Hi Shiv,
If you are entering strings directly into the "v" node ofa cell, use inline string element. Else, make a SharedString.xml file which will store all the unique strings, and enter the indexes of those stringsin the "v" nodes of a cell, an dalso set the type t="s" for the cell..
Btw.. you need not write so much XML with the help of the new SDK. Use the classes of the new SDK to generate the logical representations of workbook, worksheet, and write the data into the objects programatically.
-Regards,
nkchennai