Search engine adapters

Revision as of 21:32, 17 November 2007 by Valery Fremaux (talk | contribs)

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The global search engine of Moodle, available as experimental feature till the Moodle 1.9 release, allows plugin new document types for being searched and indexed by the Lucene indexer.

Each module or block should have an adapter written to wrap the plugin's internal data model to a searchable document. The actual implementation allows a module to provide the search engine with a set of virtual documents. The search engine will index the text content of these documents, recording sufficiant data to access back the exact context in which it was appearing (i.e, access URL, course context, etc.).

Virtual documents are defined as subclasses of the SearchDocument class. Only the constructor of the subclass must be written in order to map an input record to an internal document definition.

The goals of the adapter are :

  • extract all virtual documents from the module data model and give them to the indexer (index first construction) through an iterator.
  • extract a single document for index update
  • provide sufficiant information for index delete of obsolete content
  • define the access URL that will access back the resource
  • define the access check algorithm so that the user will only access resources he is allowed to

Adapters for modules and blocks

Any adapter for a module or a block must reside in the
/search/documents
subdirectory, and will be named such as
<module>_document.php
.

Search defines

Each searchable module should add both following defines in /search/lib.php :

define('SEARCH_TYPE_<MODULE>', '<module>');
define('PATH_FOR_SEARCH_TYPE_<MODULE>', 'mod/<module>');

or

define('SEARCH_TYPE_<BLOCK>', '<block>');
define('PATH_FOR_SEARCH_TYPE_<BLOCK>', 'blocks/<block>');

Constructor

The constructor of the SearchDocument class has the following signature :

public function __construct(&$doc, &$data, $course_id, $group_id, $user_id, $path)

where :

  • &$doc is a reference onto a PHP object that should provide the fields :
    • docid : the id of the document, as suitable for reconstructing the access URL.
    • documenttype : in general, the name of the module itself
    • itemtype : a subclassifier, if the module provides more than one virtual document to the search engine.
    • contextid : the context object id that should be considered when checking accessor's capabilities
    • title : the title string to appear in search results as a caption
    • author : if the author is known, the user id (mdl_user.id) representing the author.
    • contents : a text bulk from the document content, filtered out from any formatting attributes or tags
    • url : the document url, that will be constructed by the adapter to access back the resource
    • date : usually the date when the resource was created
  • $data is a reference onto a contextual metadata object that will be serialized among with the record, but will not be used as searchable content


Physical document adapters