I don't know if this will help your situation or not but this is the code
that we use to load our dataset URLs from an external XML file. We need to
do this because we test our app locally as a proxied app, but deploy it as a
SOLO app. A solo app requires the URLs to be relative. Having the URLs in
an external file allows us to swap out the URLs by changing that file. No
need to touch the code...



This is the code in "canvas"...

<dataset name="ds_paths" request="true" type="http" src="paths.xml" />

<dataset name="ds1"/>

<datapointer xpath="ds_paths:/paths/ds1">
  <method event="ondata">
    parent.ds1.setAttribute( 'src', this.getNodeText() );
  </method>
</datapointer>

<dataset name="ds2"/>

<datapointer xpath="ds_paths:/paths/ds2">
  <method event="ondata">
    parent.ds2.setAttribute( 'src', this.getNodeText() );
  </method>
</datapointer>


<dataset name="ds3"/>

<datapointer xpath="ds_paths:/paths/ds3">
  <method event="ondata">
    parent.ds3.setAttribute( 'src', this.getNodeText() );
  </method>
</datapointer>



The contents of paths.xml looks something like this...

<paths>
   <ds1>http://www.domain.com/dsservlet/getds1&lt;/ds1>
   <ds2>http://www.domain.com/dsservlet/getds2&lt;/ds2>
   <ds3>http://www.domain.com/dsservlet/getds3&lt;/ds3>
</paths>




Hmm... looking at the datapointer code above, it could
probably simplified a little too...

<datapointer xpath="ds_paths:/paths/ds1"
             ondata="parent.ds1.setAttribute('src',this.getNodeText())" />