how to do this?

Hi,
i am a XML newbie and need help on the following:
for a GIS application, i need to design an interface that is as follows:
the user by means of an graphical interface(designed using javascript and HTML) selects a map and its corresponding data files.
now an XML file is to be defined that stores the data chosen by the user. this XML file is then transmitted to a server which performs the required processing to display the final map.
i want to know how such an XML file can be defined?
say for example, the user selects the map of USA, an text file containing the population of every state of USA and selects that for each range of data, a color is chosen. can i use like this:

<userselection>
<map>......</map>
<data>.......</data>
<color>........
........
</color>
</userselection>

this XML file should allow any file to be chosen. a servlet on the server-side gets this XML and extracts the required sata values.
thanks in advance

I suspect this is a homework question .. but if not, have
a look at www.opengis.org