need info on leaf nodes, attributes & overlay xml

Hi,
I'm a newbie to use expat parser and ofcourse new to XML.
I need some general clarifications.

Say, I have a XML file as,
                     <hostName>
                              <defaultValue>value</defaultValue>
                              <description>
                                      <shortDescr>Hostname identifies the
NE</shortDescr>
                                      <longDescr>long descr of
Hostname</longDescr>
                              </description>

                              <dataType>string</dataType>

                              <operations>set,delete</operations>

               </hostName>

1. Here, Is it possible to have description, datatype, operations as
attributes
    in the DOM tree generated from the parser, instead of as sub nodes of
"hostName".

2. Is there anyway to overlay XML on a tree.
    I know that expat parser doesnt support DTD. But is there anyother
options.

Please post your comments on this. Would be helpful for me to proceed
further.

Thanks
Senthil