XQuery to translate characters

We needed a way to translate characters from one character set to another depending on an external web service. I made the following xquery module uoa.xq:

module namespace uoa = "http://www.tempurl.co.nz/xquery";

declare function uoa:convertString($inputString as xs:string, $translationSet as element()*) as xs:string {
        if (count($translationSet) = 0) then (: base case :)
           $inputString
 else (: recursion :)
           let $fromValue := data($translationSet[1]/translate_from)
           let $toValue := data($translationSet[1]/translate_to)
           let $updatedStr := fn:replace($inputString,$fromValue,$toValue)
           return uoa:convertString($updatedStr,remove($translationSet,1))
};

Declaring a translation set can be done with an XML file like translation.xml:

 
          A
          BB
        
 
          C
          DD
        

Then invoking this can be achieved with the following xquery:

import module namespace uoa="http://www.tempurl.co.nz/xquery" at "uoa.xq";

let $inputString := "AABBCCDD"
let $translationSet := doc("translation.xml")/translation_set/translation
let $outputString := uoa:convertString($inputString,$translationSet)

return

        {$inputString}
        
{$outputString}

This takes the input string and recursively iterates through the translation set (note that xquery is very functional and immutable variables mean that loops won't work!).