From Wikitech

This page will document EventLogging's EventCapsule, a wrapper that stores meta information about EventLogging events. The EventCapsule is stored in the EventLogging source code in eventlogging/ Before February 2018, it was stored with other schemas on meta wiki. As part of, it was moved to source code, as the codebase's operation is highly dependent on the EventCapsule structure. Changes to EventCapsule need to be coordinated with source code deployments. will be maintained for documentation purposes, but the canonical EventCapsule schema lives at eventlogging/