I posted this a few years ago, asking why there isn't a decent and flexible collaborative outliner like "Google Trees":

https://news.ycombinator.com/item?id=20425970

The thing that's missing from "Google Docs" is a decent collaborative outliner called "Google Trees", that does to "NLS" and "Frontier" what "Google Sheets" did to "VisiCalc" and "Excel".
And I don't mean "Google Wave", I mean a truly collaborative extensible visually programmable spreadsheet-like outliner with expressions, constraints, absolute and relative xpath-like addressing, and scripting like Google Sheets, but with a tree instead of a grid. That eats drinks scripts and shits JSON and XML or any other structured data.

Of course you should be able to link and embed outlines in spreadsheets, and spreadsheets in outlines, but "Google Maps" should also be invited to the party (along with its plus-one, "Google Mind Maps").

It should be like the collaborative outliner Douglass Englebart envisioned and implemented in his epic demo of NLS:

https://www.youtube.com/watch?v=yJDv-zdhzMY&t=8m49s

Engelbart also showed how to embed lists and outlines in maps:

https://www.youtube.com/watch?v=yJDv-zdhzMY&t=15m39s

Dave Winer, the inventor of RSS and founder of UserLand Software, originally developed a wonderful outliner on the Mac originally called "ThinkTank" and then "MORE", which later evolved into the "Frontier" programming language, and ultimately the "Radio Free Userland" desktop blogging and RSS syndication tool.

https://en.wikipedia.org/wiki/Dave_Winer

https://en.wikipedia.org/wiki/UserLand_Software

More was great because it had a well designed user interface and feature set with fluid "fahrvergnügen" that made it really easy to use with the keyboard as well as the mouse. It could also render your outlines as all kinds of nicely formatted and stylized charts and presentations. And it had a lot of powerful features you usually don't see in today's generic outliners.

https://en.wikipedia.org/wiki/MORE_(application)

>MORE is an outline processor application that was created for the Macintosh in 1986 by software developer Dave Winer and that was not ported to any other platforms. An earlier outliner, ThinkTank, was developed by Winer, his brother Peter, and Doug Baron. The outlines could be formatted with different layouts, colors, and shapes. Outline "nodes" could include pictures and graphics.

>Functions in these outliners included:

>Appending notes, comments, rough drafts of sentences and paragraphs under some topics

>Assembling various low-level topics and creating a new topic to group them under

>Deleting duplicate topics

>Demoting a topic to become a subtopic under some other topic

>Disassembling a grouping that does not work, parceling its subtopics out among various other topics

>Dividing one topic into its component subtopics

>Dragging to rearrange the order of topics

>Making a hierarchical list of topics

>Merging related topics

>Promoting a subtopic to the level of a topic

After the success of MORE, he went on to develop a scripting language whose syntax (for both code and data) was an outline. Kind of like Lisp with open/close triangles instead of parens! It had one of the most comprehensive implementation of Apple Events client and server support of any Mac application, and was really useful for automating other Mac apps, earlier and in many ways better than AppleScript.

https://en.wikipedia.org/wiki/UserLand_Software#Frontier

http://frontier.userland.com/

Then XML came along, and he integrated support for XML into the outliner and programming language, and used Frontier to build "Aretha", "Manila", and "Radio Userland".

http://manila.userland.com/

http://radio.userland.com/

He used Frontier to build a fully programmable blogging and podcasting platform, with a dynamic HTTP server, a static HTML generator, structured XML editing, RSS publication and syndication, XML-RPC client and server, OPML import and export, and much more.

He basically invented and pioneered outliners, RSS, OPML, XML-RPC, blogging and podcasting along the way.

>UserLand's first product release of April 1989 was UserLand IPC, a developer tool for interprocess communication that was intended to evolve into a cross-platform RPC tool. In January 1992 UserLand released version 1.0 of Frontier, a scripting environment for the Macintosh which included an object database and a scripting language named UserTalk. At the time of its original release, Frontier was the only system-level scripting environment for the Macintosh, but Apple was working on its own scripting language, AppleScript, and started bundling it with the MacOS 7 system software. As a consequence, most Macintosh scripting work came to be done in the less powerful, but free, scripting language provided by Apple.

>UserLand responded to Applescript by re-positioning Frontier as a Web development environment, distributing the software free of charge with the "Aretha" release of May 1995. In late 1996, Frontier 4.1 had become "an integrated development environment that lends itself to the creation and maintenance of Web sites and management of Web pages sans much busywork," and by the time Frontier 4.2 was released in January 1997, the software was firmly established in the realms of website management and CGI scripting, allowing users to "taste the power of large-scale database publishing with free software."

https://en.wikipedia.org/wiki/RSS

https://en.wikipedia.org/wiki/OPML

https://en.wikipedia.org/wiki/XML-RPC