Clarify that log attributes are NOT standard attributes

[pellared]

What are you trying to achieve?

Currently, logs attributes are different from standard (resource, trace, metrics) attributes.
However, there may be a desire to make unify them as some languages already use standard attributes for defining log attributes.

I want to have clarification that log attributes are distinct from standard attributes before stabilizing OTel Go Bridge API.

My proposal is to explicitly call out that log attributes are different.

Additional context.

Follow-up to: #2888 (comment)

Prior PRs:

• Update Attributes field type in Logs Data Model #3816
• Support maps and heterogeneous arrays as attribute values #2888

There seem to be no consensus whether the standard attributes should be expanded to support complex types.

I don't believe we'll reach a consensus on limiting log attributes to only accommodate types defined by standard attributes. This would be also a breaking specification change.

I also want to point out that the Bridge API does anyway require the ability to support complex types for log record body. Therefore, the log attributes can be defined using the types used for modelling body.

Moreover, OTLP already supports complex types for attributes so there is no technical need to limit the log attribute values.

Related issues:

• Clarify handling empty (null) values in Logs Data Model #3835
• Clarify scalar value types in Logs Data Model #3836

[trask]

I don't believe we'll reach a consensus on limiting log attributes to only accommodate types defined by common attributes. This would be also a breaking specification change.

Deprecation would be an option

[pellared]

SIG meeting notes:

It may sense to have log attributes to be modeled differently than standard attributes as the purpose of Logs Bridge API is to support what existing structured logging libraries offer. Some applications use complex values for attributes and end-users would like to keep them.

The Event API may (to be discussed) restrict the attributes and accept only standard attributes.

The semantic conventions should use only standard (non-complex) attributes.