Full-Text Module
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This module extends the W3C Full Text Recommendation with some useful XQuery Functions: The index can be directly accessed, full-text results can be marked with additional elements, or the relevant parts can be extracted. Moreover, the score value, which is generated by the contains text
expression, can be explicitly requested from items. All functions are introduced with the ft:
prefix, which is linked to the http://www.basex.org/ft
namespace.
Contents
ft:search
Signatures | ft:search($node as node(), $text as xs:string) as text() |
Summary | Performs a full-text index request. |
Rules | This function performs an explicit full-text index request on the specified database node and returns all text nodes that contain the string $text . The index full-text options are used for searching, i.e., if the index terms were stemmed, the search string will be stemmed as well. |
Examples | The expression ft:search(., "QUERY") returns all text nodes of the currently opened database that contain the string "QUERY". |
Errors | BASX0002 is raised if the context item does not represent a database node. |
ft:mark
Signatures | ft:mark($nodes as node()*) as node()* ft:mark($nodes as node()*, $tag as xs:string) as node()* |
Summary | Marks results from a full-text index request. |
Rules | This function puts a marker element around the resulting $nodes of a full-text index request.The default tag name of the marker element is mark . An alternative tag name can be chosen via the optional $tag argument.Note that the XML node to be transformed must be an internal "database" node. The transform expression can be used to apply the method to a main-memory fragment (see example). |
Examples | The following query returns <XML><mark>hello</mark> world</XML> , if one text node of the database DB has the value "hello world":
|
Errors | BASX0002 is raised if the context item does not represent a database node. FOCA0002 is raised if $name is no valid QName. |
ft:extract
Signatures | ft:extract($nodes as node()*) as node()* ft:extract($nodes as node()*, $tag as xs:string) as node()* ft:extract($nodes as node()*, $tag as xs:string, $length as xs:integer) as node()* |
Summary | Extracts relevant parts of full-text results. |
Rules | This function extracts and returns relevant parts of full-text results. It puts a marker element around the resulting $nodes of a full-text index request and chops irrelevant sections of the result.The default tag name of the marker element is mark . An alternative tag name can be chosen via the optional $tag argument.The default length of the returned text is 150 characters. An alternative length can be specified via the optional $length argument. Note that the effective text length may differ from the specified text due to formatting and readibility issues. |
Examples | The following query may return <XML>...<b>hello</b>...<XML> if a text node of the database DB contains the string "hello world":
|
Errors | BASX0002 is raised if the context item does not represent a database node. FOCA0002 is raised if $name is no valid QName. |
ft:score
Signatures | ft:score($item as item()*) as xs:double* |
Summary | Returns the score of items. |
Rules | This function returns the score values (0.0 - 1.0) that have been attached to the specified items. 0 is returned if no score was attached. |
Examples | The expression ft:score('a' contains text 'a') returns the xs:double value 1 . |