Updated ICU config and adjusted description a little.

[pazpar2-moved-to-github.git] / doc / pazpar2_conf.xml

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<refentry id="pazpar2_conf">
 <refentryinfo>
  <productname>Pazpar2</productname>
  <productnumber>&version;</productnumber>
 </refentryinfo>
 <refmeta>
  <refentrytitle>Pazpar2 conf</refentrytitle>
  <manvolnum>5</manvolnum>
 </refmeta>
 
 <refnamediv>
  <refname>pazpar2_conf</refname>
  <refpurpose>Pazpar2 Configuration</refpurpose>
 </refnamediv>
 
 <refsynopsisdiv>
  <cmdsynopsis>
   <command>pazpar2.conf</command>
  </cmdsynopsis>
 </refsynopsisdiv>
 
 <refsect1><title>DESCRIPTION</title>
  <para>
   The Pazpar2 configuration file, together with any referenced XSLT files,
   govern Pazpar2's behavior as a client, and control the normalization and
   extraction of data elements from incoming result records, for the
   purposes of merging, sorting, facet analysis, and display.
  </para>
  
  <para>
   The file is specified using the option -f on the Pazpar2 command line.
   There is not presently a way to reload the configuration file without
   restarting Pazpar2, although this will most likely be added some time
   in the future.
  </para>
 </refsect1>
 
 <refsect1><title>FORMAT</title>
  <para>
   The configuration file is XML-structured. It must be valid XML. All
   elements specific to Pazpar2 should belong to the namespace
   <literal>http://www.indexdata.com/pazpar2/1.0</literal> 
   (this is assumed in the
   following examples). The root element is named <literal>pazpar2</literal>.
   Under the  root element are a number of elements which group categories of
   information. The categories are described below.
  </para>
  
  <refsect2 id="config-server"><title>server</title>
   <para>
    This section governs overall behavior of the client. The data
    elements are described below.
   </para>
   <variablelist> <!-- level 1 -->
    <varlistentry>
     <term>listen</term>
     <listitem>
      <para>
       Configures the webservice -- this controls how you can connect
       to Pazpar2 from your browser or server-side code. The
       attributes 'host' and 'port' control the binding of the
       server. The 'host' attribute can be used to bind the server to
       a secondary IP address of your system, enabling you to run
       Pazpar2 on port 80 alongside a conventional web server. You
       can override this setting on the command line using the option -h.
      </para>
     </listitem>
    </varlistentry>
    
    <varlistentry>
     <term>proxy</term>
     <listitem>
      <para>
       If this item is given, Pazpar2 will forward all incoming HTTP
       requests that do not contain the filename 'search.pz2' to the
       host and port specified using the 'host' and 'port'
       attributes. The 'myurl' attribute is required, and should provide
       the base URL of the server. Generally, the HTTP URL for the host
       specified in the 'listen' parameter. This functionality is
       crucial if you wish to use
       Pazpar2 in conjunction with browser-based code (JS, Flash,
       applets, etc.) which operates in a security sandbox. Such code
       can only connect to the same server from which the enclosing
       HTML page originated. Pazpar2s proxy functionality enables you
       to host all of the main pages (plus images, CSS, etc) of your
       application on a conventional webserver, while efficiently
       processing webservice requests for metasearch status, results,
       etc.
      </para>
     </listitem>
    </varlistentry>
    
    <varlistentry>
     <term>relevance</term>
     <listitem>
      <para>
       Specifies ICU tokenization and transformation rules
       for tokens that are used in Pazpar2's relevance ranking.  The 'id'
       attribute is currently not used, and the 'locale'
       attribute must be set to one of the locale strings
       defined in ICU. The child elements listed below can be
       in any order, except the 'index' element which logically
       belongs to the end of the list. The stated tokenization,
       transformation and charmapping instructions are performed
       in order from top to bottom. 
      </para>
      <variablelist> <!-- Level 2 -->
       <varlistentry><term>casemap</term>
        <listitem>
         <para>
          The attribute 'rule' defines the direction of the
          per-character casemapping, allowed values are "l"
          (lower), "u" (upper), "t" (title).  
         </para>
        </listitem>
       </varlistentry>
       <varlistentry><term>transform</term>
        <listitem>
         <para>
          Normalization and transformation of tokens follows
          the rules defined in the 'rule' attribute. For
          possible values we refer to the extensive ICU
          documentation found at the 
          <ulink url="&url.icu.transform;">ICU
           transformation</ulink> home page. Set filtering
          principles are explained at the 
          <ulink url="&url.icu.unicode.set;">ICU set and
           filtering</ulink> page.
         </para>
        </listitem>
       </varlistentry>
       <varlistentry><term>tokenize</term>
        <listitem>
         <para>
          Tokenization is the only rule in the ICU chain
          which splits one token into multiple tokens. The
          'rule' attribute may have the following values:
          "s" (sentence), "l" (line-break), "w" (word), and
          "c" (character), the later probably not being
          very useful in a pruning Pazpar2 installation. 
         </para>
        </listitem>
       </varlistentry>
      </variablelist>
     </listitem>
    </varlistentry>

    <varlistentry>
     <term>sort</term>
     <listitem>
      <para>
       Specifies ICU tokenization and transformation rules
       for tokens that are used in Pazpar2's sorting. The contents
       is similar to that of <literal>relevance</literal>.
      </para>
     </listitem>
    </varlistentry>
    
    <varlistentry>
     <term>mergekey</term>
     <listitem>
      <para>
       Specifies ICU tokenization and transformation rules
       for tokens that are used in Pazpar2's mergekey. The contents
       is similar to that of <literal>relevance</literal>.
      </para>
     </listitem>
    </varlistentry>
    
    <varlistentry>
     <term>service</term>
     <listitem>
      <para>
       This nested element controls the behavior of Pazpar2 with
       respect to your data model. In Pazpar2, incoming records are
       normalized, using XSLT, into an internal representation.
       The 'service' section controls the further processing and
       extraction of data from the internal representation, primarily
       through the 'metadata' sub-element.
      </para>
      
      <variablelist> <!-- Level 2 -->
       <varlistentry><term>metadata</term>
        <listitem>
         <para>
          One of these elements is required for every data element in
          the internal representation of the record (see
          <xref linkend="data_model"/>. It governs
          subsequent processing as pertains to sorting, relevance
          ranking, merging, and display of data elements. It supports
          the following attributes:
         </para>
         
         <variablelist> <!-- level 3 -->
          <varlistentry><term>name</term>
           <listitem>
            <para>
             This is the name of the data element. It is matched
             against the 'type' attribute of the
             'metadata' element 
             in the normalized record. A warning is produced if
             metadata elements with an unknown name are
             found in the 
             normalized record. This name is also used to
             represent 
             data elements in the records returned by the
             webservice API, and to name sort lists and browse
             facets.
            </para>
           </listitem>
          </varlistentry>
          
          <varlistentry><term>type</term>
           <listitem>
            <para>
             The type of data element. This value governs any
             normalization or special processing that might take
             place on an element. Possible values are 'generic'
             (basic string), 'year' (a range is computed if
             multiple years are found in the record). Note: This
             list is likely to increase in the future.
            </para>
           </listitem>
          </varlistentry>
          
          <varlistentry><term>brief</term>
           <listitem>
            <para>
             If this is set to 'yes', then the data element is
             includes in brief records in the webservice API. Note
             that this only makes sense for metadata elements that
             are merged (see below). The default value is 'no'.
            </para>
           </listitem>
          </varlistentry>
          
          <varlistentry><term>sortkey</term>
           <listitem>
            <para>
             Specifies that this data element is to be used for
             sorting. The possible values are 'numeric' (numeric
             value), 'skiparticle' (string; skip common, leading
             articles), and 'no' (no sorting). The default value is
             'no'.
            </para>
           </listitem>
          </varlistentry>
          
          <varlistentry><term>rank</term>
           <listitem>
            <para>
             Specifies that this element is to be used to
             help rank 
             records against the user's query (when ranking is
             requested). The value is an integer, used as a
             multiplier against the basic TF*IDF score. A value of
             1 is the base, higher values give additional
             weight to 
             elements of this type. The default is '0', which
             excludes this element from the rank calculation.
            </para>
           </listitem>
          </varlistentry>
          
          <varlistentry><term>termlist</term>
           <listitem>
            <para>
             Specifies that this element is to be used as a
             termlist, or browse facet. Values are tabulated from
             incoming records, and a highscore of values (with
             their associated frequency) is made available to the
             client through the webservice API. 
             The possible values
             are 'yes' and 'no' (default).
            </para>
           </listitem>
          </varlistentry>
          
          <varlistentry><term>merge</term>
           <listitem>
            <para>
             This governs whether, and how elements are extracted
             from individual records and merged into cluster
             records. The possible values are: 'unique' (include
             all unique elements), 'longest' (include only the
             longest element (strlen), 'range' (calculate a range
             of values across all matching records), 'all' (include
             all elements), or 'no' (don't merge; this is the
                          default);
            </para>
           </listitem>
          </varlistentry>

          <varlistentry><term>setting</term>
           <listitem>
            <para>
              This attribute allows you to make use of static database
              settings in the processing of records. Three possible values
              are allowed. 'no' is the default and doesn't do anything.
              'postproc' copies the value of a setting with the same name
              into the output of the normalization stylesheet(s). 'parameter'
              makes the value of a setting with the same name available 
              as a parameter to the normalization stylesheet, so you
              can further process the value inside of the stylesheet, or use
              the value to decide how to deal with other data values.
            </para>
            <para>
            </para>
              The purpose of using settings in this way can either be to
              control the behavior of normalization stylesheet in a database-
              dependent way, or to easily make database-dependent values
              available to display-logic in your user interface, without having
              to implement complicated interactions between the user interface
              and your configuration system.
           </listitem>
          </varlistentry>
         </variablelist> <!-- attributes to metadata -->
         
        </listitem>
       </varlistentry>
      </variablelist>     <!-- Data elements in service directive -->
     </listitem>
    </varlistentry>
   </variablelist>           <!-- Data elements in server directive -->
  </refsect2>
  
 </refsect1>
 
 <refsect1><title>EXAMPLE</title>
  <para>Below is a working example configuration:
  <screen><![CDATA[
<?xml version="1.0" encoding="UTF-8"?>
<pazpar2 xmlns="http://www.indexdata.com/pazpar2/1.0">

<server>
  <listen port="9004"/>
  <proxy host="us1.indexdata.com" myurl="us1.indexdata.com"/>

  <!-- optional ICU ranking configuration example -->
  <!--
  <icu_chain id="el:word" locale="el">
    <normalize rule="[:Control:] Any-Remove"/>
    <tokenize rule="l"/>
    <normalize rule="[[:WhiteSpace:][:Punctuation:]] Remove"/>
    <casemap rule="l"/>
    <index/>
  </icu_chain>
  -->

  <service>
    <metadata name="title" brief="yes" sortkey="skiparticle" merge="longest" rank="6"/>
    <metadata name="isbn" merge="unique"/>
    <metadata name="date" brief="yes" sortkey="numeric" type="year" merge="range"
            termlist="yes"/>
    <metadata name="author" brief="yes" termlist="yes" merge="longest" rank="2"/>
    <metadata name="subject" merge="unique" termlist="yes" rank="3"/>
    <metadata name="url" merge="unique"/>
  </service>
</server>

</pazpar2>
]]></screen>
  </para>
 </refsect1> 
 
 <refsect1 id="target_settings"><title>TARGET SETTINGS</title>
  <para>
   Pazpar2 features a cunning scheme by which you can associate various
   kinds of attributes, or settings with search targets. This can be done
   through XML files which are read at startup; each file can associate
   one or more settings with one or more targets. The file format is generic
   in nature, designed to support a wide range of application requirements. The
   settings can be purely technical things, like, how to perform a title
   search against a given target, or it can associate arbitrary name=value
   pairs with groups of targets -- for instance, if you would like to
   place all commercial full-text bases in one group for selection
   purposes, or you would like to control what targets are accessible
   to users by default. Per-database settings values can even be used
   to drive sorting, facet/termlist generation, or end-user interface display
   logic.
  </para>
  
  <para>
   During startup, Pazpar2 will recursively read a specified directory
   (can be identified in the pazpar2.cfg file or on the command line), and
   process any settings files found therein.
  </para>
  
  <para>
   Clients of the Pazpar2 webservice interface can selectively override
   settings for individual targets within the scope of one session. This
   can be used in conjunction with an external authentication system to
   determine which resources are to be accessible to which users. Pazpar2
   itself has no notion of end-users, and so can be used in conjunction
   with any type of authentication system. Similarly, the authentication
   tokens submitted to access-controlled search targets can similarly be
   overridden, to allow use of Pazpar2 in a consortial or multi-library
   environment, where different end-users may need to be represented to
   some search targets in different ways. This, again, can be managed
   using an external database or other lookup mechanism. Setting overrides
   can be performed either using the 'init' or the 'settings' webservice
   command.
  </para>
  
  <para>
   In fact, every setting that applies to a database (except pz:id, which
   can only be used for filtering targets to use for a search) can be overridden
   on a per-session basis. This allows the client to override specific CCL fields
   for searching, etc., to meet the needs of a session or user.
  </para>
  
  <para>
   Finally, as an extreme case of this, the webservice client can
   introduce entirely new targets, on the fly, as part of the init or
   settings command. This is useful if you desire to manage information
   about your search targets in a separate application such as a database.
   You do not need any static settings file whatsoever to run Pazpar2 -- as
   long as the webservice client is prepared to supply the necessary
   information at the beginning of every session.
  </para>
  
  <note>
   <para>
    The following discussion of practical issues related to session and settings
    management are cast in terms of a user interface based on Ajax/Javascript
    technology. It would apply equally well to many other kinds of browser-based logic.
   </para>
  </note>
  
  <para>
   Typically, a Javascript client is not allowed to  directly alter the parameters
   of a session. There are two reasons for this. One has to do with access
   to information; typically, information about a user will be stored in a
   system on the server side, or it will be accessible in some way from the server.
   However, since the Javascript client cannot be entirely trusted (some hostile
   agent might in fact 'pretend' to be a regular ws client), it is more robust
   to control session settings from scripting that you run as part of your
   webserver. Typically, this can be handled during the session initialization,
   as follows:
  </para>
  
  <para>
   Step 1: The Javascript client loads, and asks the webserver for a new Pazpar2
   session ID. This can be done using a Javascript call, for instance. Note that
   it is possible to submit Ajax HTTPXmlRequest calls either to Pazpar2 or to the
   webserver that Pazpar2 is proxying for. See (XXX Insert link to Pazpar2 protocol).
    </para>
  
  <para>
   Step 2: Code on the webserver authenticates the user, by database lookup,
   LDAP access, NCIP, etc. Determines which resources the user has access to,
   and any user-specific parameters that are to be applied during this session.
  </para>
  
  <para>
   Step 3: The webserver initializes a new Pazpar2 settings, and sets user-specific
   parameters as necessary, using the init webservice command. A new session ID is
   returned.
  </para>
  
  <para>
   Step 4: The webserver returns this session ID to the Javascript client, which then
   uses the session ID to submit searches, show results, etc.
  </para>
  
  <para>
   Step 5: When the Javascript client ceases to use the session, Pazpar2 destroys
   any session-specific information.
  </para>

  <refsect2><title>SETTINGS FILE FORMAT</title>
   <para>
    Each file contains a root element named &lt;settings&gt;. It may
    contain one or more &lt;set&gt; elements. The settings and set
    elements may contain the following attributes. Attributes in the set node
    overrides those in the setting root element. Each set node must
    specify (directly, or inherited from the parent node) at least a
    target, name, and value.
   </para>
   
   <variablelist> 
    <varlistentry>
     <term>target</term>
     <listitem>
      <para>
       This specifies the search target to which this setting should be
       applied. Targets are identified by their Z39.50 URL, generally
       including the host, port, and database name, (e.g.
       <literal>bagel.indexdata.com:210/marc</literal>).
       Two wildcard forms are accepted:
       * (asterisk) matches all known targets;
       <literal>bagel.indexdata.com:210/*</literal> matches all
       known databases on the given host.
      </para>
      <para>
       A precedence system determines what happens if there are
       overlapping values for the same setting name for the same
       target. A setting for a specific target name overrides a
       setting which specifies target using a wildcard. This makes it
       easy to set defaults for all targets, and then override them
       for specific targets or hosts. If there are
       multiple overlapping settings with the same name and target
       value, the 'precedence' attribute determines what happens.
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term>name</term>
     <listitem>
      <para>
       The name of the setting. This can be anything you like.
       However, Pazpar2 reserves a number of setting names for
       specific purposes, all starting with 'pz:', and it is a good
       idea to avoid that prefix if you make up your own setting
       names. See below for a list of reserved variables.
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term>value</term>
     <listitem>
      <para>
       The value of the setting. Generally, this can be anything you
       want -- however, some of the reserved settings may expect
       specific kinds of values.
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term>precedence</term>
     <listitem>
      <para>
       This should be an integer. If not provided, the default value
       is 0. If two (or more) settings have the same content for
       target and name, the precedence value determines the outcome.
       If both settings have the same precedence value, they are both
       applied to the target(s). If one has a higher value, then the
       value of that setting is applied, and the other one is ignored.
      </para>
     </listitem>
    </varlistentry>
   </variablelist>
   
   <para>
    By setting defaults for target, name, or value in the root
    settings node, you can use the settings files in many different
    ways. For instance, you can use a single file to set defaults for
    many different settings, like search fields, retrieval syntaxes,
    etc. You can have one file per server, which groups settings for
    that server or target. You could also have one file which associates
    a number of targets with a given setting, for instance, to associate
    many databases with a given category or class that makes sense
    within your application.
   </para>
   
   <para>
    The following examples illustrate uses of the settings system to
    associate settings with targets to meet different requirements.
   </para>
   
   <para>
    The example below associates a set of default values that can be
    used across many targets. Note the wildcard for targets.
    This associates the given settings with all targets for which no
    other information is provided.
    <screen><![CDATA[
<settings target="*">

  <!-- This file introduces default settings for pazpar2 -->

  <!-- mapping for unqualified search -->
  <set name="pz:cclmap:term" value="u=1016 t=l,r s=al"/>

  <!-- field-specific mappings -->
  <set name="pz:cclmap:ti" value="u=4 s=al"/>
  <set name="pz:cclmap:su" value="u=21 s=al"/>
  <set name="pz:cclmap:isbn" value="u=7"/>
  <set name="pz:cclmap:issn" value="u=8"/>
  <set name="pz:cclmap:date" value="u=30 r=r"/>

  <!-- Retrieval settings -->

  <set name="pz:requestsyntax" value="marc21"/>
  <set name="pz:elements" value="F"/>

  <!-- Query encoding -->
  <set name="pz:queryencoding" value="iso-8859-1"/>

  <!-- Result normalization settings -->

  <set name="pz:nativesyntax" value="iso2709"/>
  <set name="pz:xslt" value="../etc/marc21.xsl"/>

</settings>

        ]]></screen>
   </para>
   
   <para>
    The next example shows certain settings overridden for one target,
    one which returns XML records containing DublinCore elements, and
    which furthermore requires a username/password.
    <screen><![CDATA[
<settings target="funkytarget.com:210/db1">
  <set name="pz:requestsyntax" value="xml"/>
  <set name="pz:nativesyntax" value="xml"/>
  <set name="pz:xslt" value="../etc/dublincore.xsl"/>

  <set name="pz:authentication" value="myuser/password"/>
</settings>
        ]]></screen>
   </para>
   
   <para>
    The following example associates a specific name/value combination
    with a number of targets. The targets below are access-restricted,
    and can only be used by users with special credentials.
    <screen><![CDATA[
<settings name="pz:allow" value="0">
  <set target="funkytarget.com:210/*"/>
  <set target="commercial.com:2100/expensiveDb"/>
</settings>
        ]]></screen>
   </para>
   
  </refsect2>
  
  <refsect2><title>RESERVED SETTING NAMES</title>
   <para>
    The following setting names are reserved by Pazpar2 to control the
    behavior of the client function.
   </para>
   
   <variablelist>
    <varlistentry>
     <term>pz:cclmap:xxx</term>
     <listitem>
      <para>
       This establishes a CCL field definition or other setting, for
       the purpose of mapping end-user queries. XXX is the field or
       setting name, and the value of the setting provides parameters
       (e.g. parameters to send to the server, etc.). Please consult
       the YAZ manual for a full overview of the many capabilities of
       the powerful and flexible CCL parser.
      </para>
      <para>
       Note that it is easy to establish a set of default parameters,
       and then override them individually for a given target.
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term>pz:requestsyntax</term>
     <listitem>
      <para>
       This specifies the record syntax to use when requesting
       records from a given server. The value can be a symbolic name like
       marc21 or xml, or it can be a Z39.50-style dot-separated OID.
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term>pz:elements</term>
     <listitem>
      <para>
       The element set name to be used when retrieving records from a
       server.
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term>pz:piggyback</term>
     <listitem>
      <para>
       Piggybacking enables the server to retrieve records from the
       server as part of the search response in Z39.50. Almost all
       servers support this (or fail it gracefully), but a few
       servers will produce undesirable results.
       Set to '1' to enable piggybacking, '0' to disable it. Default
       is 1 (piggybacking enabled).
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term>pz:nativesyntax</term>
     <listitem>
      <para>
       The representation (syntax) of the retrieval records. Currently
       recognized values are iso2709 and xml.
      </para>
      <para>
       For iso2709, can also specify a native character set, e.g. "iso2709;latin-1".
       If no character set is provided, MARC-8 is assumed.
      </para>
      <para>
        If pz:nativesyntax is not specified, pazpar2 will attempt to determine
        the value based on the response from the server.
      </para>
     </listitem>
    </varlistentry>

    <varlistentry>
     <term>pz:queryencoding</term>
     <listitem>
      <para>
        The encoding of the search terms that a target accepts. Most
        targets do not honor UTF-8 in which case this needs to be specified.
        Each term in a query will be converted if this setting is given.
      </para>
     </listitem>
    </varlistentry>

    <varlistentry>
     <term>pz:xslt</term>
     <listitem>
      <para>
       Provides the path of an XSLT stylesheet which will be used to
       map incoming records to the internal representation.
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term>pz:authentication</term>
     <listitem>
      <para>
       Sets an authentication string for a given server. See the section on
       authorization and authentication for discussion.
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term>pz:allow</term>
     <listitem>
      <para>
       Allows or denies access to the resources it is applied to. Possible
       values are '0' and '1'. The default is '1' (allow access to this resource).
       See the manual section on authorization and authentication for discussion
       about how to use this setting.
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term>pz:maxrecs</term>
     <listitem>
      <para>
       Controls the maximum number of records to be retrieved from a
       server. The default is 100.
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term>pz:id</term>
     <listitem>
      <para>
       This setting can't be 'set' -- it contains the ID (normally
       ZURL) for a given target, and is useful for filtering --
       specifically when you want to select one or more specific
       targets in the search command.
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term>pz:zproxy</term>
     <listitem>
      <para>
       The 'pz:zproxy' setting has the value syntax 
       'host.internet.adress:port', it is used to tunnel Z39.50
       requests through the named Z39.50 proxy.
      </para>
     </listitem>
    </varlistentry>

    <varlistentry>
     <term>pz:apdulog</term>
     <listitem>
      <para>
       If the 'pz:apdulog' setting is defined and has other value than 0,
       then Z39.50 APDUs are written to the log.
      </para>
     </listitem>
    </varlistentry>

    <varlistentry>
      <term>pz:sru</term>
      <listitem>
        <para>
          This setting enables SRU/SRW support. It has three possible settings.
          'get', enables SRU access through GET requests. 'post' enables SRU/POST
          support, less commonly supported, but useful if very large requests are
          to be submitted. 'srw' enables the SRW variation of the protocol.
        </para>
      </listitem>
    </varlistentry>

    <varlistentry>
      <term>pz:sru_version</term>
      <listitem>
        <para>
          This allows SRU version to be specified. If unset Pazpar2
          will the default of YAZ (currently 1.2). Should be set
          to 1.1 or 1.2.
        </para>
      </listitem>
    </varlistentry>

    <varlistentry>
      <term>pz:pqf_prefix</term>
      <listitem>
        <para>
          Allows you to specify an arbitrary PQF query language substring. The provided
          string is prefixed the user's query after it has been normalized to PQF
          internally in pazpar2. This allows you to attach complex 'filters' to
          queries for a gien target, sometimes necessary to select sub-catalogs
          in union catalog systems, etc.
        </para>
      </listitem>
    </varlistentry>
   </variablelist>
  </refsect2>

 </refsect1>
 <refsect1><title>SEE ALSO</title>
  <para>
   <citerefentry>
    <refentrytitle>pazpar2</refentrytitle>
    <manvolnum>8</manvolnum>
   </citerefentry>
   <citerefentry>
    <refentrytitle>yaz-icu</refentrytitle>
    <manvolnum>1</manvolnum>
   </citerefentry>
   <citerefentry>
    <refentrytitle>pazpar2_protocol</refentrytitle>
    <manvolnum>7</manvolnum>
   </citerefentry>
  </para>
 </refsect1>
</refentry>
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