What is XML

Extensible Markup Language (XML) defines a set of rules for encoding documents in a format that is both human-readable and machine-readable.

The following shows a sample XML document:

<?xml version="1.0" encoding="UTF-8"?>
<!-- A sample XML document -->
<nutrition>
<daily-values total=2000>
    <total-fat units="g">65</total-fat>
    <saturated-fat units="g">20</saturated-fat>
    <cholesterol units="mg">300</cholesterol>
    <sodium units="mg">2400</sodium>
    <carb units="g">300</carb>
    <fiber units="g">25</fiber>
    <protein units="g">50</protein>
</daily-values>
<food>
    <name>Avocado Dip</name>
    <mfr>Sunnydale</mfr>
    <serving units="g">29</serving>
    <calories total="110" fat="100">
    <total-fat>11</total-fat>
    <saturated-fat>3</saturated-fat>
    <cholesterol>5</cholesterol>
</food>
<food>
    <name>Truffles, Dark Chocolate</name>
    <mfr>Lyndon's</mfr>
    <serving units="g">39</serving>
    <calories total="220" fat="170"/>
    <total-fat>19</total-fat>
    <saturated-fat>14</saturated-fat>
    <cholesterol>25</cholesterol>
</food>
</nutrition>

This document consists of the <nutrition> tag followed by the <daily-values> and <food> elements. The elements contain other elements which can appear multiple times.

In general, an element contains attribute and text (value) content. For example:

<book category=fiction>Harry Potter<\book>

Here, fiction is the attribute and Harry Potter is the text content.

In order to take the content of a worksheet and produce an XML document, a relationship needs to be formed between the cell values on the worksheet and the XML elements of the document. This relationship needs to consider that elements can contain a set of sub elements.