Unless you have a specific reason otherwise, the following is the One True Spec:
XSPF version 1 (November, 2006)
For historical reasons, you may find the following two versions of the spec useful.
trackList
may be empty.extension
added.date
changed from ISO 8601 to xsd:dateTime.version
incremented.Because it is easy to make mistakes, those who create XSPF documents should check their output against a validator.