xsi:noNamespaceSchemaLocation No Namespace Schema Location

A pseudo-attribute some processors use to point to the location of the Tag Set’s XSD file. Cannot be used with DTDs (that is, with a document that contains a DOCTYPE Declaration pointing to a DTD).
OPTIONAL on elements: <book>, <book-part-wrapper>
Value Meaning
Text, numbers, or special characters File location of the XSD driver file.
Restriction @xsi:noNamespaceSchemaLocation is an optional attribute; there is no default.