String Module

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Updated with Version 10: Renamed from Strings Module to String Module. The namespace URI has been updated as well.

This XQuery Module contains functions for string operations and computations.


All functions and errors in this module and errors are assigned to the namespace, which is statically bound to the string prefix.



Signatures string:levenshtein($string1 as xs:string, $string2 as xs:string) as xs:double
Summary Computes the Damerau-Levenshtein Distance for two strings and returns a double value (0.0 - 1.0). The returned value is computed as follows:
  • 1.0 – distance / max(length of strings)
  • 1.0 is returned if the strings are equal; 0.0 is returned if the strings are too different.
  • string:levenshtein("flower", "flower") returns 1
  • string:levenshtein("flower", "lewes") returns 0.5
  • In the following query, the input is first normalized (words are stemmed, converted to lower case, and diacritics are removed). It returns 1:
let $norm := ft:normalize(?, map { 'stemming': true() })
return string:levenshtein($norm("HOUSES"), $norm("house"))


Signatures string:soundex($string as xs:string) as xs:string
Summary Computes the Soundex value for the specified string. The algorithm can be used to find and index English words with similar pronouncation.
  • string:soundex("Michael") returns M240
  • string:soundex("OBrien") = string:soundex("O'Brien") returns true


Signatures string:cologne-phonetic($string as xs:string) as xs:string
Summary Computes the Kölner Phonetik value for the specified string. Similar to Soundex, the algorithm is used to find similarly pronounced words, but for the German language. As the first returned digit can be 0, the value is returned as string.
  • string:cologne-phonetic("Michael") returns 645
  • every $s in ("Mayr", "Maier", "Meier") satisfies string:cologne-phonetic($s) = "67" returns true


The functions in this section have been adopted from the obsolete Output Module.


Signatures string:format($format as xs:string, $items as item() ...) as xs:string
Summary Returns a formatted string. The remaining arguments specified by $items are applied to the $format string, according to Java’s printf syntax.
Errors format: The specified format is not valid.
  • string:format("%b", true()) returns true.
  • string:format("%06d", 256) returns 000256.
  • string:format("%e", 1234.5678) returns 1.234568e+03.


Signatures string:cr() as xs:string
Summary Returns a single carriage return character (


Signatures string:nl() as xs:string
Summary Returns a single newline character (


Signatures string:tab() as xs:string
Summary Returns a single tabulator character (	).


Version 10.0

The Module was introduced with Version 8.3. Functions were adopted from the obsolete Utility and Output Modules.