5 ms·

> offline-first development, where concurrent timelines don’t really have any limit on the length of their diverging histories Is there really great utility in

> offline-first development, where concurrent timelines don’t really have any limit on the length of their diverging histories Is there really great utility in automatically merging wildly divergent documents? Being able to send your queued changes and agree on a new state of the world is lovely, but for most of the circumstances I can imagine the ideal new "state of the world" is "please fix this merge conflict", not "here's my best guess at a reasonable state based on the semantics of some data structure." Maybe it's domain specific. Maybe in code you want merge conflicts and in some kinds of rich text docs you just want a best-guess auto-merge. Even then, though, I think it would depend a lot on what the document is for. Maybe blog posts and company culture docs should get auto-merge and legal contracts should get merge conflicts.

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kybernetikos 8y ago
I agree with this. The correct way of resolving conflicts is different depending on both the semantics of the document and the context in which the conflict arose. For example, I think the CRDT approach is probably applicable to most examples of interactive editing, where incorrect conflict resolutions will happen near a point of focus for one of the editors and can be quickly and easily resolved. If you have wildly divergent documents however (again depending on the document type itself), this is not really the same case, and it's much more likely that a human will need to create a resolved document by consulting the two parent documents.
kd5bjo 8y ago
Lots of people collaborate by emailing files to each other, and do version control by saving under a different filename every time. Using CRDTs as an on-disk file format can make these workflows less annoying, by working with changes instead of differences: the same advantage that Git's 3-way merge algorithm has over Subversion's 2-way merge.
archagon 8y ago
Yes, there is great utility in this approach! For one, most concurrent text editing, rich or not, is actually quite easy to merge in 99% of cases. But even that aside, when you have data structures or document formats that don't ever have to resolve conflicts—or, more accurately, when conflict resolution becomes something that's naturally done in app-space, on the edges, and not as part of the network layer—then you open up the possibility of offline-capable, collaborative apps that require zero coordination between nodes. A node with changes only has to deliver their content to interested servers and peers, not engage in lengthy conversations about who has the definitive version, whether somebody has to revert, etc. You could build a Google Docs clone that synced entirely over Dropbox! And in any case, the "merge" part would still be up to the app. The data structures will always be able to merge, sure, but the app could still throw up a dialog box on wildly divergent changes saying, "Hey, some crazy stuff happened here—want to look it over and commit manually?" (Where "commit" means generating new changes to overwrite any undesired changes, since it's not possible to literally undo.) You could argue that we've simply implemented ad-hoc coordination protocols in the app layer at that point, but IMO, that's exactly where they belong in cases where there's no authoritative store for your data. (Which is really the case with mobile, offline-first development.)

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kybernetikos 8y ago

I agree with this. The correct way of resolving conflicts is different depending on both the semantics of the document and the context in which the conflict arose. For example, I think the CRDT approach is probably applicable to most examples of interactive editing, where incorrect conflict resolutions will happen near a point of focus for one of the editors and can be quickly and easily resolved. If you have wildly divergent documents however (again depending on the document type itself), this is not really the same case, and it's much more likely that a human will need to create a resolved document by consulting the two parent documents.

kd5bjo 8y ago

Lots of people collaborate by emailing files to each other, and do version control by saving under a different filename every time. Using CRDTs as an on-disk file format can make these workflows less annoying, by working with changes instead of differences: the same advantage that Git's 3-way merge algorithm has over Subversion's 2-way merge.

archagon 8y ago

Yes, there is great utility in this approach! For one, most concurrent text editing, rich or not, is actually quite easy to merge in 99% of cases. But even that aside, when you have data structures or document formats that don't ever have to resolve conflicts—or, more accurately, when conflict resolution becomes something that's naturally done in app-space, on the edges, and not as part of the network layer—then you open up the possibility of offline-capable, collaborative apps that require zero coordination between nodes. A node with changes only has to deliver their content to interested servers and peers, not engage in lengthy conversations about who has the definitive version, whether somebody has to revert, etc. You could build a Google Docs clone that synced entirely over Dropbox! And in any case, the "merge" part would still be up to the app. The data structures will always be able to merge, sure, but the app could still throw up a dialog box on wildly divergent changes saying, "Hey, some crazy stuff happened here—want to look it over and commit manually?" (Where "commit" means generating new changes to overwrite any undesired changes, since it's not possible to literally undo.) You could argue that we've simply implemented ad-hoc coordination protocols in the app layer at that point, but IMO, that's exactly where they belong in cases where there's no authoritative store for your data. (Which is really the case with mobile, offline-first development.)