=  "Narrow your search" widget =

|| '''Date''' || 2012/09/11 ||
|| '''Contact(s)''' || François Prunayre ||
|| '''Last edited''' || 2012/09/11 ||
|| '''Status''' || Ongoing ||
|| '''Assigned to release''' || 2.9.x ||
|| '''Resources''' || Resource available ||

[[PageOutline(2-3,,inline)]]


== Overview ==

This proposal aims to provide a « Narrow your search » module aka as faceted search (http://en.wikipedia.org/wiki/Faceted_search). This module allows aggregation based on criteria (e.g. keywords, organization, dates, ...) with frequency for the current search. Output view could be a list (with link to add a specific criteria to the search) and optionnaly a tagcloud view (http://en.wikipedia.org/wiki/Tag_cloud).


On the client side, user interacts with facets using :
 * the facets summary used to select new filter
 * the facet breadcrumb which indicates which filter has been applied
and allows user to remove a filter.

Those 2 components are created and interact with search form and search results widgets.

A first implementation has been made on geocat.ch using the internal summary module in 2008. This proposal is using Lucene faceting module to compute the summary.

=== Proposal Type ===
 * '''Type''': GUI Change, LuceneSearcher
 * '''App''': !GeoNetwork
 * '''Module''': Search Interface

=== Links ===
 * '''Documents''':
  * example http://www.geocatalogue.fr/, http://www.geocat.ch
 * '''Email discussions''':
 * '''Other wiki discussions''':

=== Voting History ===
 * Vote proposed by X on Y, result was +/-n (m non-voting members).

----

== Motivations ==

 * Improve user search experience : facets help user to quickly refine search
 * Better performance : Lucene facet module using its own taxonomy index is faster than computing summary.
 * New way of presenting information : facet could be use to provide catalog indicators using charts (http://www.youtube.com/watch?v=ISEOKOq6t2Q&feature=plcp)


== Proposal == 

=== Faceted search widgets ===

TODO


=== Facet configuration ===

The facet configuration define which field in the index to use to compute the summary.
The configuration is stored in WEB-INF/config-summary.xml. For each facet configure an item with the following properties:
 * name: the name of the facet (ie. the tag name in the XML response)
 * plural: the plural for the name (ie. the parent tag of each facet values)
 * indexKey: the name of the field in the index
 * (optional) sortBy: the ordering for the facet. Defaults is by count.
 * (optional) sortOrder: asc or desc. Defaults is descendant.
 * (optional) max: the number of values to be returned for the facet. Defaults is 10.

When an item is modified or added, the index MUST be rebuild.

Configuration example:
{{{
<item name="keyword" plural="keywords" indexKey="keyword"/>

<item name="createDateYear" plural="createDateYears" indexKey="createDateYear"
				sortBy="value" sortOrder="asc" max="40"/>
}}}			

Facet configuration is loaded on startup. It could be reloaded from the administration panel using the reload configuration button.


=== Facet response ===

Facet summary is returned in the XML response. The response structure is the following:
{{{
<response>
  <summary count="4797" type="local">
    <keywords>
      <keyword count="1280" name="soil types"/>
      <keyword count="1003" name="geology"/>
      <keyword count="958" name="soils"/>
      <keyword count="894" name="soil classification"/>
      <keyword count="695" name="land use"/>
      <keyword count="609" name="topography"/>
      <keyword count="595" name="land suitability"/>
      <keyword count="550" name="land"/>
      <keyword count="508" name="physiography"/>
      <keyword count="507" name="crops"/>
    </keywords>
    <spatialRepresentationTypes>
      <spatialRepresentationType count="2641" name="grid"/>
      <spatialRepresentationType count="625" name="vector"/>
    </spatialRepresentationTypes>
  </summary>
  <metadata>
   ...
}}}

The summaryOnly=true parameter return only the summary without records.


=== Performance analysis ===


[[Image(geonetwork-test-on-lucene-faceting-module.png)]]

=== Changes ===

 * Lucene
  * Update to version 3.6.1
  * New dependency : lucene-facet 
 * LuceneSearcher.makeSummary()
 * Add an option to search services to only produce the summary
 * LuceneConfig
  * Summary configuration is part of LuceneConfig
  * Summary configuration could be reload dynamically when the LuceneConfig is reload.


=== Backwards Compatibility Issues ===

== Risks ==

== Participants ==
 * As above