(Orbit author here) Wozniak is the pioneer, and like all in this space, we're heavily inspired by his work. Orbit is a vehicle for exploring some different ideas in this space. For instance, we're looking at how spaced repetition might be woven into a written form, like a book, so that authors can facilitate readers internalizing ideas deeply with relatively little extra effort. (see https://quantum.country for an example)

Are you familiar with Niklas Luhmann’s “zettelkasten” methods? Seems like there might be some fertile ground at the intersection of these two ideas...

Andy (the Orbit author) has his own very interesting Zettelkasten-like set of public notes. In this page, for example, he compares/contrasts his "Evergreen note" approach to a Zettles in a Zettlekasten: https://notes.andymatuschak.org/z4AX7pHAu5uUfmrq4K4zig9x8jmm...

Additionally, his system does have spaced repetition built-in, too:

"I’ve embedded a Spaced repetition memory system into my notes: The mnemonic medium can be extended to one’s personal notes. This has substantially changed the medium, but in ways I don’t yet understand very well."

I do not believe he has open-sourced his note taking system, but it is fun to browse around in; he presents a lot of interesting ideas, particularly if you're into this space.

> I do not believe he has open-sourced his note taking system

He is using Bear, you can find on youtube how he creates those notes.

Indeed. For example, org-mode can easily implement both a Zettelkasten and SRS. There are ready-made packages for both.

The schematics for the older versions of the SuperMemo algorithm (SM-2 and SM-5) have been published but they're quite old and any good reimplementation is actually a fork that fixes glaring deficiencies in the old algorithms.

The newest versions (SM-19) are proprietary and rely on a bunch of training data (they use some kind of ML) gathered from SuperMemo users (there is a way to get access to SuperMemo algorithm but you have to negotiate a license from memory). There is some rough outline of the algorithms on the SuperMemo wiki, but you couldn't reimplement it any more than you could reimplement Google Search given the Wikipedia description of PageRank.

> there is a way to get access to SuperMemo algorithm but you have to negotiate a license from memory

Well, SuperMemo may be of some help to the memory portion :-)

Is this public information? Where can I read more about SM-19?

Sorry I meant SM-18 (released in 2019, hence the confusion). But for completeness the only information available on SM-17 is one of two incredibly long articles written by Piotr Wozniak[1,2]. SM-18 is only a minor improvement over SM-17, with some changes to how difficulty is calculated[3].

[1]: https://supermemo.guru/wiki/Algorithm_SM-17 [2]: https://www.supermemo.com/en/articles/history [3]: https://supermemo.guru/wiki/Item_difficulty_in_Algorithm_SM-...