[SOLVED] Xquery: How to extract out info from an REF/ID

Xquery: How to extract out info from an REF/ID

In my xml i have a number of IDs and REF attributes.

Simplified under:

<library>
 <book ID="123">
   <author ref="33"></author>
   <Info>Vulpes Vulpes, Canis Lupus</info>
   <about>Programming</about>
 </book>

 <author ID="33">
  <firstname>John</firstname>
  <lastname>McLovin</lastname>
 </author>
</library>

So I want to use a Xquery to extract out the info about the author, using the REF attribute under book.

for $x in library/book 
where $x/about = "programming"
return data ($x/library/book/author/@ref)

With this method i extract the refnumber 33. But I want the data that ref="33" points to, which is located under ID="33". I would like firstname and lastname as result.

Is this possible? If not like this, how is it possible?

Solution

for $x in library/book 
where $x/about = "Programming"
return data (library/author[@ID=$x/author/@ref])