What is the difference between isolation domain and concurrency domain?

[stzn]

The term “isolation domain” is used to refer to an independent unit of isolation in Data Race Safety.
Swift 6 Concurrency Migration Guide

However, it seems that the term “concurrency domain” is used for the same concept in The Swift Programming Language (TSPL).
The Swift Programming Language - Concurrency

If they refer to the same concept, which term is correct?
If these terms are different, what is the difference between them?

[stzn]

And "concurrency context" as well.
https://developer.apple.com/documentation/swift/sendable

[mattmassicotte]

This is a really great observation. All these terms are equivalent.

@hborla do you have any opinions on which would be the most resonable to standardize around?

[stzn]

A similar discussion appears to be presented.
swiftlang/swift#79509 (comment)

[hborla]

Yeah, originally I was using "isolation domain", but I agree with Sima's comments in the other discussion that "concurrency domain" is probably more approachable, which is why I used that term in the educational notes. I'm leaning toward standardizing on "concurrency domain" and updating the migration guide to use that term instead of "isolation domain". Thoughts?

[stzn]

Thank you for the comment.

While "concurrency domain" is a valid term, "isolation domain" might be more intuitive since Swift already uses "isolation" terminology like actor isolation and isolated/nonisolated. Understanding the concept of "isolation" could help people better grasp the meaning of "isolation domain" over time.

I'm curious about why "concurrency domain" is considered a more approachable or readable term in the comment in the other discussion. Will "concurrency domain" provide a better entry point for learning concurrency?

[FranzBusch]

I personally also prefer isolation domains since as @stzn said isolation is spread everywhere in the language e.g. isolated parameters.

[heckj]

While "concurrency domain" does a good job implying there's a domain's that concurrency resides in, isolation domain has the benefit of reflecting the keywords that all use isolation, which gives it a solid link. I personally started mapping that back to the early async/await + actors talk at WWDC a few years back that used islands as a metaphor, which also made me think more of "isolation domain".

When it comes right down to it, if we refit to be consistent I don't think either term will be bad. Just feels like a smidge more of a lift to map "isolated and nonisolated" into that phrasing.

[hborla]

I'd also love to hear @amartini51 's thoughts