I have a xml file with data in it, Can I assume the data is in the exact form of the logical structure of the database? So if I start from the top of the document, I should be able to highlight all the important columns in the database, is this correct?
No, the structure actually is defined in the .dtd file.
Your .xml file contains only the data.
If the data u give in .xml doesn't match ut .dtd, the database wont be a valid one. So, if u want to know all important columns of the database, see the .dtd file.
That gives u the exact structure.