XML Question when using DataView.Sort

[NJCI]

I have two questions:
1) Is my XML format correct?
<TableName>
___<MachineName>
______<Process>
________<Material>
________</Material>
______</Process>
___</MachineName>
</TableName>

(Used _ for tabs )
2) If I have Multiple <MachineName> level items, how do I use DataView.Sort to search on the <Material> based on the <MachineName>? (I had the files split by MachineName, but then I need to combine to one file. It worked before, but now it is giving me index errors and saying there is no column by the <TableName>)

Any help would be appreciated.