[xquery-talk] Changing the content of an XML document

John Snelson john.snelson at oracle.com
Tue Sep 2 12:02:18 PDT 2008

Hi Georg,

The identity transform will work, and is essentially the same as the 
transformation function that Wolfgang suggests. However I think a 
transform expression is easier to understand if eXist supports XQuery 

copy $a := $tree
modify replace value of node $a//subnode with
   if($condition) then "some text" else "some other text"
return $a


Christian Schlaefcke wrote:
> Hi Georg,
> take a look at this thread:
> http://www.stylusstudio.com/xquerytalk/200808/002828.html
> I had a similar problem exept I wanted to delete certain nodes instead of
> replacing them.
> Espacially the "identity transform"
> (http://en.wikipedia.org/wiki/Identity_transform) hint was very helpful
> and it sounds as it could help you with your problem too.
> Best regards,
> Christian
>>> Wolfgang [mailto:wolfgang at exist-db.org] wrote:
>>>> This means, in the script I load the XML file into a
>>>> local variable using the doc() function and return the result to the
>>>> client.
>>>  >
>>>  > But now, occationally some of the content of the file has
>>> to be altered.
>>> I'm not sure I completely understand the question. Is the document
>>> stored in the db or do you load it from the filesystem? And
>>> do you only
>>> need to temporarily change some content of that file (in which case I
>>> would probably call an XSLT) or permanently (use XQuery
>>> update extensions)?
>> Actually I can reduce my question to the following: Assuming I have a
>> variable which stores a node-tree like that
>> let $tree :=
>>   <node>
>>     <subnode>
>>       some text
>>     </subnode>
>>   </node>
>> In reality $tree is the entire XML file which I want to send back to the
>> client. Now, depending on some conditions I want to change the content
>> of <subnode> "some text" to "some other text", before sending it. I
>> don't actually want to alter the file in the database, just the message
>> that I'm sending.
>> If I placed the XML-file inside the script, I would write something like
>> <node>
>>   <subnode>
>>   {
>>     if ($condition)
>>     then "some text"
>>     else "some other text"
>>   }
>>   </subnode>
>> </node>
>> But since I have a couple of not too small XML files I fear that this
>> will get a bit overcrwoded.
>> Do you understand what I mean?
>> Best,
>> Georg
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John Snelson, Oracle Corporation            http://snelson.org.uk/john
Berkeley DB XML:            http://oracle.com/database/berkeley-db/xml
XQilla:                                  http://xqilla.sourceforge.net

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