XML tools enforce XML syntax. XML syntax is very similar to HTML syntax, except, like XHTML, the syntax is strictly enforced. The syntax is:
Tags are enclosed within angle brackets, for example, <para>
Opening tags must be paired with closing tags, for example, <para>Sentence</para>
Opening and closing tags must be nested correctly, for example, the following example is well formedCopy
The following example is not well formedCopy
If these syntax rules are followed, the XML document is said to be well formed. That does not mean, however, that the tags in the XML document are necessarily the ones defined in the associated WSDL. If, for example, the WSDL defines <para>, an XML document that uses <Para> would cause an error because "Para" is not defined in the WSDL. When an XML document is well formed and the tags it uses conform to tags defined in the WSDL, the document is said to be valid. Product Advertising API responses always contain valid XML.