A Valid XML document is a Well-Formed XML document that also conforms to the rules of a schema that defines the legal elements of an XML document. The schema type can be: XML Schema, Relax NG (full or compact syntax), Schematron, Document Type Definition (DTD), or Namespace-based Validation Dispatching Language (NVDL).
The purpose of the schema is to define the legal building blocks of an XML document. It defines the document structure with a list of legal elements.
The
Validate function ensures that your document is compliant with the rules
defined by an associated DTD, XML Schema, Relax NG, or Schematron schema. XML Schema or Relax
NG Schema can embed Schematron rules. For Schematron validations you can select the validation
phase.