Read/write to XML file in data folder

[arek1]

Thank you, I found it last night but one problem freeze me in place and I can't go forward.
My main goal is to create form where data are saved and read to/from XML. This form will be on one page, so I do not need plugin (because as I understand from Wiki plugin is displayed on every page). I created in my template folder somefile.php and create in it typical template (all working OK). Assign this template in Admin->Pages with one page.
Now if I put in this file code bellow (of course have correct xml file and so on) it read nothing.

Code:

$getdata = getXml(GSDATAOTHERPATH. $file . '.xml');
echo $getdata->node;

It point me to conclusion maybe it working only in plugin not in template files?
And second consideration: I'm still not sure where to put my XML file (but I was trying every place :-) ).
If using plugin and GSDATAOTHERPATH it is clear (in data/other/myxmlfile.xml) but if using template is it the same or GSDATAOTHERPATH point to different place?

Again thank you for your time :-)

Best wishes
ArekS