Attributes:

Key	Stability	Value Type	Description	Example Values
opentracing.ref_type	OpenTracing compatibility requirements are deprecated in OpenTelemetry Specification	string	Parent-child Reference type [1]	child_of; follows_from

[1] opentracing.ref_type: The causal relationship between a child Span and a parent Span.

opentracing.ref_type has the following list of well-known values. If one of them applies, then the respective value MUST be used; otherwise, a custom value MAY be used.

Value	Description	Stability
child_of	The parent Span depends on the child Span in some capacity
follows_from	The parent Span doesn't depend in any way on the result of the child Span