and ''trackNum'' and your XSPF will be fine.
== Absolute vs. relative URIs in key
The attributes ''rel'' (<meta> and <link>) and ''application'' (<extension>)
are by XSPF v1 specification allowed to hold relative URIs. For example this
=== Ignore in non-leaf elements ===
Whitespace in elements only holding child elements but no text
must be ignored.
* You can use IPv6 host part URIs in XSPF v1
can use a RFC 3986 parser for your XSPF v1 implementation
= Errata =
It also reads "xspf:playlist elements MAY contain exactly one" which
does not make sense for the content of an element and can be safely ignored.