How add more chapter in chapter metadata xml - xquery

Question

A chapter-metadata.xml store in each book isbn folder(there are 100 isbn folder so there is 100 chapter-metadata.xml) which store in marklogic database server and chapter-metadata. Xml either contain data of one chapter or empty. If chapter-metadata.xml contain only one chapter information then I want to add more chapter information(my chapter infomation is common for all chapter) under chapter element with attribute and value of that chapter up to how many chapter store in book isbn folder(that I can fetch and store in a variable $chapter_sequence like ch001 ch002 ch003 ch004..) or if chapter-metadata.xml does not have any chaper information then it will create chapter element with attribute and value of chapter number and add my information, below I have put some xml structure if there is one chapter information and my information is from element keywordset
<?xml version="1.0" encoding="UTF-8" ?>
<chaptermetadata>
<bookisbn>isbn number</bookisbn>
<booktitle>Copyright</booktitle>
<chapter id="ch001"">
<keywordset>
<keyword role="primary">context</keyword>
<keyword role="secondary">Copyright</keyword>
<keyword role="tertiary">subject</keyword>
</keywordset>
</chapter>
</chaptermetadata>
I want like below:
<?xml version="1.0" encoding="UTF-8" ?>
<chaptermetadata>
<bookisbn>isbn number</bookisbn>
<booktitle>Copyright</booktitle>
<chapter id="ch001"">
<keywordset>
<keyword role="primary">context</keyword>
<keyword role="secondary">Copyright</keyword>
<keyword role="tertiary">subject</keyword>
</keywordset>
</chapter>
<chapter id="ch002"">
<keywordset>
<keyword role="primary">context</keyword>
<keyword role="secondary">Copyright</keyword>
<keyword role="tertiary">subject</keyword>
</keywordset>
</chapter>
so on to last chapter which I store in veriable
</chaptermetadata>
thanks,
raj

Answer 1

The question is hard to follow, but start with http://docs.marklogic.com/xdmp:directory and a FLWOR expression. Let's say you put this into a function. I'll handwave a few helper functions that you would also have to implement, but the function might look something like this:
declare function chaptermetadata($isbn as xs:string)
as element(chaptermetadata) {
<chaptermetadata>
{
<bookisbn>{ $isbn }</bookisbn>
<booktitle>{ title($isbn) }</booktitle>
for $chapter in xdmp:directory(isbn-uri($isbn), 'infinity')
return element { fn:node-name($chapter) } {
$chapter/#*,
$chapter/keywordset }
}
<chaptermetadata>
};
Now, this code won't help much unless you understand everything that it's doing so you can modify it to suit your needs. This is a variation on one of the XQuery use cases, so you might find helpful to work through and understand those: http://www.w3.org/TR/xquery-use-cases/