The Fishbowl: To allow the format to be flexible and extensible, OPML producers can add arbitrary attributes to outline elements. While types and attributes are arbitrary, the specification does not provide implementors a mechanism for finding out the meaning of either.
http://fishbowl.pastiche.org/2005/10/02/whats_wrong_with_opml
Randy: Definately a major failing of OPML. Further, it's amazing to me that these authors continue to miss pointing out that there is no specification for the current version of OPML (1.1) and continue to point to the old spec.
Sounds like a feature request. Embed sounds ;-)
Randy