[colllectorof]

ECS (which I have not used) sounds a lot like Traits. The name and core concepts for Traits were defined in 2003 in an ECOOP paper [1]. I think traits were first implemented by Squeak Smalltalk in 2005.

[1] http://scg.unibe.ch/archive/papers/Scha03aTraits.pdf

[meheleventyone]

Very similar although in an ECS the relationship is backwards, Entities get behaviour based on what data they contain rather than getting behaviour from traits and needing to add state to make them work.

The ECS approach can lead to some confusing things like adding a component to an Entity and having strange behaviour result as a system the programmer didn’t expect to be triggered is run. This can lead to systems having quite complex definitions based not just on the components the system needs to run but also on the components that shouldn’t be present and so on.