[xquery-talk] adding or modifing an attribute

[Michael Kay]

In the absence of XQuery Updates, this kind of problem is rather tedious to
solve in XQuery, at least in comparison with the XSLT solution. 

You basically need to write a recursive function that is called to process
each node in the tree, and that calls itself to process its children.
Something like this:

declare function local:copy-and-change($nodes as node()*) as node()* {
for $in in $nodes return
  typeswitch ($in) {
  case element(name):
    <name> {
         @* except @average,
         attribute average {90},
         local:copy-and-change(child::node())
    } </name>
  case element():
    element {node-name($in)} {
         @*,
         local:copy-and-change(child::node())   
    }
  default:
    $in
}

local:copy-and-change(/*)

Note that this code will drop any namespaces that aren't used in element and
attribute names - don't use it if your document has namespace-sensitive
content such as xsi:type attributes. (I don't know of any general answer to
that problem.)

Michael Kay
http://www.saxonica.com/

> -----Original Message-----
> From: talk-bounces at x-query.com 
> [mailto:talk-bounces at x-query.com] On Behalf Of Sam Carleton
> Sent: 04 June 2008 17:03
> To: talk at x-query.com
> Subject: [xquery-talk] adding or modifing an attribute
> 
> I have worked with DOM, SAX, XSLT, and XPath in the past and 
> am now working with a framework that has XQuery.  The task at 
> hand is very simple, change (or add if not present) an 
> attribute to one element in an XML document:
> 
> Example: If the name element has an average attribute, change 
> it to 93, otherwise create it and set it to 93
> input:
> 
> <root>
>  <students>
>    <name value="scott"/>
>  </students>
> </root>
> 
> or
> 
> <root>
>  <students>
>    <name value="scott" average="90"/>
>  </students>
> </root>
> 
> output:
> 
> <root>
>  <students>
>    <name value="scott" average="93"/>
>  </students>
> </root>
> 
> How might I do this with XQuery?  The framework I am using is 
> Trolltech's Qt which is a C++ framework.  I am under the 
> impression I am going to have to load the XML document into 
> memory, execute the XQuery query on it that will result in a 
> new XML document that I will then save over the original XML 
> file, is that correct?  I can figure out the Qt stuff, the 
> real question is how would I put together a query to make 
> this change in XQuery?
> 
> Sam
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