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Reliability Analytics & Self-Serve Tooling1 / 3

1 min lesson

The semantic / metric layer

Tell someone how to act on this idea: "A semantic layer defines each metric once."

Step 1 of 3

The semantic / metric layerdefine once, agree everywhere

Without a metric layer, every team writes its own SQL for "success rate," and three dashboards disagree by lunch. A semantic layer defines each metric once - the exact filter, the denominator, the sessionization - so every dashboard, alert and query resolves to the same definition. It kills the "whose number is right" debate that quietly drains trust.

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Full explanation

A metric defined once in the semantic layer

A metric defined once in the semantic layer - every consumer inherits this
metric: agent_success_rate
  description: Share of admitted agent runs that reach a success outcome
  source: agent_interactions
  entity: run_id                 # sessionized: one row per logical attempt
  filter: surface = 'agent' AND is_bot = false
  numerator:   count(run_id) where outcome = 'success'
  denominator: count(run_id)     # admitted attempts, includes censored = failure
  dimensions: [model, region, client_version, surface]
  owner: reliability-ds