Python & XML

Types of Conformance

As with any specification, the primary reason for the XML specification’s existence is to hold documents against it and make sure they conform to the specification. If so, then the rules within the specification can be used in reading, transforming, or applying the document. However, we must remember that XML defines two things: syntax for document instances, and a way to define new language using XML. It also tells us that we can use the former without the latter, so it must define what it means to conform to the specification in both cases.

If a document uses the XML syntax but does not depend on a specific markup language defined using the means provided by the XML recommendation, it needs to be well-formed in order to conform with XML. This is a form of conformance introduced by XML rather than inherited from SGML. On the other hand, a document that declares that it uses a specific markup language defined by a DTD is said to be valid if it is both well-formed and the elements and character data are arranged in a way that complies with the rules given by the specified Document Type Definition.

The XML specification defines a collection of text to be an XML document if it is well-formed according to the rules of the specification. The term well-formed is widely used in XML, and it refers to a document that is syntactically acceptable. For example:

<?xml version="1.0"?>
<book>
  <title>Python and XML</title>
</book>

The preceding document is well-formed. That is, ...