What is the purpose of SchemaURL?

[maxifom]

I can see SchemaURL in the code everywhere, but it doesn't get exported by prometheus exporter, is it intended? And what the SchemaURL is used for?

[MrAlias]

The schema URL defines the version of semantic conventions used in resource. Each version of semantic conventions will export a unique schema URL that defines the form of the semantic conventions and the transforms to others.

opentelemetry-go/semconv/v1.4.0/schema.go

Lines 17 to 19 in cdf67dd

	// SchemaURL is the schema URL that matches the version of the semantic conventions
	// that this package defines. Semconv packages starting from v1.4.0 must declare
	// non-empty schema URL in the form https://opentelemetry.io/schemas/<version>

For more information on the schema URL take a look at the OTEP they were introduced with: https://github.com/open-telemetry/oteps/blob/09e285ec83d9f67759d99433f9ef1b32cd0551ca/text/0152-telemetry-schemas.md#schema-url

I imagine when the Prometheus exporter becomes stable it will include this information, but currently it is not expected to export this data.

Hope that helps.