words (terms) that
should or should not appear in the text you are looking for,
and return a list of matching documents, ordered so that the
most <emphasis>relevant</emphasis> documents will appear
first.</para>
<para>You do not need to remember in what file or email message you
stored a given piece of information. You just ask for related
terms, and the tool will return a list of documents where
those terms are prominent, in a similar way to Internet search
engines.</para>
<para>&RCL; tries to determine which documents are most relevant to
the search terms you provide. Computer algorithms for determining
relevance can be very complex, and in general are inferior to the
power of the human mind to rapidly determine relevance. The quality
of relevance guessing by the search tool is probably the most
important element for a search application.</para>
<para>In many cases, you are looking for all the forms of a
word, not for a specific form or spelling. These different
forms may include plurals, different tenses for a verb, or
terms derived from the same root or <emphasis>stem</emphasis>
(example: floor, floors, floored, flooring...). &RCL; will by
default expand queries to all such related terms (words that
reduce to the same stem). This expansion can be disabled at
search time.</para>
<para>Stemming, by itself, does not accommodate for misspellings or
phonetic searches. &RCL; supports these features through a specific
tool (the <literal>term explorer</literal>) which will let you
explore the set of index terms along different modes.</para>
</sect1>
<sect1 id="rcl.introduction.recoll">
<title>Recoll overview</title>
<para>&RCL; uses the
<ulink url="http://www.xapian.org">&XAP;</ulink> information retrieval
library as its storage and retrieval engine. &XAP; is a very
mature package using <ulink
url="http://www.xapian.org/docs/intro_ir.html">a sophisticated
probabilistic ranking model</ulink>. &RCL; provides the interface
to get data into (indexing) and out (searching) of the system.</para>
<para>In practice, &XAP; works by remembering where terms appear
in your document files. The acquisition process is called
indexing. </para>
<para>The resulting index can be big (roughly the size of the
original document set), but it is not a document
archive. &RCL; can only display documents that still exist at
the place from which they were indexed. (Actually, there is a
way to reconstruct a document from the information in the
index, but the result is not nice, as all formatting,
punctuation and capitalization are lost).</para>
<para>&RCL; stores all internal data in <application>Unicode
UTF-8</application> format, and it can index files with
different character sets, encodings, and languages into the same
index. It has input filters for many document types.</para>
<para>Stemming depends on the document language. &RCL; stores
the unstemmed versions of terms and uses auxiliary databases for
term expansion. It can switch stemming languages, or add a
language, without re-indexing. Storing documents in different
languages in the same index is possible, and useful in
practice, but does introduce possibilities of confusion. &RCL;
currently makes no attempt at automatic language recognition.</para>
<para>&RCL; has many parameters which define exactly what to
index, and how to classify and decode the source
documents. These are kept in a <link
linkend="rcl.indexing.config">configuration file</link>. A
default configuration is copied into a standard location
(usually something like
<filename>/usr/[local/]share/recoll/examples</filename>)
during installation. The default parameters from this file may
be overridden by values that you set inside your personal
configuration, found by default in the
<filename>.recoll</filename> sub-directory of your home
directory. The default configuration will index your home
directory with default parameters and should be sufficient for
giving &RCL; a try, but you may want to adjust it
later.</para>
<para><link linkend="rcl.indexing.periodic.exec">Indexing</link>
is started automatically the first time you execute the
<command>recoll</command> search graphical user interface, or by
executing the <command>recollindex</command> command.</para>
<para><link linkend="rcl.search">Searches</link> are
performed inside the <command>recoll</command>
program, which has many options to help you find what you are
looking for.</para>
</sect1>
</chapter>
<chapter id="rcl.indexing">
<title>Indexing</title>
<sect1 id="rcl.indexing.introduction">
<title>Introduction</title>
<para>Indexing is the process by which the set of documents is
analyzed and the data entered into the database. &RCL; indexing
is normally incremental: documents will only be processed if
they have been modified. On the first execution, of course, all
documents will need processing. A full index build can be forced
later by specifying an option to the indexing command
(<command>recollindex -z</command>).</para>
<para>&RCL; indexing can be performed with two different
methods:</para>
<itemizedlist>
<listitem>
<formalpara><title>Periodic indexing:</title>
<para>indexing takes place at discrete
times, by executing the <command>recollindex</command>
command. The typical usage is to have a nightly indexing run
<link linkend="rcl.indexing.periodic.automat">programmed</link> into your
<command>cron</command> file.</para>
</formalpara>
</listitem>
<listitem>
<formalpara><title>Real time indexing:</title>
<para>indexing takes place as soon as a file is created or
changed. <command>recollindex</command> runs as a daemon
and uses a file system alteration monitor such as
<application>Fam</application>,
<application>Gamin</application> or
<application>inotify</application> do detect file changes.
Monitoring a big directory tree can consume significant
system resources.</para>
</formalpara>
</listitem>
</itemizedlist>
<para>The choice between the two methods is mostly a matter of
preference, and they can be combined by setting up multiple
indexes (ie: use periodic indexing on a big documentation
directory, and real time indexing on a small home
directory). Monitoring a big file system tree can consume
significant system resources, for dubious gains. <para>
<para>&RCL; knows about quite a few different document
types. The parameters for document types recognition and
processing are set in
<link linkend="rcl.indexing.config">configuration files</link>
Most file types, like HTML or word processing files, only hold
one document. Some file types, like mail folder files can hold
many individually indexed documents.
</para>
<para>&RCL; indexing processes plain text, HTML, openoffice
and e-mail files internally. Other types (ie: postscript, pdf,
ms-word, rtf) need external applications for preprocessing. The
list is in the <link linkend="rcl.install.external">
installation</link> section.</para>
<para>Without further configuration, &RCL; will index all
appropriate files from your home directory, with a reasonable
set of defaults.</para>
<para>In some cases, it may be interesting to index different
areas of the file system to separate databases. You can do this
by using multiple configuration directories, each indexing a
file system area to a specific database. See the <link
linkend="rcl.search.multidb">section about using multiple
databases</link> for more information on multiple configurations
and indexes. </para>
</sect1>
<sect1 id="rcl.indexing.storage">
<title>Index storage</title>
<para>The default location for the index data is the
<filename>xapiandb</filename> subdirectory of the &RCL;
configuration directory, typically
<filename>$HOME/.recoll/xapiandb/</filename>. This can be
changed via two different methods (with different purposes):</para>
<itemizedlist>
<listitem><para>You can specify a different configuration
directory by setting the <literal>RECOLL_CONFDIR</literal>
environment variable, or using the <literal>-c</literal>
option to the &RCL; commands. This method would typically be
used to index different areas of the file system to
different indexes. For example, if you were to issue the
following commands:
<programlisting>
export RECOLL_CONFDIR=~/.indexes-email
recoll
</programlisting> Then &RCL; would use configuration files
stored in <filename>~/.indexes-email/</filename> and,
(unless specified otherwise in
<filename>recoll.conf</filename>) would look for
the index in <filename>~/.indexes-email/xapiandb/</filename>.
<para>Using multiple configuration directories and
<link linkend="rcl.install.config.recollconf">configuration
options</link> allows you to tailor multiple configurations
and indexes to handle whatever subset of the available data
that you wish to make searchable.</para>
</listitem>
<listitem><para>You can also specify a different storage
location for the index by setting the <literal>dbdir</literal>
parameter in the configuration file
(see the <link linkend="rcl.install.config.recollconf">configuration
section</link>). This method would mainly be of use if you
wanted to keep the configuration directory in its default location,
but desired another location for the index, typically out of
disk occupation concerns.</para>
</listitem>
</itemizedlist>
<para>The size of the index is determined by the size of the set
of documents, but the ratio can vary a lot. For a typical mixed
set of documents, the index size will often be close to
the data set size. In specific cases (a set of compressed
mbox files for example), the index can become much bigger than
the documents. It may also be much smaller if the documents
contain a lot of images or other non-indexed data (an extreme
example being a set of mp3 files where only the tags would be
indexed).</para>
<para>Of course, images, sound and video do not increase the
index size, which means that it will be quite typical nowadays
(2006), that even a big index will be negligible against the
total amount of data on the computer.</para>
<para>The index data directory (<filename>xapiandb</filename>)
only contains data that can be completely rebuilt by an index
run, and it can always be destroyed safely.</para>
<sect2 id="rcl.indexing.storage.format">
<title>Index formats</title>
<para>&XAP; has had two possible index formats for quite some
time. The "old" one named <literal>Quartz</literal>, and the
new one named <literal>Flint</literal>. &XAP; 0.9 used
<literal>Quartz</literal> by default, but could use
<literal>Flint</literal> if a specific environment variable
(<literal>XAPIAN_PREFER_FLINT</literal>) was set. &XAP; 1.0
still supports <literal>Quartz</literal> but will use
<literal>Flint</literal> by default for new index
creations.</para>
<para>The number of disk accesses performed during indexing
has been much optimized in the new <literal>Flint</literal>
engine and you may see indexing times improved by 50% in some
cases (compared to <literal>Quartz</literal>), typically for
big indexes where disk accesses dominate the indexing
time. There is also a more modest improvement of index
size.</para>
<para>&XAP; will not convert automatically an existing index
from the <literal>Quartz</literal> to the
<literal>Flint</literal> format. If you have an older index
and want to take advantage of the new format (which can be
done without setting the environment variable as of &RCL;
1.8.2 and &XAP; 1.0.0), you will have to explicitely delete
the old index, then run a normal indexing process.</para>
<para>Unfortunately, using the <literal>-z</literal> option to
<command>recollindex</command> is not sufficient to change the
format, you have to delete all files inside the index
directory (typically <filename>~/.recoll/xapiandb</filename>)
before starting indexing.</para>
</sect2>
<sect2 id="rcl.indexing.storage.security">
<title>Security aspects</title>
<para>The &RCL; index does not hold copies of the indexed
documents. But it does hold enough data to allow for an almost
complete reconstruction. If confidential data is indexed,
access to the database directory should be restricted. </para>
<para>As of version 1.4, &RCL; will create the configuration
directory with a mode of 0700 (access by owner only). As the
index data directory is by default a sub-directory of the
configuration directory, this should result in appropriate
protection.</para>
<para>If you use another setup, you should think of the kind
of protection you need for your index, and set the directory
and files access modes appropriately.</para>
</sect2>
</sect1>
<sect1 id="rcl.indexing.config">
<title>The indexing configuration</title>
<para>You can control which areas of the file system are
indexed, and how files are processed, by setting variables inside
the <link linkend="rcl.install.config">&RCL; configuration
files</link>.</para>
<para>You can also use <link linkend="rcl.search.multidb">multiple
indexes</link> defined by separate configurations, typically to
separate personal and shared indexes, or to take advantage of
the organization of your data to improve search precision.</para>
<para>The first time you start <command>recoll</command>, you
will be asked whether or not you would like recoll to build the
index. If you want to adjust the configuration before indexing,
just click <guilabel>Cancel</guilabel> at this point. That way,
recoll will have created a ~/.recoll directory containing empty
configuration files.</para>
<para>The configuration is documented inside the <link
linkend="rcl.install.config">installation chapter</link> of this
document, or in the recoll.conf(5) man page, but the most
current information will most likely be the comments inside the
sample file. The most immediately useful variable you may
interested in is probably <link
linkend="rcl.install.config.recollconf.topdirs">topdirs</link>,
which determines what subtrees get indexed.</para>
<para>The applications needed to index file types other than
text, HTML or email (ie: pdf, postscript, ms-word...) are
described in the <link linkend="rcl.install.external">external
packages section</link></para>
</sect1>
<sect1 id="rcl.indexing.periodic">
<title>Periodic indexing</title>
<sect2 id="rcl.indexing.periodic.exec">
<title>Starting indexing</title>
<para>Indexing is performed either by the
<command>recollindex</command> program, or by the
indexing thread inside the <command>recoll</command>
program (use the <guimenu>File</guimenu> menu). Both programs
will use of the <literal>RECOLL_CONFDIR</literal>
variable or accept a <literal>-c</literal>
<replaceable>confdir</replaceable> option to specify the
configuration directory to be used.</para>
<para>If the <command>recoll</command> program finds no index
when it starts, it will automatically start indexing (except
if canceled).</para>
<para>It is best to avoid interrupting the indexing process, as
this may sometimes leave the index in a bad state. This is
not a serious problem, as you then just need to delete
the index files and restart the indexing. The index files are
normally stored in the <filename>$HOME/.recoll/xapiandb</filename>
directory, which you can just delete if needed. Alternatively,
you can start <command>recollindex</command> with option
<literal>-z</literal>, which will reset the database before
indexing.</para>
</sect2>
<sect2 id="rcl.indexing.periodic.automat">
<title>Using <command>cron</command> to automate
indexing</title>
<para>The most common way to set up indexing is to have a cron
task execute it every night. For example the following
<filename>crontab</filename> entry would do it every day at
3:30AM (supposing <command>recollindex</command> is in your PATH):</para>
<programlisting>30 3 * * * recollindex > /tmp/recolltrace 2>&1</programlisting>
<para>The usual command to edit your
<filename>crontab</filename> is
<userinput>crontab -e</userinput> (which will usually start the
<command>vi</command> editor to edit the file). You may have
more sophisticated tools available on your system.</para>
</sect2>
</sect1>
<sect1 id="rcl.indexing.monitor">
<title>Real time indexing</title>
<para>Real time monitoring/indexing is performed by starting the
<command>recollindex -m</command> command. With this option,
<command>recollindex</command> will detach from the terminal and
become a daemon, permanently monitoring file changes and updating
the index.</para>
<para>The real time indexing support can be customised during package
<link linkend="rcl.install.building.build">configuration</link>
with the <literal>--with[out]-fam</literal> or
<literal>--with[out]-inotify</literal> options. The default is
currently to include inotify monitoring on systems that support
it.</para>
<para>The <filename>rclmon.sh</filename> script can be used to
easily start and stop the daemon. It can be found in the
<filename>examples</filename> directory (typically
<filename>/usr/local/[share/]recoll/examples</filename>).</para>
<para>Starting the daemon is normally performed as part
of the user session script. For example, my out of fashion
xdm-based session has a <filename>.xsession</filename> script
with the following lines at the end:</para>
<programlisting>recollconf=$HOME/.recoll-home
recolldata=/usr/local/share/recoll
RECOLL_CONFDIR=$recollconf $recolldata/examples/rclmon.sh start
fvwm
</programlisting>
<para>The indexing daemon gets started, then the window manager,
for which the session waits.</para> <para>By default the
indexing daemon will monitor the state of the X11 session, and
exit when it finishes, it is not necessary to kill it
explicitely. (The X11 server monitoring can be disabled with option
<literal>-x</literal> to <command>recollindex</command>).
</para>
<para>Under KDE, you can place a small script to start
<command>recollindex -m</command> under
<filename>$HOME/.kde/Autostart</filename>. This will be executed
when the session begins.</para>
<para>There is a similar mechanism under Gnome (find the session
control tool in the menus and use the "Startup programs" tab).</para>
<para>By default, the indexing daemon will write its messages to
a file inside the configuration directory (this is controlled by
the <literal>daemlogfilename</literal> and
<literal>daemloglevel</literal> configuration parameters). You
may want to change this. Also the log file will only be truncated
when the daemon starts. If the daemon runs permanently, the log
file may grow quite big, depending on the log level.</para>
<para>While it is convenient that data is indexed in real time,
repeated indexing can generate a significant load on the system
when files such as email folders change. You probably do not
want to enable it if your system is short on resources. Periodic
indexing is adequate in most cases.</para>
</sect1>
</chapter>
<chapter id="rcl.search">
<title>Searching</title>
<para>The <command>recoll</command> program provides the user
interface for searching. It is based on the
<application>QT</application> library.</para>
<sect1 id="rcl.search.simple">
<title>Simple search</title>
<procedure>
<step><para>Start the <command>recoll</command> program.</para>
</step>
<step><para>Possibly choose a search mode: <guilabel>Any
term</guilabel> or <guilabel>All terms</guilabel> or
<guilabel>File name</guilabel>.</para>
</step>
<step><para>Enter search term(s) in the text field at the top of the
window.</para>
</step>
<step><para>Click the <guilabel>Search</guilabel> button or
hit the <keycap>Enter</keycap> key to start the search.</para>
</step>
</procedure>
<para>The initial default search mode is <guilabel>All
terms</guilabel>. This will look for documents containing all
of the search terms (the ones with more terms will get better
scores). <guilabel>Any term</guilabel> will search for
documents where at least one of the terms appear. <guilabel>File
name</guilabel> will specifically look for file names.</para>
<para>The fourth entry (<guilabel>Query Language</guilabel>) is
described in <link linkend="rcl.search.lang">its own
section</link>.</para>
<para>All search modes allow wildcards inside terms
(<literal>*</literal>, <literal>?</literal>,
<literal>[]</literal>). You may want to have a look at the
<link linkend="rcl.search.wildcards">section about wildcards</link>
for more information about this.</para>
<para>You can search for exact phrases (adjacent words in a
given order) by enclosing the input inside double quotes. Ex:
<literal>"virtual reality"</literal>.</para>
<para>Character case has no influence on search, except that you
can disable stem expansion for any term by capitalizing it. Ie:
a search for <literal>floor</literal> will also normally look for
<literal>flooring</literal>, <literal>floored</literal>, etc., but
a search for <literal>Floor</literal> will only look for
<literal>floor</literal>, in any character case (stemming can
also be disabled globally in the preferences). </para>
<para>&RCL; remembers the last few searches that you
performed. You can use the simple search text entry widget (a
combobox) to recall them (click on the thing at the right of the
text field). Please note, however, that only the search texts
are remembered, not the mode (all/any/file name).</para>
<para>Typing <keycap>Esc</keycap> <keycap>Space</keycap> while
entering a word in the simple search entry will open a window
with possible completions for the word. The completions are
extracted from the database.</para>
<para>Double-clicking on a word in the result list or a preview
window will insert it into the simple search entry field.</para>
<para>Note that, apart from wildcard characters (single
<literal>?</literal> characters are ok), you can cut and paste
any text into an <guilabel>All terms</guilabel> or
<guilabel>Any term</guilabel> search field, punctuation,
newlines and all. &RCL; will process it and produce a meaningful
search. This is what most differentiates this mode from the
<guilabel>Query Language</guilabel> mode, where you have to care
about the syntax.</para>
<para>You can use the <guilabel>Tools</guilabel> / <guilabel>Advanced
search</guilabel> dialog for more complex searches.</para>
</sect1>
<sect1 id="rcl.search.reslist">
<title>The result list</title>
<para>After starting a search, a list of results will instantly
be displayed in the main list window.</para>
<para>By default, the document list is presented in order of
relevance (how well the system estimates that the document
matches the query). You can specify a different ordering by
using the <link linkend="rcl.search.sort"><guilabel>Tools</guilabel>
/ <guilabel>Sort parameters</guilabel></link> dialog.</para>
<para>Clicking on the
<literal>Preview</literal> link for an entry will open an
internal preview window for the document. Further
<literal>Preview</literal> clicks for the same search will open
tabs in the existing preview window. You can use
<keycap>Shift</keycap>+Click to force the creation of another
preview window, which may be useful to view the documents side
by side. (You can also browse successive results in a single
preview window by typing
<keycap>Shift</keycap>+<keycap>ArrowUp/Down</keycap> in the
window).</para>
<para>Clicking the <literal>Edit</literal> link will attempt to
start an external viewer. The viewers can be configured through the
user preferences dialog, or by editing the
<filename>mimeview</filename> configuration file.</para>
<para>The <literal>Preview</literal> and <literal>Edit</literal>
edit links may not be present for all entries, meaning that
&RCL; has no configured way to preview a given file type (which
was indexed by name only), or no configured external viewer for
the file type. This can sometimes be adjusted simply by tweaking
the <link linkend="rclinstall.config.mimemap">
<filename>mimemap</filename></link> and
<link linkend="rclinstall.config.mimeview">
<filename>mimeview</filename></link> configuration files (the latter
can be modified with the user preferences dialog).</para>
<para>You can click on the <literal>Query details</literal> link
at the top of the results page to see the query actually
performed, after stem expansion and other processing.</para>
<para>Double-clicking on any word inside the result list or a
preview window will insert it into the simple search text.</para>
<para>The result list is divided into pages (the size of which
you can change in the preferences). Use the arrow buttons in the
toolbar or the links at the bottom of the page to browse the
results.</para>
<sect2 id="rcl.search.resultlist.menu">
<title>The result list right-click menu</title>
<para>Apart from the preview and edit links, you can display a
pop-up menu by right-clicking over a paragraph in the result
list. This menu has the following entries:</para>
<itemizedlist>
<listitem><para><guilabel>Preview</guilabel></para></listitem>
<listitem><para><guilabel>Edit</guilabel></para></listitem>
<listitem><para><guilabel>Copy File Name</guilabel></para></listitem>
<listitem><para><guilabel>Copy Url</guilabel></para></listitem>
<listitem><para><guilabel>Find similar</guilabel></para></listitem>
<listitem><para><guilabel>Find similar</guilabel></para></listitem>
<listitem><para><guilabel>Parent document</guilabel></para></listitem>
</itemizedlist>
<para>The <guilabel>Preview</guilabel> and
<guilabel>Edit</guilabel> entries do the same thing as the
corresponding links.</para>
<para>The <guilabel>Copy File Name</guilabel> and
<guilabel>Copy Url</guilabel> copy the relevant data to the
clipboard, for later pasting.</para>
<para>The <guilabel>Find similar</guilabel> entry will select
a number of relevant term from the current document and enter
them into the simple search field. You can then start a simple
search, with a good chance of finding documents related to the
current result.</para>
<para>The <guilabel>Parent document</guilabel> entry will
appear for documents which are not actually files but are
part of, or attached to, a higher level document. This entry
is mainly useful for email attachments and permits viewing
the message to which the document is attached. Note that the
entry will also appear for an email which is part of an mbox
folder file, but that you can't actually visualize the
folder (there will be an error dialog if you try). &RCL; is
unfortunately not yet smart enough to disable the entry in
this case.</para>
</sect2>
</sect1>
<sect1 id="rcl.search.preview">
<title>The preview window</title>
<para>The preview window opens when you first click a
<literal>Preview</literal> link inside the result list.</para>
<para>Subsequent preview requests for a given search open new
tabs in the existing window (except if you hold the
<keycap>Shift</keycap> key while clicking which will open a new
window for side by side viewing).</para>
<para>Starting another search and requesting a preview will
create a new preview window. The old one stays open until you
close it.</para>
<para>You can close a preview tab by typing <keycap>^W</keycap>
(<keycap>Ctrl</keycap> + <keycap>W</keycap>) in the
window. Closing the last tab for a window will also close the
window.</para>
<para>Of course you can also close a preview window by using the
window manager button in the top of the frame.</para>
<para>You can display successive or previous documents from the
result list inside a preview tab by typing
<keycap>Shift</keycap>+<keycap>Down</keycap> or
<keycap>Shift</keycap>+<keycap>Up</keycap> (<keycap>Down</keycap>
and <keycap>Up</keycap> are the arrow keys).</para>
<para>The preview tabs have an internal incremental search
function. You initiate the search either by typing a
<keycap>/</keycap> (slash) inside the text area or by clicking
into the <guilabel>Search for:</guilabel> text field and
entering the search string. You can then use the
<guilabel>Next</guilabel> and <guilabel>Previous</guilabel>
buttons to find the next/previous occurrence. You can also type
<keycap>F3</keycap> inside the text area to get to the next
occurrence.</para>
<para>If you have a search string entered and you use ^Up/^Down
to browse the results, the search is initiated for each successive
document. If the string is found, the cursor will be positioned
at the first occurrence of the search string.</para>
</sect1>
<sect1 id="rcl.search.lang">
<title>The query language</title>
<para>The query language processor is activated on the
simple search entry when the search mode selector is set to
<guilabel>Query Language</guilabel>.</para>
<para>Here follows a sample request that we are going to
explain:</para>
<programlisting>
author:"john doe" Beatles OR Lennon Live OR Unplugged -potatoes
</programlisting>
<para>This would search for all documents with
<replaceable>John Doe</replaceable>
appearing as a phrase in the author field (exactly what this is
would depend on the document type, ie: the
<literal>From:</literal> header, for an email message),
and containing either <replaceable>beatles</replaceable> or
<replaceable>lennon</replaceable> and either
<replaceable>live</replaceable> or
<replaceable>unplugged</replaceable> but not
<replaceable>potatoes</replaceable> (in any part of the document).</para>
<para>All elements in the search entry are normally combined
with an implicit AND. It is possible to specify that elements be
OR'ed instead, as in <replaceable>Beatles</replaceable>
<literal>OR</literal> <replaceable>Lennon</replaceable>. The
<literal>OR</literal> must be entered literally (capitals), and
it has priority over the AND associations:
<replaceable>word1</replaceable>
<replaceable>word2</replaceable> <literal>OR</literal>
<replaceable>word3</replaceable>
means
<replaceable>word1</replaceable> AND
(<replaceable>word2</replaceable> <literal>OR</literal>
<replaceable>word3</replaceable>)
not
(<replaceable>word1</replaceable> AND
<replaceable>word2</replaceable>) <literal>OR</literal>
<replaceable>word3</replaceable>. Do not enter explicit
parenthesis, they are not supported for now.</para>
<para>An entry preceded by a <literal>-</literal> specifies a
term that should <emphasis>not</emphasis> appear.</para>
<para>The first element in the above exemple,
<literal>author:"john doe"</literal> is a phrase search limited
to a specific field. Phrase searches are specified as usual by
enclosing the words in double quotes. The field specification
appears before the colon (of course this is not limited to
phrases, <literal>author:Balzac</literal> would be ok
too). &RCL; currently manages the following fields:</para>
<itemizedlist>
<listitem><para><literal>title</literal>,
<literal>subject</literal> or <literal>caption</literal> are
synonyms which specify data to be searched for in the
document title or subject.</para>
</listitem>
<listitem><para><literal>author</literal> or
<literal>from</literal> for searching the documents originators.</para>
</listitem>
<listitem><para><literal>keyword</literal> for searching the
document specified keywords (few documents actually have any).</para>
</listitem>
</itemizedlist>
<para>As of release 1.9, the filters have the possibility to
create other fields with arbitrary names. No standard filters
use this possibility yet.</para>
<para>There are two other elements which may be specified
through the field syntax, but are somewhat special:</para>
<itemizedlist>
<listitem><para><literal>ext</literal> for specifying the file
name extension (Ex: <literal>ext:html</literal>)</para>
</listitem>
<listitem><para><literal>mime</literal> for specifying the
mime type. This one is quite special because you can specify
several values which will be OR'ed (the normal default for the
language is AND). Ex: <literal>mime:text/plain
mime:text/html</literal>. Specifying an explicit boolean
operator or negation (<literal>-</literal>) before a
<literal>mime</literal> specification is not supported and
will produce strange results.</para>
</listitem>
</itemizedlist>
<para>The query language is currently the only way to use the
&RCL; field search capability.</para>
<para>Words inside phrases and capitalized words are not
stem-expanded. Wildcards may be used anywhere inside a term.
Specifying a wild-card on the left of a term can produce a very
slow search.</para>
<para>You can use the <literal>show query</literal> link at the
top of the result list to check the exact query which was
finally executed by Xapian.</para>
</sect1>
<sect1 id="rcl.search.complex">
<title>Complex/advanced search</title>
<para>The advanced search dialog has a number of fields that
will allow a more refined search. Each entry field is
configurable for the following modes:</para>
<itemizedlist>
<listitem><para>All terms.</para>
</listitem>
<listitem><para>Any term.</para>
</listitem>
<listitem><para>None of the terms.</para>
</listitem>
<listitem><para>Phrase (exact terms in order within an
adjustable window).</para>
</listitem>
<listitem><para>Proximity (terms in any order within an
adjustable window).</para>
</listitem>
<listitem><para>Filename search with wildcards.</para>
</listitem>
</itemizedlist>
<para>Additional entry fields can be created by clicking the
<guilabel>Add clause</guilabel> button.</para>
<para>You can choose that all relevant fields will be combined
by either an AND or an OR conjunction. All types of clauses
except "phrase" and "near" can accept a mix of single words and
phrases enclosed in double quotes. Stemming expansion will be
performed for all terms not beginning with a capital letter,
except for terms inside "phrase" clauses. Wildcards will be
processed everywhere.</para>
<para>Advanced search will also let you search for documents of
specific mime types (ie: only <literal>text/plain</literal>, or
<literal>text/HTML</literal> or
<literal>application/pdf</literal> etc...). The state of the
file type selection can be saved as the default (the file type
filter will not be activated at program start-up, but the lists
will be in the restored state).</para>
<para>You can also restrict the search results
to a sub-tree of the indexed area. If you need to do this often,
you may think of setting up multiple indexes instead, as the
performance will be much better.</para>
<para>Click on the <guilabel>Start Search</guilabel> button in
the advanced search dialog, or type <keycap>Enter</keycap> in
any text field to start the search. The button in
the main window always performs a simple search.</para>
<para>Click on the <literal>Show query details</literal> link at
the top of the result page to see the query expansion.</para>
</sect1>
<sect1 id="rcl.search.termexplorer">
<title>The term explorer tool</title>
<para>&RCL; automatically manages the expansion of search terms
to their derivatives (ie: plural/singular, verb
inflections). But there are other cases where the exact search
term is not known. For example, you may not remember the exact
spelling, or only know the beginning of the name.</para>
<para>The term explorer tool (started from the toolbar icon or
from the <guilabel>Term explorer</guilabel> entry of the
<guilabel>Tools</guilabel> menu) can be used to search the full index
terms list. It has three modes of operations:</para>
<variablelist>
<varlistentry>
<term>Wildcard</term>
<listitem><para>In this mode of operation, you can enter a
search string with shell-like wildcards (*, ?, []). ie:
<replaceable>xapi*</replaceable> would display all index terms
beginning with <replaceable>xapi</replaceable>. (More
about wildcards <link
linkend="rcl.search.wildcards">here</link>).</para></listitem>
</varlistentry>
<varlistentry>
<term>Regular expression</term>
<listitem><para>This mode will accept a regular expression
as input. Example:
<replaceable>word[0-9]+</replaceable>. The expression is
implicitely anchored at the beginning. Ie:
<replaceable>press</replaceable> will match
<replaceable>pression</replaceable> but not
<replaceable>expression</replaceable>. You can use
<replaceable>.*press</replaceable> to match the latter,
but be aware that this will cause a full index term list
scan, which can be quite long.</para>
</listitem>
</varlistentry>
<varlistentry>
<term>Stem expansion</term>
<listitem><para>This mode will perform the usual stem expansion
normally done as part user input processing. As such it is
probably mostly useful to demonstrate the process.
</para></listitem>
</varlistentry>
<varlistentry>
<term>Spelling/Phonetic</term> <listitem><para>In this
mode, you enter the term as you think it is spelled, and
&RCL; will do its best to find index terms that sound like
your entry. This mode uses the
<application>Aspell</application> spelling application,
which must be installed on your system for things to work
(if your documents contain non-ascii characters, &RCL;
needs an aspell version newer than 0.60 for UTF-8
support). The language which is used to build the
dictionary out of the index terms (which is done at the
end of an indexing pass) is the one defined by your NLS
environment. Weird things will probably happen if
languages are mixed up.</para></listitem>
</varlistentry>
</variablelist>
<para>Note that in cases where &RCL; does not know the beginning
of the string to search for (ie a wildcard expression like
<replaceable>*coll</replaceable>), the expansion can take quite
a long time because the full index term list will have to be
processed. The expansion is currently limited at 200 results for
wildcards and regular expressions.</para>
<para>Double-clicking on a term in the result list will insert
it into the simple search entry field. You can also cut/paste
between the result list and any entry field (the end of lines
will be taken care of).</para>
</sect1>
<sect1 id="rcl.search.wildcards">
<title>More about wildcards</title>
<para>All words entered in &RCL; search fields will be processed
for wildcard expansion before the request is finally
executed.</para>
<para>The wildcard characters are:</para>
<itemizedlist>
<listitem><para><literal>*</literal> which matches 0 or more
characters.</para>
</listitem>
<listitem><para><literal>?</literal> which matches
a single character.</para>
</listitem>
<listitem><para><literal>[]</literal> which allow
defining sets of characters to be matched (ex:
<literal>[</literal><userinput>abc</userinput><literal>]</literal>
matches a single character which may be 'a' or 'b' or 'c',
<literal>[</literal><userinput>0-9</userinput><literal>]</literal>
matches any number.</para>
</listitem>
</itemizedlist>
<para>You should be aware of a few things before using
wildcards.</para>
<itemizedlist>
<listitem><para>Using a wildcard character at the beginning of
a word can make for a slow search because &RCL; will have to
scan the whole index term list to find the matches.</para>
</listitem>
<listitem><para>Using a <literal>*</literal> at the end of a
word can produce more matches than you would think, and
strange search results. You can use the <link
linkend="rcl.search.termexplorer">term explorer</link> tool to
check what completions exist for a given term. You can also
see exactly what search was performed by clicking on the link
at the top of the result list. In general, for natural
language terms, stem expansion will produce better results
than an ending <literal>*</literal> (stem expansion is turned
off when any wildcard character appears in the term).</para>
</listitem>
</itemizedlist>
</sect1>
<sect1 id="rcl.search.multidb">
<title>Multiple databases</title>
<para>Multiple &RCL; databases or indexes can be created by
using several configuration directories which are usually set to
index different areas of the file system. A specific index can
be selected for updating or searching, using the
<literal>RECOLL_CONFDIR</literal> environment variable or the
<literal>-c</literal> option to <command>recoll</command> and
<command>recollindex</command>.</para>
<para>A <command>recollindex</command> program instance can only
update one specific index.</para>
<para>A <command>recoll</command> program instance is also
associated with a specific index, which is the one to be
updated by its indexing thread, but it can use any
number of &RCL; indexes for searching. The external indexes
can be selected through the <guilabel>external
indexes</guilabel> tab in the preferences dialog.</para>
<para>Index selection is performed in two phases. A set of all
usable indexes must first be defined, and then the subset of
indexes to be used for searching. Of course, these parameters
are retained across program executions (there are kept
separately for each &RCL; configuration). The set of all indexes
is usually quite stable, while the active ones might typically
be adjusted quite frequently.</para>
<para>The main index (defined by
<literal>RECOLL_CONFDIR</literal>) is always active. If this is
undesirable, you can set up your base configuration to index
an empty directory.</para>
<para>As building the set of all indexes can be a little tedious
when done through the user interface, you can use the
<literal>RECOLL_EXTRA_DBS</literal> environment
variable to provide an initial set. This might typically be
set up by a system administrator so that every user does not
have to do it. The variable should define a colon-separated list
of index directories, ie:
</para>
<screen>export RECOLL_EXTRA_DBS=/some/place/xapiandb:/some/other/db</screen>
<para>A typical usage scenario for the multiple index feature
would be for a system administrator to set up a central index
for shared data, that you choose to search or not in addition to
your personal data. Of course, there are other
possibilities. There are many cases where you know the subset of
files that should be searched, and where narrowing the search
can improve the results. You can achieve approximately the same
effect with the directory filter in advanced search, but
multiple indexes will have much better performance and may be
worth the trouble.</para>
</sect1>
<sect1 id="rcl.search.history">
<title>Document history</title>
<para>Documents that you actually view (with the internal preview
or an external tool) are entered into the document history,
which is remembered.</para>
<para>You can display the history list by using
the <guilabel>Tools/</guilabel><guilabel>Doc History</guilabel> menu
entry.</para>
<para>You can erase the document history by using the
<guilabel>Erase document history</guilabel> entry in the
<guimenu>File</guimenu> menu.
</sect1>
<sect1 id="rcl.search.sort">
<title>Sorting search results</title>
<para>The documents in a result list are normally sorted in
order of relevance. It is possible to specify different sort
parameters by using the <guimenu>Sort parameters</guimenu>
dialog (located in the <guimenu>Tools</guimenu>
menu).</para>
<para>The tool sorts a specified number of the most
relevant documents in the result list, according to
specified criteria. The currently available criteria are
<emphasis>date</emphasis> and <emphasis>mime type</emphasis>.</para>
<para>The sort parameters stay in effect until they are explicitly
reset, or the program exits. An activated sort is indicated in
the result list header.</para>
<para>Sort parameters are remembered between program
invocations, but result sorting is normally always inactive when
the program starts. It is possible to keep the sorting
activation state between program invocations by checking the
<guilabel>Remember sort activation state</guilabel>
option in the preferences.</para>
</sect1>
<sect1 id="rcl.search.tips">
<title>Search tips, shortcuts</title>
<formalpara><title>Term completion</title>
<para>Typing <keycap>Esc</keycap> <keycap>Space</keycap> in
the simple search entry field while entering a word will
either complete the current word if its beginning matches a
unique term in the index, or open a window to propose a list
of completions.</para>
</formalpara>
<formalpara><title>Picking up new terms from result or preview
text</title>
<para>Double-clicking on a word in the result list or in a
preview window will copy it to the simple search entry field.</para>
</formalpara>
<formalpara><title>Disabling stem expansion</title>
<para>Entering a capitalized word in any search field will prevent
stem expansion (no search for
<literal>gardening</literal> if you enter
<literal>Garden</literal> instead of
<literal>garden</literal>). This is the only case where
character case should make a difference for a &RCL;
search. You can also disable stem expansion or change the
stemming language in the preferences.</para>
</formalpara>
<formalpara><title>Phrases</title>
<para>A phrase can be looked for by enclosing it in double
quotes. Example: <literal>"user manual"</literal> will look
only for occurrences of <literal>user</literal> immediately
followed by <literal>manual</literal>. You can use the
<guilabel>This exact phrase</guilabel> field of the advanced
search dialog to the same effect. Phrases can be entered along
simple terms in all simple or advanced search entry fields
(except <guilabel>This exact phrase</guilabel>).</para>
</formalpara>
<formalpara><title>Browsing the result list inside a preview
window (1.5)</title>
<para>Entering <keycap>Shift-Down</keycap> or <keycap>Shift-Up</keycap>
(<keycap>Shift</keycap> + an arrow key) in a preview window will
display the next or the previous document from the result
list. Any secondary search currently active will be executed on
the new document.</para>
</formalpara>
<formalpara><title>Forced opening of a preview window (1.6)</title>
<para>You can use <keycap>Shift</keycap>+Click on a result list
<literal>Preview</literal> link to force the creation of a
preview window instead of a new tab in the existing one.</para>
</formalpara>
<formalpara><title>AutoPhrases (1.5)</title>
<para>This option can be set in the preferences dialog. If it is
set, a phrase will be automatically built and added to simple
searches when looking for <literal>Any terms</literal>. This
will not change radically the results, but will give a relevance
boost to the results where the search terms appear as a
phrase. Ie: searching for <literal>virtual reality</literal>
will still find all documents where either
<literal>virtual</literal> or <literal>reality</literal> or
both appear, but those which contain <literal>virtual
reality</literal> should appear sooner in the list.</para>
<formalpara><title>Finding related documents</title>
<para>Selecting the <guilabel>Find similar documents</guilabel> entry
in the result list paragraph right-click menu will select a
set of "interesting" terms from the current result, and insert
them into the simple search entry field. You can then possibly
edit the list and start a search to find documents which may
be apparented to the current result.</para>
</formalpara>
<formalpara><title>File names</title>
<para>File names are added as terms during indexing, and you can
specify them as ordinary terms in normal search fields (&RCL; used
to index all directories in the file path as terms. This has been
abandoned as it did not seem really useful). Alternatively, you
can use the specific file name search which will
<emphasis>only</emphasis> look for file names and can use wildcard
expansion.</para>
</formalpara>
<formalpara><title>Query explanation</title>
<para>You can get an exact description of what the query
looked for, including stem expansion, and Boolean operators
used, by clicking on the result list header.</para>
</formalpara>
<formalpara><title>Closing previews</title>
<para>Entering <keycap>^W</keycap> in a tab will
close it (and, for the last tab, close the preview
window). Entering <keycap>Esc</keycap> will close the preview
window and all its tabs.</para>
</formalpara>
<formalpara><title>Quitting</title>
<para>Entering <keycap>^Q</keycap> almost anywhere will
close the application.</para>
</formalpara>
</sect1>
<sect1 id="rcl.search.custom">
<title>Customizing the search interface</title>
<para>It is possible to customize some aspects of the search
interface by using <guimenu>Query configuration</guimenu> entry
in the <guimenu>Preferences</guimenu> menu.</para>
<para>There are two tabs in the dialog, dealing with the
interface itself, and with the parameters used for searching and
returning results.</para>
<formalpara><title>User interface parameters:</title>
<para>
<itemizedlist>
<listitem><para><guilabel>Number of results in a result
page</guilabel></para>
</listitem>
<listitem><para><guilabel>Result list font</guilabel>: There
is quite a lot of information shown in the result list, and
you may want to customize the font and/or font size. The rest
of the fonts used by &RCL; are determined by your generic QT
config (try the <command>qtconfig</command> command.</para>
</listitem>
<listitem><para><guilabel>Result paragraph format
string</guilabel>: allows you to change the presentation of
each result list entry. This is a qt-html string where the
following printf-like <literal>%</literal> substitutions will
be performed:
<itemizedlist>
<listitem>
<formalpara><title>%A</title><para>Abstract</para></formalpara>
</listitem>
<listitem><formalpara><title>%D</title><para>Date</para></formalpara>
</listitem>
<listitem><formalpara><title>%I</title><para>Icon image name
</para></formalpara>
</listitem>
<listitem><formalpara><title>%K</title><para>Keywords (if
any)</para></formalpara>
</listitem>
<listitem><formalpara><title>%L</title><para>Preview and
Edit links</para></formalpara>
</listitem>
<listitem><formalpara><title>%M</title><para>Mime
type</para></formalpara>
</listitem>
<listitem><formalpara><title>%N</title><para>result Number
</para></formalpara>
</listitem>
<listitem><formalpara><title>%R</title><para>Relevance
percentage</para></formalpara>
</listitem>
<listitem><formalpara><title>%S</title><para>Size
information</para></formalpara>
</listitem>
<listitem><formalpara><title>%T</title><para>Title</para>
</formalpara>
</listitem>
<listitem><formalpara><title>%U</title><para>Url</para></formalpara>
</listitem>
</itemizedlist>
The default value for the string is:
<programlisting><img src="%I" align="left">%R %S %L &nbsp;&nbsp;<b>%T</b><br>
%M&nbsp;%D&nbsp;&nbsp;&nbsp;<i>%U</i><br>
%A %K
</programlisting>
You may, for example, try the following for a more web-like
experience:
<programlisting><u><b><a href="P%N">%T</a></b></u><br>
%A<font color=#008000>%U - %S</font> - %L
</programlisting>
Or the clean looking:
<programlisting><img src="%I" align="left">%L <font color="#900000">%R</font>
<b>%T</b><br>%S
<font color="#808080"><i>%U</i></font>
<table bgcolor="#e0e0e0">
<tr><td><div>%A</div></td></tr>
</table>%K
</programlisting>
The format of the Preview and Edit links is
<literal><a href="P<replaceable>docnum</replaceable>"></literal>
and
<literal><a href="E<replaceable>docnum</replaceable>"></literal>
where <replaceable>docnum</replaceable> is what %N would
print. This makes the title a preview link in the above format.
</para>
<para>Please note that, due to the way the program
handles right mouse clicks in the result list, if the custom
formatting results in multiple paragraphs per result, right
clicks will only work inside the first one.</para>
</listitem>
<listitem><para><guilabel>HTML help browser</guilabel>: this
will let you chose your preferred browser which will be
started from the <guimenu>Help</guimenu> menu to read the user
manual. You can enter a simple name if the command is in your
PATH, or browse for a full pathname.</para>
</listitem>
<listitem><para><guilabel>Auto-start simple search on
white space entry</guilabel>: if this is checked, a search will
be executed each time you enter a space in the simple search
input field. This lets you look at the result list as you
enter new terms. This is off by default, you may like it or
not...</para>
</listitem>
<listitem><para><guilabel>Start with advanced search dialog open
</guilabel> and <guilabel>Start with sort dialog open</guilabel>:
If you use these dialogs all the time, checking these
entries will get them to open when recoll starts.</para>
</listitem>
<listitem><para><guilabel>Use desktop preferences to choose
document editor</guilabel>: if this is checked, the
<command>xdg-open</command>
utility will be used to open files when you click the
<guilabel>Edit</guilabel> link in the result list, instead of
the application defined in
<filename>mimeview</filename>. <command>xdg-open</command>
will in term use your desktop preferences to choose an
appropriate application.</para>
</listitem>
</itemizedlist>
</para>
</formalpara>
<formalpara><title>Search parameters:</title>
<para>
<itemizedlist>
<listitem><para><guilabel>Stemming language</guilabel>:
stemming obviously depends on the document's language. This
listbox will let you chose among the stemming databases which
were built during indexing (this is set in the <link
linkend="rcl.install.config.recollconf">main configuration
file</link>), or later added with
<command>recollindex -s</command> (See the recollindex
manual). Stemming languages which are dynamically added will be
deleted at the next indexing pass unless they are also added in
the configuration file.</para>
</listitem>
<listitem><para><guilabel>Dynamically build
abstracts</guilabel>: this decides if &RCL; tries to build
document abstracts when displaying the result list. Abstracts
are constructed by taking context from the document
information, around the search terms. This can slow down
result list display significantly for big documents, and you
may want to turn it off.</para>
</listitem>
<listitem><para><guilabel>Replace abstracts from
documents</guilabel>: this decides if we should synthesize and
display an abstract in place of an explicit abstract found
within the document itself.</para>
</listitem>
<listitem><para><guilabel>Synthetic abstract size</guilabel>:
adjust to taste...</para>
</listitem>
<listitem><para><guilabel>Synthetic abstract context
words</guilabel>: how many words should be displayed around
each term occurrence.</para>
</listitem>
</itemizedlist>
</para>
</formalpara>
<formalpara id="rcl.search.custom.extradb">
<title>External indexes:</title>
<para>This panel will let you browse for additional indexes
that you may want to search. External indexes are designated by
their database directory (ie:
<filename>/home/someothergui/.recoll/xapiandb</filename>,
<filename>/usr/local/recollglobal/xapiandb</filename>).</para>
<para>Once entered, the indexes will appear in the
<guilabel>External indexes</guilabel> list, and you can
chose which ones you want to use at any moment by checking or
unchecking their entries.</para>
<para>Your main database (the one the current configuration
indexes to), is always implicitly active. If this is not
desirable, you can set up your configuration so that it indexes,
for example, an empty directory.</para>
</sect1>
</chapter>
<chapter id="rcl.install">
<title>Installation</title>
<sect1 id="rcl.install.binary">
<title>Installing a prebuilt copy</title>
<para>&RCL; binary packages from the &RCL; web site are always
linked statically to the &XAP; libraries, and have no other
dependencies. You will only have to check or install <link
linkend="rcl.install.external">supporting applications</link>
for the file types that you want to index beyond text, HTML and
mail files, and maybe have a look at the
<link linkend="rcl.install.config">configuration section</link>
(but this may not be necessary for a quick test with default
parameters).</para>
<sect2 id="rcl.install.binary.package">
<title>Installing through a package system</title>
<para>If you use a BSD-type port system or a prebuilt package
(RPM or other), just follow the usual procedure for your
system.</para>
</sect2>
<sect2 id="rcl.install.binary.rcl">
<title>Installing a prebuilt &RCL;</title>
<para>The unpackaged binary versions on the &RCL; web site are
just compressed tar files of a build tree, where only the
useful parts were kept (executables and sample
configuration).</para>
<para>The executable binary files are built with a static link to
libxapian and libiconv, to make installation easier (no
dependencies).</para>
<para>After extracting the tar file, you can proceed with
<link linkend="rcl.install.building.install">installation</link> as
if you had built the package from source (that is, just type
<literal>make install</literal>). The binary trees are built for
installation to <filename>/usr/local</filename>.</para>
</sect2>
</sect1>
<sect1 id="rcl.install.external">
<title>Supporting packages</title>
<para>&RCL; uses external applications to index some file
types. You need to install them for the file types that you wish to
have indexed (these are run-time dependencies. None is needed for
building &RCL;):</para>
<itemizedlist>
<listitem><para>Openoffice: supported natively, but needs the
<command>unzip</command> command to be installed.</para>
</listitem>
<listitem><para>PDF: pdftotext is part of the <ulink
url="http://www.foolabs.com/xpdf/">Xpdf</ulink> package.</para>
</listitem>
<listitem><para>Postscript: <ulink
url="http://www.cs.wisc.edu/~ghost/doc/pstotext.htm">
pstotext</ulink>.</para>
</listitem>
<listitem><para>MS Word: <ulink url="http://www.winfield.demon.nl">
antiword</ulink>.</para>
</listitem>
<listitem><para>MS Excel and PowerPoint:
<ulink url="http://www.45.free.net/~vitus/software/catdoc/">
catdoc</ulink>.</para>
</listitem>
<listitem><para>Wordperfect files:
<ulink url="http://libwpd.sourceforge.net/download.html">
libwpd</ulink>.</para>
</listitem>
<listitem>
<para>RTF: <ulink
url="http://www.gnu.org/software/unrtf/unrtf.html">unrtf</ulink>
</para>
</listitem>
<listitem>
<para>dvi: <ulink
url="http://www.radicaleye.com/dvips.html">dvips</ulink></para>
</listitem>
<listitem>
<para>djvu:
<ulink
url="http://djvulibre.djvuzone.org/doc/index.html">DjVuLibre
</ulink></para>
</listitem>
<listitem><para>MP3: &RCL; will use the
<command>id3info</command> command from the <ulink
url="http://id3lib.sourceforge.net/">id3lib</ulink> package to
extract tag information. Without it, only the file names will
be indexed.</para>
</listitem>
</itemizedlist>
<para>Text, HTML, mail folders Openoffice and Scribus files
are processed internally. Lyx is used to index Lyx files. Many
filters need <command>sed</command> and <command>awk</command>.
</para>
</sect1>
<sect1 id="rcl.install.building">
<title>Building from source</title>
<sect2 id="rcl.install.building.prereqs">
<title>Prerequisites</title>
<para>At the very least, you will need to download and install the
<ulink url="http://www.xapian.org">xapian core package</ulink>
(&RCL; 1.9 normally uses version 1.0.2, but any 0.9 or 1.0.x
version will work too), and the <ulink
url="http://www.trolltech.com/products/qt/index.html">qt
run-time and development packages</ulink> (&RCL; development
currently uses version 3.3.5, but any 3.3 version is
probably OK).</para>
<para>You will most probably be able to find a binary package for
<application>qt</application> for your system. You may have to
compile &XAP; but this is not difficult (if you are using
<application>FreeBSD</application>, there is a port).</para>
<para>You may also need
<ulink
url="http://www.gnu.org/software/libiconv/">libiconv</ulink>. &RCL;
currently uses version 1.9 (this should not be critical). On
<application>Linux</application> systems, the iconv interface
is part of libc and you should not need to do anything
special.</para>
<sect2 id="rcl.install.building.build">
<title>Building</title>
<para>&RCL; has been built on
Linux (redhat7.3, mandriva 2005/6, Fedora Core 3/4/5/6),
FreeBSD 5/6, macosx, and Solaris 8. If you build on another system, and
need to modify things,
<ulink url="mailto:jean-francois.dockes@wanadoo.fr">I would
very much welcome patches</ulink>.</para>
<para>Depending on the <application>qt</application>
configuration on your system, you may have to set the
<literal>QTDIR</literal> and <literal>QMAKESPECS</literal>
variables in your environment:</para>
<itemizedlist>
<listitem><para><literal>QTDIR</literal> should point to the
directory above the one that holds the qt include files (ie:
if <filename>qt.h</filename> is
<filename>/usr/local/qt/include/qt.h</filename>, QTDIR
should be <filename>/usr/local/qt</filename>).</para>
</listitem>
<listitem><para><literal>QMAKESPECS</literal> should
be set to the name of one of the
<application>qt</application> mkspecs sub-directories (ie:
linux-g++).</para>
</listitem>
</itemizedlist>
<para>On many Linux systems, <literal>QTDIR</literal> is set
by the login scripts, and <literal>QMAKESPECS</literal> is not
needed because there is a <filename>default</filename> link in
<filename>mkspecs/</filename>.</para>
<formalpara><title>Configure
options:</title><para><literal>--without-aspell</literal>
will disable the code for phonetic matching of search
terms. <literal>--with-fam</literal> or
<literal>--with-inotify</literal> will enable the code for
real time indexing. Inotify support is enabled by default on
recent Linux systems.</para>
<para>Normal procedure:</para>
<screen>
<userinput>cd recoll-xxx</userinput>
<userinput>configure</userinput>
<userinput>make</userinput>
<userinput>(practices usual hardship-repelling invocations)</userinput>
</screen>
<para>There little auto-configuration. The
<command>configure</command> script will mainly link one of
the system-specific files in the <filename>mk</filename>
directory to <filename>mk/sysconf</filename>. If your system
is not known yet, it will tell you as much, and you may want
to manually copy and modify one of the existing files (the new
file name should be the output of <command>uname -s</command>).</para>
</sect2>
<sect2 id="rcl.install.building.install">
<title>Installation</title>
<para>Either type <userinput>make install</userinput> or execute
<userinput>recollinstall
<replaceable>prefix</replaceable></userinput>, in the root
of the source tree. This will copy the commands to
<filename><replaceable>prefix</replaceable>/bin</filename>
and the sample configuration files, scripts and other shared
data to
<filename><replaceable>prefix</replaceable>/share/recoll</filename>.</para>
<para>If the installation prefix given to
<command>recollinstall</command> is different from what was
specified when executing <command>configure</command>, you
will have to set the <literal>RECOLL_DATADIR</literal>
environment variable to indicate where the shared data is to
be found.</para>
<para>You can then proceed to <link
linkend="rcl.install.config">configuration</link>. </para>
</sect2>
</sect1>
<sect1 id="rcl.install.config">
<title>Configuration overview</title>
<para>Most of the parameters specific to the
<command>recoll</command> GUI are set through the
<guilabel>Preferences</guilabel> menu and stored in the
standard QT place
(<filename>$HOME/.qt/recollrc</filename>). You probably do not
want to edit this by hand.</para>
<para>For other options, &RCL; uses text configuration
files. You will have to edit them by hand for
now (there is still some hope for a GUI configuration tool
in the future). The most accurate documentation for the
configuration parameters is given by comments inside the default
files, and we will just give a general overview here.</para>
<para>There are two sets of configuration files. The system-wide
files are kept in a directory named like
<filename>/usr/[local/]share/recoll/examples</filename>,
they define default values for the system. A parallel set of
files exists by default in the <filename>.recoll</filename> directory
in your home. This directory can be changed with the
<literal>RECOLL_CONFDIR</literal> environment variable or the -c
option parameter to <command>recoll</command> and
<command>recollindex</command>.</para>
<para>If the <filename>.recoll</filename> directory does not
exist when <command>recoll</command> or
<command>recollindex</command> are started, it will be created
with a set of empty configuration files.
<command>recoll</command> will give you a chance to edit the
configuration file before starting
indexing. <command>recollindex</command> will proceed
immediately. To avoid mistakes, the automatic directory
creation will only occur for the
default location, not if <literal>-c</literal> or
<literal>RECOLL_CONFDIR</literal> were used (in the latter
cases, you will have to create the directory).</para>
<para>All configuration files share the same format. For
example, a short extract of the main configuration file might
look as follows:</para>
<programlisting>
# Space-separated list of directories to index.
topdirs = ~/docs /usr/share/doc
[~/somedirectory-with-utf8-txt-files]
defaultcharset = utf-8
</programlisting>
<para>There are three kinds of lines: </para>
<itemizedlist>
<listitem><para>Comment (starts with
<emphasis>#</emphasis>) or empty.</para>
</listitem>
<listitem><para>Parameter affectation (<emphasis>name =
value</emphasis>).</para>
</listitem>
<listitem><para>Section definition
([<emphasis>somedirname</emphasis>]).</para>
</listitem>
</itemizedlist>
<para>Section definitions allow redefining some parameters for
a directory sub-tree. They stay in effect until another
section definition, or the end of file, is encountered. Some
of the parameters used for indexing are looked up
hierarchically from the current directory location
upwards. Not all parameters can be meaningfully redefined,
this is specified for each in the next section. </para>
<para>When found at the beginning of a file path, the tilde
character (~) is expanded to the name of the user's home
directory, as a shell would do.</para>
<para>White space is used for separation inside lists.
List elements with embedded spaces can be quoted using
double-quotes.</para>
<sect2 id="rcl.install.config.recollconf">
<title>Main configuration file</title>
<para><filename>recoll.conf</filename> is the main
configuration file. It defines things like
what to index (top directories and things to ignore), and the
default character set to use for document types which do not
specify it internally.</para>
<para>The default configuration will index your home
directory. If this is not appropriate, start
<command>recoll</command> to create a blank
configuration, click <guimenu>Cancel</guimenu>, and edit
the configuration file before restarting the command. This
will start the initial indexing, which may take some time.</para>
<para>Paramers:</para>
<variablelist>
<varlistentry id="rcl.install.config.recollconf.topdirs">
<term><literal>topdirs</literal></term>
<listitem><para>Specifies the list of directories or files to
index (recursively for directories). The indexer will not
follow symbolic links inside the indexed trees by default
(see the <literal>followLinks</literal> options though).</para>
</listitem>
</varlistentry>
<varlistentry><term><literal>dbdir</literal></term>
<listitem><para>The name of the Xapian data directory. It
will be created if needed when the index is
initialized. If this is not an absolute path, it will be
interpreted relative to the configuration directory. The
value can have embedded spaces but starting or trailing
spaces will be trimmed. You cannot use quotes here.</para>
</listitem>
</varlistentry>
<varlistentry><term><literal>skippedNames</literal></term>
<listitem>
<para>A space-separated list of patterns for
names of files or directories that should be completely
ignored. The list defined in the default file is: </para>
<programlisting>
skippedNames = #* bin CVS Cache cache* caughtspam tmp .thumbnails .svn \
*~ recollrc
</programlisting>
<para>The list can be redefined for sub-directories, but is only
actually changed for the top level ones in
<literal>topdirs</literal>.</para>
<para>The top-level directories are not affected by this
list (that is, a directory in <literal>topdirs</literal>
might match and would still be indexed).</para>
<para>The list in the default configuration does not
exclude hidden directories (names beginning with a
dot), which means that it may index quite a few things
that you do not want. On the other hand, mail user
agents like <application>thunderbird</application>
usually store messages in hidden directories, and you
probably want this indexed. One possible solution is to
have <filename>.*</filename> in
<literal>skippedNames</literal>, and add things like
<filename>~/.thunderbird</filename> or
<filename>~/.evolution</filename> in
<literal>topdirs</literal>.</para>
</listitem>
</varlistentry>
<varlistentry><term><literal>skippedPaths</literal> and
<literal>daemSkippedPaths</literal> </term>
<listitem>
<para>A space-separated list of patterns for
<emphasis>paths</emphasis> of files or directories that should be skipped.
There is no default in the sample configuration file,
but the code always adds the configuration and database
directories in there.</para>
<para><literal>skippedPaths</literal> is used both by
batch and real time
indexing. <literal>daemSkippedPaths</literal> can be
used to specify things that should be indexed at
startup, but not monitored.</para>
<para>Example of use for skipping text files only in a
specific directory:</para>
<programlisting>
skippedPaths = ~/somedir/*.txt
</programlisting>
</listitem>
</varlistentry>
<varlistentry id="rcl.install.config.recollconf.followlinks">
<term><literal>followLinks</literal></term>
<listitem><para>Specifies if the indexer should follow
symbolic links while walking the file tree. The default is
to ignore symbolic links to avoid multiple indexing of
linked files. No effort is made to avoid duplication when
this option is set to true. This option can be set
individually for each of the <literal>topdirs</literal>
members by using sections. It can not be changed below the
<literal>topdirs</literal> level.</para>
</listitem>
</varlistentry>
<varlistentry><term><literal>loglevel,daemloglevel</literal></term>
<listitem><para>Verbosity level for recoll and
recollindex. A value of 4 lists quite a lot of
debug/information messages. 2 only lists errors. The
<literal>daem</literal>version is specific to the indexing monitor
daemon.</para>
</listitem>
</varlistentry>
<varlistentry><term><literal>logfilename,
daemlogfilename</literal></term>
<listitem><para>Where the messages should go. 'stderr' can
be used as a special value, and is the default. The
<literal>daem</literal>version is specific to the indexing monitor
daemon.</para>
</listitem>
</varlistentry>
<varlistentry><term><literal>indexstemminglanguages</literal></term>
<listitem><para>A list of languages for which the stem
expansion databases will be built. See recollindex(1) or
use the <literal>recollindex -l</literal> command for
possible values. You can add a stem expansion database for
a different language by using <command>recollindex
-s</command>, but it will be deleted during the next
indexing. Only languages listed in the configuration
file are permanent.</para>
</listitem>
</varlistentry>
<varlistentry><term><literal>defaultcharset</literal></term>
<listitem><para>The name of the character set used for
files that do not contain a character set definition (ie:
plain text files). This can be redefined for any
sub-directory. If it is not set at all, the character set
used is the one defined by the nls environment (LC_ALL,
LC_CTYPE, LANG), or iso8859-1 if nothing is set.</para>
<varlistentry><term><literal>maxfsoccuppc</literal></term>
<listitem><para>Maximum file system occupation before we
stop indexing. The value is a percentage, corresponding to
what the "Capacity" df output column shows. The default
value is 0, meaning no checking. </para>
</listitem>
</varlistentry>
<varlistentry><term><literal>idxflushmb</literal></term>
<listitem><para>Threshold (megabytes of new text data)
where we flush from memory to disk index. Setting this can
help control memory usage. A value of 0 means no explicit
flushing, letting Xapian use its own default, which is
flushing every 10000 documents (memory usage depends on
average document size). The default value is 10.</para>
</listitem>
</varlistentry>
<varlistentry><term><literal>filtersdir</literal></term>
<listitem><para>A directory to search for the external
filter scripts used to index some types of files. The
value should not be changed, except if you want to modify
one of the default scripts. The value can be redefined for
any sub-directory. </para>
</listitem>
</varlistentry>
<varlistentry><term><literal>iconsdir</literal></term>
<listitem><para>The name of the directory where
<command>recoll</command> result list icons are
stored. You can change this if you want different
images.</para>
</listitem>
</varlistentry>
<varlistentry><term><literal>guesscharset</literal></term>
<listitem><para>Decide if we try to guess the character
set of files if no internal value is available (ie: for
plain text files). This does not work well in general, and
should probably not be used. </para>
</listitem>
</varlistentry>
<varlistentry><term><literal>usesystemfilecommand</literal></term>
<listitem><para>Decide if we use the <command>file -i</command>
system command as a final step for determining the mime
type for a file (the main procedure uses suffix
associations as defined in the <filename>mimemap</filename>
file). This can be useful for files with suffix-less names,
but it will also cause the indexing of many bogus "text"
files.</para>
</listitem>
</varlistentry>
<varlistentry><term><literal>indexallfilenames</literal></term>
<listitem><para>&RCL; indexes file names in a special
section of the database to allow specific file names
searches using wild cards. This parameter decides if
file name indexing is performed only for files with mime
types that would qualify them for full text indexing, or
for all files inside the selected subtrees, independently of
mime type.</para>
</listitem>
</varlistentry>
<varlistentry><term><literal>idxabsmlen</literal></term>
<listitem><para>&RCL; stores an abstract for each indexed
file inside the database. This is so that they can be
displayed inside the result lists without decoding the
original file. This parameter defines the size of the
stored abstract (which can come from an actual section or
just be the beginning of the text). The default value is 250.
</para>
</listitem>
</varlistentry>
<varlistentry><term><literal>aspellLanguage</literal></term>
<listitem><para>Language definitions to use when creating
the aspell dictionary. The value must match a set of
aspell language definition files. You can type "aspell
config" to see where these are installed (look for
data-dir). The default if the variable is not set is to
use your desktop national language environment to guess
the value.</para>
</listitem>
</varlistentry>
<varlistentry><term><literal>noaspell</literal></term>
<listitem><para>If this is set, the aspell dictionary
generation is turned off. Useful for cases where you don't
need the functionality or when it is unusable because
aspell crashes during dictionary generation.</para>
</listitem>
</varlistentry>
</variablelist>
</sect2>
<sect2 id="rclinstall.config.mimemap">
<title>The mimemap file</title>
<para><filename>mimemap</filename> specifies the
file name extension to mime type mappings.</para>
<para>For file names without an extension, or with an unknown
one, the system's <command>file -i</command> command will be
executed to determine the mime type (this can be switched off
inside the main configuration file).</para>
<para>The mappings can be specified on a per-subtree basis,
which may be useful in some cases. Example:
<application>gaim</application> logs have a
<filename>.txt</filename> extension but
should be handled specially, which is possible because they
are usually all located in one place.</para>
<para><filename>mimemap</filename> also has a
<literal>recoll_noindex</literal> variable which is a list of
suffixes. Matching files will be skipped (which avoids
unnecessary decompressions or <command>file</command>
executions). This is partially redundant with
<literal>skippedNames</literal> in the main configuration
file, with two differences: it will not affect directories,
and it cannot be made dependant on the file-system location
(it is a configuration-wide parameter). You could accomplish
with <literal>skippedNames</literal> anything that
<literal>recoll_noindex</literal> does. The latter is used
mostly for things known to be unindexable by a given &RCL;
version. Having it there avoids cluttering the more
user-oriented and locally customized
<literal>skippedNames</literal>.</para>
</sect2>
<sect2 id="rclinstall.config.mimeconf">
<title>The mimeconf file</title>
<para><filename>mimeconf</filename> specifies how the
different mime types are handled for indexing, and which icons
are displayed in the <command>recoll</command> result lists.</para>
<para>Changing the parameters in the [index] section is
probably not a good idea except if you are a &RCL;
developer.</para>
<para>The [icons] section allows you to change the icons which
are displayed by <command>recoll</command> in the result
lists (the values are the basenames of the png images inside
the <filename>iconsdir</filename> directory (specified in
<filename>recoll.conf</filename>).</para>
</sect2>
<sect2 id="rclinstall.config.mimeview">
<title>The mimeview file</title>
<para><filename>mimeview</filename> specifies which programs
are started when you click on an <guilabel>Edit</guilabel>
link in a result list. Ie: HTML is normally displayed using
<application>firefox</application>, but you may prefer
<application>Konqueror</application>, your
<application>openoffice.org</application>
program might be named <command>oofice</command> instead of
<command>openoffice</command> etc.
</para>
<para>Changes to this file can be done by direct editing, or
through the <command>recoll</command> user preferences dialog.</para>
<para>As for the other configuration files, the normal usage
is to have a <filename>mimeview</filename> inside your own
configuration directory, with just the non-default entries,
which will override those from the central configuration
file.</para>
<para>Please note that these entries must be placed under a
<literal>[view]</literal> section.</para>
<para>If <guilabel>Use desktop preferences to choose
document editor</guilabel> is checked in the user preferences,
all <filename>mimeview</filename> entries will be ignored
except the one labelled <literal>application/x-all</literal>
(which is set to use <command>xdg-open</command> by default).</para>
</sect2>
<sect2 id="rclinstall.config.examples">
<title>Examples of configuration adjustments</title>
<sect3 id="rclinstall.config.examples.addview">
<title>Adding an external viewer for an non-indexed type</title>
<para>Imagine that you have some kind of file which does not
have indexable content, but for which you would like to have a
functional <guilabel>Edit</guilabel> link in the result list
(when found by file name). The file names end in
<replaceable>.blob</replaceable> and can be displayed by
application <replaceable>blobviewer</replaceable>.</para>
<para>You need two entries in the configuration files for this
to work:</para>
<itemizedlist>
<listitem><para>In <filename>$RECOLL_CONFDIR/mimemap</filename>
(typically <filename>~/.recoll/mimemap</filename>), add the
following line:</para>
<programlisting>
application/x-blobapp = .blob
</programlisting>
<para>Note that the mime type is made up here, and you could
call it <replaceable>diesel/oil</replaceable> just the
same.</para>
</listitem>
<listitem><para>In
<filename>$RECOLL_CONFDIR/mimeview</filename> under the
<literal>[view]</literal> section:</para>
<programlisting>
application/x-blobapp = blobviewer %f
</programlisting>
<para>We are supposing that
<replaceable>blobviewer</replaceable> wants a file name
parameter here, you would use <literal>%u</literal> if
it liked URLs better.</para>
</listitem>
</itemizedlist>
<para>If you just wanted to change the application used by
&RCL; to display a mime type which it already knows, you
would just need to edit <filename>mimeview</filename>. The
entries you add in your personal file override those in the
central configuration, which you do not need to alter</para>
</sect3>
<sect3 id="rclinstall.config.examples.addindex">
<title>Adding indexing support for a new file type</title>
<para>Let us now imagine that the above
<replaceable>.blob</replaceable> files actually contain
indexable text and that you know how to extract it with a
command line program. Getting &RCL; to index the files is
easy. You need to perform the above alteration, and also to
add data to the <filename>mimeconf</filename> file
(typically in <filename>~/.recoll/mimeconf</filename>):</para>
<itemizedlist>
<listitem><para>Under the <literal>[index]</literal>
section, add the following line (more about the
<replaceable>rclblob</replaceable> indexing script later):</para>
<programlisting>
application/x-blobapp = exec rclblob
</programlisting>
<para></para>
</listitem>
<listitem><para>Under the <literal>[icons]</literal>
section, you should choose an icon to be displayed for the
files inside the result lists. Icons are normally 64x64
pixels PNG files which live in
<filename>/usr/[local/]share/recoll/images</filename>.
</para>
</listitem>
<listitem><para>Under the <literal>[categories]</literal>
section, you should add the mime type where it makes sense
(you can also create a category). Categories may be used
for filtering in advanced search.</para>
</listitem>
</itemizedlist>
<para>The <replaceable>rclblob</replaceable> filter should
be an executable program or script which exists inside
<filename>/usr/[local/]share/recoll/filters</filename>. It
will be given a file name as argument and should output the
text contents in html format on the standard output.</para>
<para>You can find more details about writing a &RCL; filter
in the <link linkend="rcl.extending.filters">section about
writing filters</link></para>
</sect3>
</sect2>
</sect1>
<sect1 id="rcl.extending">
<title>Extending &RCL;</title>
<sect2 id="rcl.extending.filters">
<title>Writing a document filter</title>
<para>&RCL; filters are executable programs which
translate from a specific format (ie:
<application>openoffice</application>,
<application>acrobat</application>, etc.) to the &RCL;
indexing input format, which was chosen to be HTML.</para>
<para>&RCL; filters are usually shell-scripts, but this is in
no way necessary. These programs are extremely simple and most
of the difficulty lies in extracting the text from the native
format, not outputting what is expected by &RCL;. Happily
enough, most document formats already have translators or text
extractors which handle the difficult part and can be called
from the filter.</para>
<para>Filters are called with a single argument which is the
source file name. They should output the result to stdout.</para>
<para>The <literal>RECOLL_FILTER_FORPREVIEW</literal>
environment variable (values <literal>yes</literal>,
<literal>no</literal>) tells the filter if the operation is
for indexing or previewing. Some filters use this to output a
slightly different format. This is not essential.</para>
<para>The output HTML could be very minimal like the following
example:</para>
<programlisting><html><head>
<meta http-equiv="Content-Type" content="text/html;charset=UTF-8">
</head>
<body>some text content</body></html>
</programlisting>
<para>You should take care to escape some characters inside
the text by transforming them into appropriate
entities. "<literal>&</literal>" should be transformed into
"<literal>&amp;</literal>", "<literal><</literal>"
should be transformed into "<literal>&lt;</literal>".</para>
<para>The character set needs to be specified in the
header. It does not need to be UTF-8 (&RCL; will take care
of translating it), but it must be accurate for good
results.</para>
<para>&RCL; will also make use of other header fields if
they are present: <literal>title</literal>,
<literal>description</literal>,
<literal>keywords</literal>.</para>
<para>As of &RCL; release 1.9, filters also have the
possibility to "invent" field names. This should be output as
meta tags:</para>
<programlisting>
<meta name="somefield" content="Some textual data" />
</programlisting>
<para>In this case, a correspondance between field name and
&XAP; prefix should also be added to the
<filename>mimeconf</filename> file. See the existing entries
for inspiration. The field can then be used inside the query
language to narrow searches.</para>
<para>The easiest way to write a new filter is probably to start
from an existing one.</para>
</sect2>
</sect1>
</chapter>
</book>