well-formed and valid XML difference

[Rr Kumaran]

Hi All,

What is the difference between well-formed and valid XML ?

Thanks & Regards,
Kumar.

[Lasse Koskela]

Well-formedness means that your XML structure is correct, you're not using illegal characters, etc. For example, the following document is not well-formed because the elements are not contained properly:

<root>
    <foo>
        just an
    <bar>
    </foo>
        example
    </bar>
</root>

The validity of an XML document, however, is about the XML document complying with a given DTD or XML Schema document which describes what kind of tags are allowed, in what order, how many of them, what other elements can they contain, etc.