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xmlxml-namespaceswell-formed

Is xml document with undeclared prefix well-formed?

For example I have following document:

<root>
    <prefix:element>

    </prefix:element>
</root>

As you can see, namespace with prefix name undeclared. Is this document is not well-formed?

From w3fools documentation:

A "Well Formed" XML document has correct XML syntax. The syntax rules:

  • XML documents must have a root element
  • XML elements must have a closing tag
  • XML tags are case sensitive
  • XML elements must be properly nested
  • XML attribute values must be quoted

...nothing about namespaces.

Solution

  • Namespaces in XML is a separate spec from XML 1.0 itself. The example document you give is well-formed XML 1.0 but is not namespace-well-formed according to the namespaces spec, and if you wanted to parse it you'd have to use a parser configured not to be namespace aware.