XQuery/Tag Cloud

Counting Words thumb|Example of a tag cloud. A tag cloud (or weighted list in visual design) is a visual depiction of user-generated tags, or simply the word content of a site, typically used to describe the content of web sites. One method of creating a tag cloud is to create a list of the words in a document, count the number of occurrences of each word, and depict the more frequently occurring words with a larger font size than the words that occur less frequently. Counting the total number of words in a text object To get a feeling for one of the basic techniques, let's examine Jon Robie's code, which takes all of the text nodes in a document, strings them together, splits them into a sequence of "words" (tokenizing by whitespace, punctuation, or the 'nbsp' entity), and counts the number of resulting words: let $txt := string-join( $doc//text() , " ") return count(tokenize($txt,'(\s|[,.!:;]|[n][b][s][p][;])+')) Note that the string-join() function here takes an input sequence and returns a single string that is separated by single spaces (the second argument of string-join). If you want to see what this routine treats as a "word" in your document, use the following variation. let $txt := string-join( $doc//text() , " ") let $words := tokenize($txt,'(\s|[,.!:;]|[n][b][s][p][;])+') return <words count="{count($words)}"> { for $word in $words return <word>{$word}</word> } </words> Another variation is the word-count() function found at xqueryfunctions.com: declare function local:word-count( $arg as xs:string? ) as xs:integer { count(tokenize($arg, '\W+')[. != '']) } ; This version uses the \W+ regular expression (which matches non-alphabetical characters) to return word tokens. Counting Keywords Kurt Cagle suggested the following XQuery for counting keywords: declare namespace xqwb="http://xquery.wikibooks.org"; declare function xqwb:word-count($wordlist as element() ) as element() { <terms> {for $term in distinct-values($wordlist/term) let $term-count := count($wordlist/term[. = $term]) return <term count="{$term-count}">{$term}</term> } </terms> }; let $keywords := <keywords> <term>red</term> <term>green</term> <term>red</term> <term>blue</term> <term>violet</term> <term>red</term> <term>blue</term> <term>blue</term> <term>red</term> <term>orange</term> <term>green</term> <term>yellow</term> <term>indigo</term> <term>red</term> </keywords> let $result := xqwb:word-count($keywords) return $result This Returns the Following <terms> <term count="5">red</term> <term count="2">green</term> <term count="3">blue</term> <term count="1">violet</term> <term count="1">orange</term> <term count="1">yellow</term> <term count="1">indigo</term> </terms> Creating a Tag Cloud From this you can create a Tag Cloud or word density map such as the "Popular Tags" link on the flickr web site Flicker Popular Tags declare namespace xqwb="http://xquery.wikibooks.org"; declare option exist:serialize "method=xhtml media-type=text/html indent=yes"; declare function xqwb:word-count($wordlist as element() ) as element() { <terms> {for $term in distinct-values($wordlist/term) let $term-count := count($wordlist/term[. = $term]) return <term count="{$term-count}">{$term}</term> } </terms> }; let $keywords := <keywords> <term>red</term> <term>green</term> <term>red</term> <term>blue</term> <term>violet</term> <term>red</term> <term>blue</term> <term>blue</term> <term>red</term> <term>orange</term> <term>green</term> <term>yellow</term> <term>indigo</term> <term>red</term> </keywords> let $result := xqwb:word-count($keywords) let $total := count($keywords/term) let $scale := 20 return <div> { for $term in $result/term let $fontSize := round( $term/@count div $total * 100 * $scale) order by $term return <span style="font-size:{$fontSize}%">{string($term)} </span> } </div>