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Frequently asked questions
Why is it called salsa?
I like salsa! Don't you?! Well, ok, there's a bit more to it. The underlying algorithm for figuring out which bits of code need to be re-executed after any given change is based on the algorithm used in rustc. Michael Woerister and I first described the rustc algorithm in terms of two colors, red and green, and hence we called it the "red-green algorithm". This made me think of the New Mexico State Question --- "Red or green?" --- which refers to chile (salsa). Although this version no longer uses colors (we borrowed revision counters from Glimmer, instead), I still like the name.
What is the relationship between salsa and an Entity-Component System (ECS)?
You may have noticed that Salsa "feels" a lot like an ECS in some ways. That's true -- Salsa's queries are a bit like components (and the keys to the queries are a bit like entities). But there is one big difference: ECS is -- at its heart -- a mutable system. You can get or set a component of some entity whenever you like. In contrast, salsa's queries define "derived values" via pure computations.
Partly as a consequence, ECS doesn't handle incremental updates for you. When you update some component of some entity, you have to ensure that other entities' components are updated appropriately.
Finally, ECS offers interesting metadata and "aspect-like" facilities, such as iterating over all entities that share certain components. Salsa has no analogue to that.