ASX and XML are incompatible

I have been working with various playlist file formats as part of my internet radio project. This has involved creating XSPF playlists from XML sources and using XSLT to convert from XSPF to the alternative PLS and M3U formats.

According to the Simple ASX article on MSDN:​ an ASX file is an eXtensible Markup Language (XML)-based text file which references a Uniform Resource Locator (URL) for a piece of media content. Having read this I felt that ASX files ought fit neatly into my XML and XSLT based architecture. Only when implementing this,​ did I discover that ASX actually has quite limited compatibility with XML.