(identifier) provides a unique identifier for the element bearing the attribute.
(language) indicates the language of the element content using a tag generated
according to BCP 47
provides a base URI reference with which applications can resolve relative URI
references into absolute URI references.
signals an intention about how white space should be
managed by applications.
the processor should treat white space according to the
default XML white space handling rules
the processor should preserve unchanged any and all
white space in the source