Separate chapter about ranking

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

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<refentry id="pazpar2_conf">
 <refentryinfo>
  <productname>Pazpar2</productname>
  <productnumber>&version;</productnumber>
  <info><orgname>Index Data</orgname></info>
 </refentryinfo>
 
 <refmeta>
  <refentrytitle>Pazpar2 conf</refentrytitle>
  <manvolnum>5</manvolnum>
  <refmiscinfo class="manual">File formats and conventions</refmiscinfo>
 </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 well-formed 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-threads">
   <title>threads</title>
   <para>
    This section is optional and is supported for Pazpar2 version 1.3.1 and
    later . It is identified by element "<literal>threads</literal>" which
    may include one attribute "<literal>number</literal>" which specifies
    the number of worker-threads that the Pazpar2 instance is to use.
    A value of 0 (zero) disables worker-threads (all work is carried out
    in main thread).
   </para>
  </refsect2>
  <refsect2 id="config-server">
   <title>server</title>
   <para>
    This section governs overall behavior of a server endpoint. It is identified
    by the element "server" which takes an optional attribute, "id", which
    identifies this particular Pazpar2 server. Any string value for "id"
    may be given.
   </para>
   <para>
    The data
    elements are described below. From Pazpar2 version 1.2 this is
    a repeatable element.
   </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>icu_chain</term>
     <listitem>
      <para>
       Specifies character set normalization for relevancy / sorting /
       mergekey and facets - for the server. These definitions serves as
       default for services that don't have these given. For the meaning
       of these settings refer to the
       <xref linkend="icuchain"/> element inside service.
      </para>
     </listitem>
    </varlistentry>
    
    <varlistentry>
     <term>relevance / sort / mergekey / facet</term>
     <listitem>
      <para>
       Obsolete. Use element icu_chain instead.
      </para>
     </listitem>
    </varlistentry>
    
    <varlistentry>
     <term>settings</term>
     <listitem>
      <para>
       Specifies target settings for the server.. These settings serves
       as default for all services which don't have these given.
       The settings element requires one attribute 'src' which specifies
       a settings file or a directory . If a directory is given all
       files with suffix <filename>.xml</filename> is read from this
       directory. Refer to 
       <xref linkend="target_settings"/> for more information.
      </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>
      <para>
       Pazpar2 version 1.2 and later allows multiple service elements.
       Multiple services must be given a unique ID by specifying
       attribute <literal>id</literal>.
       A single service may be unnamed (service ID omitted). The
       service ID is referred to in the
       <link linkend="command-init"><literal>init</literal></link> webservice
       command's <literal>service</literal> parameter.
      </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 valus is of the form 
             <literallayout>
              M [F N]
             </literallayout>
             where M is an integer, used as a
             weight 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>
            <para>
             F is a CCL field and N is the multipler for terms
             that matches those part of the CCL field in search.
             The F+N combo allows the system to use a different
             multipler for a certain field. For example, a rank value of
             "<literal>1 au 3</literal>" gives a multipler of 3 for
             all terms part of the au(thor) terms and 1 for everything else.
            </para>
            <para>
             For Pazpar2 1.6.13 and later, the rank may also defined
             "per-document", by the normalization stylesheet. 
            </para>
            <para>
             The per field rank was introduced in Pazpar2 1.6.15. Earlier
             releases only allowed a rank value M (simple integer).
            </para>
            See <xref linkend="relevance_ranking"/> for more
            about ranking.
           </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>mergekey</term>
           <listitem>
            <para>
             If set to '<literal>required</literal>', the value of this
             metadata element is appended to the resulting mergekey if
             the metadata is present in a record instance.
             If the metadata element is not present, the a unique mergekey
             will be generated instead.
            </para>
            <para>
             If set to '<literal>optional</literal>', the value of this
             metadata element is appended to the resulting mergekey if the
             the metadata is present in a record instance. If the metadata
             is not present, it will be empty.
            </para>
            <para>
             If set to '<literal>no</literal>' or the mergekey attribute is
             omitted, the metadata will not be used in the creation of a
             mergekey.
            </para>
           </listitem>
          </varlistentry>

          <varlistentry>
           <term id="facetrule">facetrule</term>
           <listitem>
            <para>
             Specifies the ICU rule set to be used for normalizing
             facets. If facetrule is omitted from metadata, the
             rule set 'facet' is used.
            </para>
           </listitem>
          </varlistentry>
          
          <varlistentry>
           <term id="metadata_limitmap">limitmap</term>
           <listitem>
            <para>
             Specifies a default limitmap for this field. This is to avoid mass 
             configuring of targets. However it is important to review/do this on a per
             target since it is usually target-specific. See limitmap for format. 
            </para>
           </listitem>
          </varlistentry>
          
          <varlistentry>
           <term id="metadata_facetmap">facetmap</term>
           <listitem>
            <para>
             Specifies a default facetmap for this field. This is to avoid mass 
             configuring of targets. However it is important to review/do this on a per
             target since it is usually target-specific. See facetmap for format. 
            </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>
             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.
            </para>
           </listitem>
          </varlistentry>
          
         </variablelist> <!-- attributes to metadata -->
         
        </listitem>
       </varlistentry>

       <varlistentry>
        <term id="servicexslt" xreflabel="xslt">xslt</term>
        <listitem>
         <para>
          Defines a XSLT stylesheet. The <literal>xslt</literal>
          element takes exactly one attribute <literal>id</literal>
          which names the stylesheet. This can be referred to in target
          settings <xref linkend="pzxslt"/>.
         </para>
         <para>
          The content of the xslt element is the embedded stylesheet XML
         </para>
        </listitem>
       </varlistentry>
       <varlistentry>
        <term id="icuchain" xreflabel="icu_chain">icu_chain</term>
        <listitem>
         <para>
          Specifies a named ICU rule set. The icu_chain element must include
          attribute 'id' which specifies the identifier (name) for the ICU
          rule set.
          Pazpar2 uses the particular rule sets for particular purposes.
          Rule set 'relevance' is used to normalize
          terms for relevance ranking. Rule set 'sort' is used to 
          normalize terms for sorting. Rule set 'mergekey' is used to
          normalize terms for making a mergekey and, finally. Rule set 'facet'
          is normally used to normalize facet terms, unless
          <xref linkend="facetrule">facetrule</xref> is given for a
          metadata field.
         </para>
         <para>
          The icu_chain element must also include a 'locale'
          attribute which 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>
         <para>
          From Pazpar2 version 1.1 the ICU wrapper from YAZ is used.
          Refer to the <ulink url="&url.yaz.yaz-icu;">yaz-icu</ulink>
          utility for more information.
         </para>
        </listitem>
       </varlistentry>
       
       <varlistentry>
        <term>relevance</term>
        <listitem>
         <para>
          Specifies the ICU rule set used for relevance ranking.
          The child element of 'relevance' must be 'icu_chain' and the
          'id' attribute of the icu_chain is ignored. This
          definition is obsolete and should be replaced by the equivalent
          construct:
          <screen>
           &lt;icu_chain id="relevance" locale="en">..&lt;icu_chain>
          </screen>
         </para>
        </listitem>
       </varlistentry>
       
       <varlistentry>
        <term>sort</term>
        <listitem>
         <para>
          Specifies the ICU rule set used for sorting.
          The child element of 'sort' must be 'icu_chain' and the
          'id' attribute of the icu_chain is ignored. This
          definition is obsolete and should be replaced by the equivalent
          construct:
          <screen>
           &lt;icu_chain id="sort" locale="en">..&lt;icu_chain>
          </screen>
         </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 child element of 'mergekey' must be 'icu_chain' and the
          'id' attribute of the icu_chain is ignored. This
          definition is obsolete and should be replaced by the equivalent
          construct:
          <screen>
           &lt;icu_chain id="mergekey" locale="en">..&lt;icu_chain>
          </screen>
         </para>
        </listitem>
       </varlistentry>

       <varlistentry>
        <term>facet</term>
        <listitem>
         <para>
          Specifies ICU tokenization and transformation rules
          for tokens that are used in Pazpar2's facets.
          The child element of 'facet' must be 'icu_chain' and the
          'id' attribute of the icu_chain is ignored. This
          definition is obsolete and should be replaced by the equivalent
          construct:
          <screen>
           &lt;icu_chain id="facet" locale="en">..&lt;icu_chain>
          </screen>
         </para>
        </listitem>
       </varlistentry>

       <varlistentry>
        <term>ccldirective</term>
        <listitem>
         <para>
          Customizes the CCL parsing (interpretation of query parameter
          in search).
          The name and value of the CCL directive is gigen by attributes
          'name' and 'value' respectively. Refer to possible list of names
          in the
          <ulink 
              url="http://www.indexdata.com/yaz/doc/tools.html#ccl.directives.table">
           YAZ manual
           </ulink>.
         </para>
        </listitem>
       </varlistentry>

       <varlistentry>
        <term>rank</term>
        <listitem>
         <para>
          Customizes the ranking (relevance) algorithm. Also known as
          rank tweaks. The rank element
          accepts the following attributes - all being optional:
         </para>
         <variablelist>
          <varlistentry>
           <term>cluster</term>
           <listitem>
            <para>
             Attribute 'cluster' is a boolean
             that controls whether Pazpar2 should boost ranking for merged
             records. Is 'yes' by default. A value of 'no' will make
             Pazpar2 average ranking of each record in a cluster.
            </para>
           </listitem>
          </varlistentry>
          <varlistentry>
           <term>debug</term>
           <listitem>
            <para>
             Attribute 'debug' is a boolean
             that controls whether Pazpar2 should include details
             about ranking for each document in the show command's
             response. Enable by using value "yes", disable by using
             value "no" (default).
            </para>
           </listitem>
          </varlistentry>
          <varlistentry>
           <term>follow</term>
           <listitem>
            <para>
             Attribute 'follow' is a a floating point number greater than
             or equal to 0. A positive number will boost weight for terms
             that occur close to each other (proximity, distance).
             A value of 1, will double the weight if two terms are in
             proximity distance of 1 (next to each other). The default
             value of 'follow' is 0 (order will not affect weight).
            </para>
           </listitem>
          </varlistentry>
          <varlistentry>
           <term>lead</term>
           <listitem>
            <para>
             Attribute 'lead' is a floating point number.
             It controls if term weight should be reduced by position
             from start in a metadata field. A positive value of 'lead'
             will reduce weight as it apperas further away from the lead
             of the field. Default value is 0 (no reduction of weight by
             position).
            </para>
           </listitem>
          </varlistentry>
          <varlistentry>
           <term>length</term>
           <listitem>
            <para>
             Attribute 'length' determines how/if term weight should be
             divided by lenght of metadata field. A value of "linear"
             divide by length. A value of "log" will divide by log2(length).
             A value of "none" will leave term weight as is (no division).
             Default value is "linear".
            </para>
           </listitem>
          </varlistentry>
         </variablelist>
         <para>
          Refer to <xref linkend="relevance_ranking"/> to see how
          these tweaks are used in computation of score.
         </para>
         <para>
          Customization of ranking algorithm was introduced with
          Pazpar2 1.6.18. The semantics of some of the fields changed
          in versions up to 1.6.21.
         </para>
        </listitem>
       </varlistentry>
       
       <varlistentry id="sort-default">
        <term>sort-default</term>
        <listitem>
         <para>
          Specifies the default sort criteria (default 'relevance'),
          which previous was hard-coded as default criteria in search. 
          This is a fix/work-around to avoid re-searching when using 
          target-based sorting. In order for this to work efficient, 
          the search must also have the sort critera parameter; otherwise 
          pazpar2 will do re-searching on search criteria changes, if
          changed between search and show command.
         </para>
         <para>
          This configuration was added in pazpar2 1.6.20.
         </para>
        </listitem>
       </varlistentry>

<!--       
       <varlistentry>
        <term>set</term>
        <listitem>
         <para>
          Specifies a variable that will be inherited by all targets defined in settings
          <screen>
           &lt;set name="test" value="en"..&lt;set>
          </screen>
         </para>
        </listitem>
       </varlistentry>
-->   
       <varlistentry>
        <term>settings</term>
        <listitem>
         <para>
          Specifies target settings for this service. Refer to
          <xref linkend="target_settings"/>.
         </para>
        </listitem>
       </varlistentry>

       <varlistentry>
        <term>timeout</term>
        <listitem>
         <para>
          Specifies timeout parameters for this service.
          The <literal>timeout</literal>
          element supports the following attributes: 
          <literal>session</literal>, <literal>z3950_operation</literal>,
          <literal>z3950_session</literal> which specifies
          'session timeout', 'Z39.50 operation timeout',
          'Z39.50 session timeout' respectively. The Z39.50 operation
          timeout is the time Pazpar2 will wait for an active Z39.50/SRU
          operation before it gives up (times out). The Z39.50 session
          time out is the time Pazpar2 will keep the session alive for
          an idle session (no operation).
         </para>
         <para>
          The following is recommended but not required:
          z3950_operation (30) &lt; session (60) &lt; z3950_session (180) .
          The default values are given in parantheses.
         </para>
        </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:
  </para>
  <screen>
   <![CDATA[
<?xml version="1.0" encoding="UTF-8"?>
<pazpar2 xmlns="http://www.indexdata.com/pazpar2/1.0">

 <threads number="10"/>
 <server>
  <listen port="9004"/>
  <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" limitmap="local:"/>
   <metadata name="url" merge="unique"/>
   <icu_chain id="relevance" locale="el">
    <transform rule="[:Control:] Any-Remove"/>
    <tokenize rule="l"/>
    <transform rule="[[:WhiteSpace:][:Punctuation:]] Remove"/>
    <casemap rule="l"/>
   </icu_chain>
   <settings src="mysettings"/>
   <timeout session="60"/>
  <service>
 </server>
</pazpar2>
   ]]>
  </screen>
 </refsect1> 

 <refsect1 id="config-include">
  <title>INCLUDE FACILITY</title>
  <para>
   The XML configuration may be partitioned into multiple files by using
   the <literal>include</literal> element which takes a single attribute,
   <literal>src</literal>. The of the <literal>src</literal> attribute is
   regular Shell like glob-pattern. For example,
   <screen><![CDATA[
   <include src="/etc/pazpar2/conf.d/*.xml"/>
   ]]></screen>
  </para>
  <para>
   The include facility requires Pazpar2 version 1.2.
  </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
   <link linkend="command-init">init</link> or the 
   <link linkend="command-settings">settings</link> 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
   <link linkend="command-init">init</link> or
   <link linkend="command-settings">settings</link> 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>
      <para>
       For Pazpar2 1.6.4 or later, the target ID may be user-defined, in
       which case, the actual host, port, etc is given by setting
       <xref linkend="pzurl"/>.
      </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"/>
    
    <set name="pz:limitmap:title" value="rpn:@attr 1=4 @attr 6=3"/>
    <set name="pz:limitmap:date" value="ccl:date"/>

    <!-- 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 id="requestsyntax">
     <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>
       Specifies how Pazpar2 shoule map retrieved records to XML. Currently
       supported values are <literal>xml</literal>,
       <literal>iso2709</literal> and <literal>txml</literal>.
      </para>
      <para>
       The value <literal>iso2709</literal> makes Pazpar2 convert retrieved
       MARC records to MARCXML. In order to convert to XML, the exact
       chacater set of the MARC must be known (if not, the resulting
       XML is probably not well-formed). The character set may be 
       specified by adding:
       <literal>;charset=</literal><replaceable>charset</replaceable> to
       <literal>iso2709</literal>. If omitted, a charset of
       MARC-8 is assumed. This is correct for most MARC21/USMARC records.
      </para>
      <para>
       The value <literal>txml</literal> is like <literal>iso2709</literal>
       except that records are converted to TurboMARC instead of MARCXML.
      </para>
      <para>
       The value <literal>xml</literal> is used if Pazpar2 retrieves
       records that are already XML (no conversion takes place).
      </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:negotiation_charset</term>
     <listitem>
      <para>
       Sets character set for Z39.50 negotiation. Most targets do not support
       this, and some will even close connection if set (crash on server
       side or similar). If set, you probably want to set it to
       <literal>UTF-8</literal>.
      </para>
     </listitem>
    </varlistentry>

    <varlistentry>
     <term id="pzxslt" xreflabel="pz:xslt">pz:xslt</term>
     <listitem>
      <para>
       Is a comma separated list of of stylesheet names that specifies
       how to convert incoming records to the internal representation.
      </para>
      <para>
       For each name, the embedded stylesheets (XSL) that comes with the
       service definition are consulted first and takes precedence over
       external files; see <xref linkend="servicexslt"/>
       of service definition).
       If the name does not match an embedded stylesheet it is
       considered a filename.
      </para>
      <para>
       The suffix of each file specifies the kind of tranformation.
       Suffix "<literal>.xsl</literal>" makes an XSL transform. Suffix
       "<literal>.mmap</literal>" will use the MMAP transform (described below).
      </para>
      <para>
       The special value "<literal>auto</literal>" will use a file
       which is the <link linkend="requestsyntax">pz:requestsyntax's</link>
       value followed by
       <literal>'.xsl'</literal>.
      </para>
      <para>
       When mapping MARC records, XSLT can be bypassed for increased 
       performance with the alternate "MARC map" format.  Provide the
       path of a file with extension ".mmap" containing on each line:
       <programlisting>
       &lt;field&gt; &lt;subfield&gt; &lt;metadata element&gt;</programlisting>
       For example:
       <programlisting>
        245 a title
        500 $ description
        773 * citation
       </programlisting>
       To map the field value specify a subfield of '$'.  To store a 
       concatenation of all subfields, specify a subfield of '*'.
      </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:presentchunk</term>
     <listitem>
      <para>
       Controls the chunk size in present requests. Pazpar2 will 
       make (maxrecs / chunk) request(s). The default is 20.
      </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
       <ulink url="&url.sru;">SRU</ulink>/<ulink url="&url.solr;">Solr</ulink>
       support.
       It has four 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 (SRU over SOAP) variation of
       the protocol.
      </para>
      <para>
       A value of 'solr' enables Solr client support. This is supported
       for Pazpar version 1.5.0 and later.
      </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. For Solr, the current supported/tested version is 1.4 and 3.x.
      </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 to 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 given
       target, sometimes necessary to select sub-catalogs
       in union catalog systems, etc.
      </para>
     </listitem>
    </varlistentry>
    
    <varlistentry>
     <term>pz:pqf_strftime</term>
     <listitem>
      <para>
       Allows you to extend a query with dates and operators.
       The provided string allows certain substitutions and serves as a
       format string.
       The special two character sequence '%%' gets converted to the
       original query. Other characters leading with the percent sign are
       conversions supported by strftime.
       All other characters are copied verbatim. For example, the string
       <literal>@and @attr 1=30 @attr 2=3 %Y %%</literal>
       would search for current year combined with the original PQF (%%).
      </para>
      <para>
       This setting can also be used as more general alternative to
       pz:pqf_prefix -- a way of embedding the submitted query
       anywhere in the string rather than appending it to prefix.  For
       example, if it is desired to omit all records satisfying the
       query <literal>@attr 1=pica.bib 0007</literal> then this
       subquery can be combined with the submitted query as the second
       argument of <literal>@andnot</literal> by using the
       pz:pqf_strftime value <literal>@not %% @attr 1=pica.bib
       0007</literal>.
      </para>
     </listitem>
    </varlistentry>
    
    <varlistentry>
     <term>pz:sort</term>
     <listitem>
      <para>
       Specifies sort criteria to be applied to the result set.
       Only works for targets which support the sort service.
      </para>
     </listitem>
    </varlistentry>

    <varlistentry>
     <term>pz:recordfilter</term>
     <listitem>
      <para>
       Specifies a filter which allows Pazpar2 to only include
       records that meet a certain criteria in a result.
       Unmatched records  will be ignored.
       The filter takes the form name, name~value, or name=value, which
       will include only records with metadata element (name) that has the
       substring (~value) given, or matches exactly (=value).
       If value is omitted all records with the named metadata element
       present will be included.
      </para>
     </listitem>
    </varlistentry>
    
    <varlistentry>
     <term>pz:preferred</term>
     <listitem>
      <para>
       Specifies that a target is preferred, e.g. possible local, faster
       target. Using block=pref on show command will wait for all these
       targets to return records before releasing the block.
       If no target is preferred, the block=pref will identical to block=1,
       which release when one target has returned records.     
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term>pz:block_timeout</term>
     <listitem>
      <para>
       (Not yet implemented).
       Specifies the time for which a block should be released anyway.      
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term>pz:termlist_term_count</term>
     <listitem>
      <para>
       Specifies number of facet terms to be requested from the target. 
       The default is unspecified e.g. server-decided. Also see pz:facetmap.
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term>pz:termlist_term_factor</term>
     <listitem>
      <para>
       Specifies whether to use a factor for pazpar2 generated facets (1) or not (0). 
       When mixing locallly generated (by the downloaded (pz:maxrecs) samples) 
       facet with native (target-generated) facets, the later will dominated the dominate the facet list
       since they are generated based on the complete result set. 
       By scaling up the facet count using the ratio between total hit count and the sample size, 
       the total facet count can be approximated and thus better compared with native facets. 
       This is not enabled by default.
      </para>
     </listitem>
    </varlistentry>

    <varlistentry>
     <term>pz:facetmap:<replaceable>name</replaceable></term>
     <listitem>
      <para>
       Specifies that for field <replaceable>name</replaceable>, the target
       supports (native) facets. The value is the name of the
       field on the target.
      </para>
      <note>
       <para>
        At this point only Solr targets have been tested with this
        facility.
       </para>
      </note>
     </listitem>
    </varlistentry>

    <varlistentry id="limitmap">
     <term>pz:limitmap:<replaceable>name</replaceable></term>
     <listitem>
      <para>
       Specifies attributes for limiting a search to a field - using
       the limit parameter for search. It can be used to filter locally
       or remotely (search in a target). In some cases the mapping of 
       a field to a value is identical to an existing cclmap field; in
       other cases the field must be specified in a different way - for
       example to match a complete field (rather than parts of a subfield).
      </para>
      <para>
       The value of limitmap may have one of three forms: referral to
       an existing CCL field, a raw PQF string or a local limit. Leading string
       determines type; either <literal>ccl:</literal> for CCL field, 
       <literal>rpn:</literal> for PQF/RPN, or <literal>local:</literal>
       for filtering in Pazpar2. The local filtering may be followed
       by a field a metadata field (default is to use the name of the 
       limitmap itself).
      </para>
      <note>
       <para>
        The limitmap facility is supported for Pazpar2 version 1.6.0.
        Local filtering is supported in Pazpar2 1.6.6.
       </para>
      </note>
     </listitem>
    </varlistentry>

    <varlistentry id="pzurl">
     <term>pz:url</term>
     <listitem>
      <para>
       Specifies URL for the target and overrides the target ID.
      </para>
      <note>
       <para>
        <literal>pz:url</literal> is only recognized for
        Pazpar2 1.6.4 and later.
       </para>
      </note>
     </listitem>
    </varlistentry>

    <varlistentry id="pzsortmap">
     <term>pz:sortmap:<replaceable>field</replaceable></term>
     <listitem>
      <para>
       Specifies native sorting for a target where
       <replaceable>field</replaceable> is a sort criteria (see command
       show). The value has to components separated by colon: strategy and
       native-field. Strategy is one of <literal>z3950</literal>,
       <literal>type7</literal>, <literal>cql</literal>,
       <literal>sru11</literal>, or <literal>embed</literal>.
       The second component, native-field, is the field that is recognized
       by the target.
      </para>
      <note>
       <para>
        Only supported for Pazpar2 1.6.4 and later.
       </para>
      </note>
     </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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