•[+] Other tools use itRadioland and numerous other utilities readily create and consume OPML files.
•[-] It's missing descriptions as a standard data elementFor example, it'd be nice to be able to create outlines of blog entries. Not nicely crowbarred into OPML.
6Create something new(2)My leading proposal is for a hierarchical RSS. Many of the same fields, plus a few more to support outline rendering (eg. expansion state).
•[+] Aim to create something fresh and useful, yet familiar and accessible
•Harder to manage dataRequires insertion/extraction processes, which can be cumbersome and obscure.
•Installation and portabilityPlatform limitations. More restrictive system requirements. Administration complexities.
•[+] More powerful functionality is possibleAllows for the development of more sophisticated features: User tracking, archiving, auditing, item reuse, access control.
4Outline data structures(6)What does an outline item consist of? What ways can items be related to one another, beside parent-child? How do you represent transclusion relationships?
•Subnodes collapsedDave's expansion state, but stored properly--as an item attribute.
•User-defined fields?Separate the outline node data structures from the outline item data structures. This would allow for multiple types of items. Some examples: contacts, web log entries, scheduled events, locations.
•Utility for content creation in personal web log sitesContent creation tool for creating dense, well-organized, easily maintained hierarchical lists of information.
•Personal information managementFor those who need online access to their PIM content.