[xml] Memory requirement "heuristics" for libxml?

["Martin B." <0xCDCDCDCD gmx at>]

Hi!

Are there any guidelines as to what memory requirements are to be 
expected when reading a xml file with xmlReadFile?
That is, given a simple xml file (no namespaces and such stuff) with no 
text nodes, how much memory do the data structures take, compared to the 
file on disk?

Simple Example

<?xml version="1.0" encoding="UTF-8"?>
<Configuration v="x.y">
  <Item id="..." value="..."/>
  <Item id="..." value="...">
    <SubItem id="..." value="..." comment="..."/>
    [...]
  </Item>
  [...]
</Configuration >

Given a file with this structure, how much memory will be allocated 
compared to the file-size when reading the file with xmlReadFile? 
More/Less/equal? Depends - on what?

thanks!
- Martin