"Message" vs "Event"

[Liam19]

This view might not be shared by many, but I was very surprised at the changes to events and observers in 0.17. IMO, the names are the wrong way around. In most contexts, a message implies directed communication - something intentionally sent to a specific recipient or group. An event, on the other hand, describes something that happens in the world, independent of who’s listening.

I just wanted to share my thoughts and maybe understand the reasoning for this naming scheme.

[Chris4942]

I'm not a maintainer, just another user, but here's my guess as to why it's called that:

• In general, queue services (e.g. AWS SQS) use the term message to refer to messages that will be eventually handled. However, there are counter examples, Kafka uses the term event, wikipedia page on the design pattern uses both

• The Observer pattern, which handles events immediately and often serially, on the other hand is more associated with the word event. For example the wikipedia page tends to prefer the term event to message. It only introduces the term message when describing how a message bus that can be used to buffer events which is effectively the first use case again where bevy uses the term message.

For me, the terms On and event are reminiscent to callbacks in JS/TS web frameworks and general observer pattern keywords. The term message is more reminiscent to AWS's queue services like SQS or Kinesis or other pub sub frameworks I'm familiar with.

Though, as I mentioned above, the term event is not universal, this seems like a change that came out of much discussion and I think we're probably stuck with it now either way.