EventTypeDefinitions, CRDs and Event Types themselves

[Matthias Wessendorf]

Hi group!

The lack of meta information about EventTypes in general, on the cluster, is a well understood problem. To address this we have the feature track for "Event Type Definitions":
https://docs.google.com/document/d/1vwEWtAm28g_QY9j0b63h8sRpGhvyB1K5ViNr8X3vIiM/edit#heading=h.jh94w0llm99a

The current thinking is that any event type can be part of a category, or event-type-definition, as discussed in the feature track.

Relationship between them?

However, how do we really define the relationship between EventType and their optional EventTypeDefinition?

We have built-in Source CRDs, like below:

```
k get crds -l 'duck.knative.dev/source'
...
apiserversources.sources.knative.dev   2023-03-15T12:49:47Z
pingsources.sources.knative.dev        2023-03-15T12:49:47Z
...
```

Could we use those reversed (and in singular) as the EvenTypeDefinition "name/id", resulting in like

```
dev.knative.sources.apiserversource
dev.knative.sources.pingsource
```

If so... we could use our CRD/Duck source reconciler and create these EvenTypeDefinition for our own sources and set a reference/annotation on _each_ event type, pointing to its group.


For custom integrations e.g. some "batch / legacy" deployment, do we recommend to create EvenTypeDefinition for their event types?

--

Matthias Wessendorf