See #4178 for the context.

Internal kind is defined as

Presumably it means that span cannot have remote parents and remote children.

Based on discissions referenced in #4178, #110, #526:

• instrumentations don't know if underlying layer is instrumented. Underlying layer may be instrumented, not enabled, or conditionally suppressed (still propagating current context)
• there are multiple nested layers of physical operations (e.g. HTTP -> DNS) and lower layers don't usually support context propagation
• there are protocols that don't support context propagation (yet)
• there are multiple layers that each support context propagation (e.g. messaging + CloudEvents over HTTP could carry 3 different contexts at the same time)

I.e. there is no reliably way to know whether something will have remote children (or any descendants). It depends on application, enabled instrumentations, potentially interchangeable protocols.

INTERNAL vs SERVER is also controversial. Imagine a cron-job (e.g. FaaS time trigger) - it never has a parent, should it be Internal?

The existing status-quo:

• the boundary between INTERNAL and CLIENT or SERVER in the spec is unclear.
• semantic conventions that describe logical operations (DB, messaging, LLM) document the kind