This is a placeholder for a namespace document that permits
dereferencing the Timed Text (TT) Authoring Format V1.0
Distribution Format Exchange Profile namespace URIs:

http://www.w3.org/ns/ttml
http://www.w3.org/ns/ttml#styling
http://www.w3.org/ns/ttml#styling-extension
http://www.w3.org/ns/ttml#metadata
http://www.w3.org/ns/ttml#metadata-extension
http://www.w3.org/ns/ttml#parameter
http://www.w3.org/ns/ttml#parameter-extension

This namespace document is expected to be replaced by a
W3C XML Schema document.