This experimental module is designed to allow for easy creation and
manipulation of OPML files. OPML files are most commonly used for the sharing
of blogrolls or subscriptions - an outlined list of what other blogs an
Internet blogger reads.

This is purely experimental at this point and has a few limitations. This
module may now support attributes in the <outline> element of an embedded
hierarchy, but these are limited to the following attributes: date_added,
date_downloaded, description, email, filename, htmlurl, keywords, text,
title, type, version, and xmlurl. Additionally, the following alternate
spellings are also supported: dateAdded, dateDownloaded, htmlUrl, and xmlUrl.