The goal of the specifications has changed as of 20181017 - mid RC0/RC1 of Casablanca.
To not impact development teams with spec changes - we will publish the logging spec at the end of the previous release - in the case of Dublin - at the end of Casablanca.
This will allow teams to implement the spec and library changes and not impact back end indexing/reporting systems with "in the past" schema changes.
The current spec is dublin