[mercurial]

If you're doing low-level anything, it's usually because you're interested in the "exhaustive detail". This is quite confusing.

> Also as a result, Unison has a simple story for serialization and sharing of arbitrary terms, including functions. Two Unison nodes may freely exchange data and functions—when sending a value, each states the set of hashes that value depends on, and the receiving node requests transmission of any hashes it doesn’t already know about. Using nameless, content-based hashes for references sidesteps complexities that arise due to the possibility that sender and receiver may each have different notions of what a particular symbol means (because they have different versions of some libraries, say).

Yeah, I can see how this is going to solve the problem of persistence and networking once and for all. Or not. As for sidestepping the problem of having different versions of the same library on different nodes and serializing data, that's going to work fine until the first rename, or when node A with version 1 of the library sends a data structure with half the fields understood by version 2 of the library on node B...

[sixbrx]

He addresses this issue - see the part about using hashes for everything so neither names nor lib versions matter, only the contents do, identified by hashes.