OPML

Outline Processor Markup Language

http://www.opml.org/

"Standard" created by Dave Winer for representing an outline as XML. (OutLining)

Unfortunately it [seems](http://cww.evectors.it/itSItes/Blogs Directory/itEntDirectory/home?dir=14&rnd=413) an OPML document can't be validated.

• Validation seems like generally a "good thing", but should it be a deal-breaker?

Mark Pilgrim makes a case for out OutLining format which is mainly ASCII. Because everything in life should be PlainText. Sure, Python code is an outline, and my IDE takes advantage of that. But I don't always have my IDE (it's MsWindows-specific), and not all installations of EMacs have python-mode. Sometimes all I have is Note Pad. But Python code is plain text, so I can edit it in anything. All I have to do is keep track of spaces myself; the rest is just text. Simple. This is why I dislike outliners in general, and the OPML format in particular: they presume that my work is primarily an outline, secondarily text. OPML clearly expresses the hierarchical structure of the outline, but obfuscates (entity-encodes) all my actual content. This is exactly backwards.

• OML keeps the node-text bits readable/editable.

The InterOp format for Instant Outlining.

An alternative being explored is OTLML

another is OML

Some code for rendering to a Web Browser.