Represent the purchase order XML document of Question 1 in JSON and YAML. Contrast the three representations against each other.

Question 1

Consider our purchase order administration example from Chapter 3. Remember, a purchase order can have multiple purchase order lines, each corresponding to a particular product. A purchase order is also assigned to exactly one supplier. Develop a DTD and XML Schema for a purchase order and contrast both. Work out an example of an XML purchase order document with four purchase order lines. Illustrate how XPath can be used to retrieve specific elements of this purchase order.