This module provides functions for validating the DTD of XML documents represented as XmlTree.

Unlike other popular XML validation tools the validation process returns a list of errors instead of aborting after the first error was found.

Unlike validation of the document, the DTD branch is traversed four times:

• Validation of Notations
• Validation of Unparsed Entities
• Validation of Element declarations
• Validation of Attribute declarations

Removes doublicate declarations from the DTD, which first declaration is binding. This is the case for ATTLIST and ENTITY declarations.

• returns : A function that replaces the children of DOCTYPE nodes by a list where all multiple declarations are removed.

Validate a DTD.

• returns : a functions which takes the DTD subset of the XmlTree, checks if the DTD is valid and returns a list of errors