1) Well Formed XML documents are the one that meets all the well-formedness constraints
given in this specification.
XML
document are well formed if they are syntactically correct
i.e. An
XML document with correct syntax is called "Well Formed".
2) Valid XML A Well Formed XML is a valid
XML, when the well-formed XML document follows the rules (document structure
and rule) specified by the XML Schema or DTD.
An XML
document validated against a DTD, Schema
is "Well Formed" and "Valid".
Valid XML
document is implicitly well-formed, but well-formed may not be valid
3) Broken XML documents are simply those
which fail to follow the rules required for a document to be either well-formed
or valid.
Basic rules of syntax
1) Every open tag must be closed.
2) The open tag must exactly match the closing tag: XML is case-sensitive.
3) All elements must be embedded within a single root element.
4) Child tags must be closed before parent tags.
5) A well-formed document has correct XML tag syntax, but the elements might be invalid for the specified document type.
