"OPML an XML-based format that allows exchange of outline-structured information between applications running on different operating systems and environments.

The design goal is to have a transparently simple, self-documenting, extensible and human readable format that's capable of representing a wide variety of data that's easily browsed and edited. As the format evolves this goal will be preserved. It should be possible for a reasonably technical person to fully understand the format with a quick read of a single Web page."