20-EFT.WP.Metrology.TimeBase v1.0 | Chapter 14 — Quality Metrics, SLOs & Dashboards

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Chapter 14 — Quality Metrics, SLOs & Dashboards

One-line objective: With a unified SLI/SLO vocabulary, quantify the accuracy, stability, and availability of the time-base service, and close the loop from paneling to error budgets in an auditable way.

I. Scope & Targets

1. Covered
   • Publication quality of internal tau_mono and external ts, health of synchronization chains, harmonization of arrival time, and jitter control.
   • Statistical windows & aggregation: rolling/sliced windows Delta_t, quantiles pXX, error budgets and burn-down (burn rate).
   • Visualization & audit: TS.sli.* dashboard fields, thresholds tol_*, alerts, and rollback integration.
2. Inputs
   • Base observations: offset, skew, J, offset_1pps, delta_form, adev(tau), mdev(tau), hdev(tau).
   • Event streams: source_switch, holdover, leap_event, smear_active, failover, drift_alarm.
   • Policy: tol_offset, tol_skew, tol_J, tol_Tarr, target SLOs, and alerting strategies.
3. Outputs
   • Quality reports: report.sli, report.slo, burn_rate.*, q_score.
   • Dashboards: overview / accuracy / stability / source health / events & rollback / compliance.
   • Manifest mapping: manifest.time.sli.* and manifest.time.slo.*.

II. Terms & Variables

• Accuracy-related: offset (s), skew (ppm), J (s), offset_1pps (s), p50/p95/p99(x).
• Stability-related: adev(tau), mdev(tau), hdev(tau) with tau ∈ {1, 10, 100, ...}(s).
• Arrival consistency: dual-form T_arr and delta_form; threshold tol_Tarr (s).
• Availability & budgets: good(t) ∈ {0,1}, SLO_target ∈ (0,1], error budget EB, burn_rate.
• Panel fields: TS.sli.offset.p99, TS.sli.skew.p99, TS.sli.J.p99, TS.sli.adev.tau_*, TS.sli.delta_form.max.
• Units & dimensions: unit(x), dim(x), check_dim(expr) — all in SI and [T] coherent.

III. Axioms P514- **

• P514-1 (Window consistency): Compute all SLIs on tau_mono, publish on ts; attach uncertainties for offset/skew/J.
• P514-2 (Invariant gauges): Quantile definitions and ADEV/MDEV/HDEV estimators are fixed; no in-window estimator switching.
• P514-3 (Additive error budgets): Error budgets are chainable across windows; burn rate scales with window multiplicity for multi-horizon alerts.
• P514-4 (Dual-form mandatory): Whenever T_arr appears, record both forms and delta_form.
• P514-5 (Monotonic & traceable): non_decreasing(ts) and signed traceability (Ch. 13); dashboards reference signed, persisted metrics only.
• P514-6 (Unit conservation): Run check_dim(expr) prior to publication; normalize units before cross-field arithmetic.

IV. Minimal Equations S514- **

• S514-1 (Quantile definition)
  p_q(x) = inf{ z : ( ∑_{j=1..N} 1{ x_j ≤ z } ) / N ≥ q }，q ∈ (0,1)。
• S514-2 (Availability & SLO evaluation)
  Define pass predicate
  g_i = 1{ |offset_i| ≤ tol_offset ∧ |skew_i| ≤ tol_skew ∧ J_i ≤ tol_J ∧ delta_form_i ≤ tol_Tarr }；
  window SLI: SLI = ( ∑ w_i * g_i ) / ( ∑ w_i )；window SLO pass: pass = 1{ SLI ≥ SLO_target }。
• S514-3 (Error budget & burn rate)
  EB = max( 0 , SLO_target - SLI )；
  burn_rate_W = ( bad_time_W / ( (1 - SLO_target) * W ) ) with window length W。
  Multi-scale burn: burn_rate = max( burn_rate_W1 , burn_rate_W2 )。
• S514-4 (RMS jitter & Allan family)
  J_rms = sqrt( (1/N) * ∑ (offset_i - mean(offset))^2 )；
  adev(tau), mdev(tau), hdev(tau) follow Chapter 7’s definitions (phase differencing & overlap estimators)。
• S514-5 (Dual-form arrival difference)
  delta_form = | ( 1 / c_ref ) * ( ∫ n_eff d ell ) - ( ∫ ( n_eff / c_ref ) d ell ) | with delta_form ≤ tol_Tarr。
  The integration path gamma(ell) and measure d ell must be explicit.

V. Measurement & Publication Flow M50-14 (Collect → Aggregate → Evaluate → Visualize → Persist)

• Collect
  From sync/observation stacks, gather offset/skew/J/1pps/adev/* and events; simultaneously pull both T_arr forms.
• Aggregate
  On window Delta_t, compute p50/p95/p99, J_rms, adev(tau); produce TS.sli.*.
• Evaluate
  Apply S514-2 and S514-3 to compute SLI, EB, burn_rate; emit report.slo.
• Visualize
  Render dashboards: overview / accuracy / stability / source health / events / compliance; stamp release_tag and TraceID.
• Persist
  Write manifest.time.sli.* and manifest.time.slo.*; sign and chain per Chapter 13.

VI. Contracts & Assertions C50-14*

• C50-141 (Quantile gates): |offset|_p99 ≤ tol_offset ∧ |skew|_p99 ≤ tol_skew ∧ J_p99 ≤ tol_J.
• C50-142 (ADEV gates): adev(tau_k) ≤ adev_max(tau_k) for target grid tau_k.
• C50-143 (Dual-form difference): max(delta_form) ≤ tol_Tarr.
• C50-144 (Availability SLO): SLI ≥ SLO_target; otherwise degrade or roll back.
• C50-145 (Burn-rate alerts): burn_rate ≥ br_hi → high-priority alert; burn_rate ≥ br_mid → pre-alert.
• C50-146 (Panel integrity): required_fields ⊆ TS.sli.* ∧ check_dim(all) = pass ∧ signature_valid = true.
• C50-147 (Monotonicity & gaps): violations( non_decreasing(ts) ) = 0 ∧ missing_rate(TS.sli.*) ≤ m_thr.

VII. Implementation Bindings I50-14*

• collect_sli(ds, sensors, window) -> sli_raw
• aggregate_sli(sli_raw, window, quantiles, taus) -> TS.sli.*
• compute_allan(ds, taus, mode) -> {adev, mdev, hdev}
• evaluate_slo(TS.sli.*, targets) -> {SLI, EB, burn_rate, pass}
• render_time_panels(TS.sli.*, report, layout) -> dashboard
• emit_sli_manifest(TS.sli.*, report) -> manifest.time.sli
• slo_alerts(report, policy) -> actions
• Invariants: unique(TraceID); mean(weights)=1 (if weighted); unit/dimension checks pass; delta_form exists and has been evaluated.

VIII. Cross-References

• Sources for servo & sync panels: Chapter 5.
• Robust offset/skew/jitter estimation: Chapter 6.
• Allan-family definitions & estimators: Chapter 7.
• Arrival-time metrology & path harmonization: Chapter 9.
• Compliance, contracts & signed releases: Chapter 13.
• Streaming ops & backpressure indicators: Chapter 11.

IX. Panel Design & Operational Notes

1. Panel sections
   • Overview: offset_p50/p95/p99, J_p99, SLI, burn_rate, holdover_duration_s.
   • Accuracy: time series and quantile bands for offset and offset_1pps.
   • Stability: multi-tau adev/mdev/hdev curves with target bands.
   • Source health: pdop, cn0, source_switch_count, smear_active_flag.
   • Events & rollback: leap_event, failover, drift_alarm, rollback_to(tag) records.
   • Compliance: contract_fail_rate, signature_valid, audit_gap_seconds.
2. Ops rules
   • Multi-window burn: monitor a short window W1 (5 min) and a long window W2 (1 h); trigger on the maximum burn rate.
   • Rollback loop: if C50-144 fails or burn_rate ≥ br_hi, enact gray degradation and rollback_to(last_good).
   • Change control: any threshold or gauge change requires a new release_tag and re-signing of the manifest.

Summary