Sampling

I. Formal Definition

The deliberate retention of a fraction of telemetry events according to a documented rule, with the explicit acceptance that the unretained events are not available for retrospective analysis. Sampling is a mature engineering response to scale, not a workaround. The federation requires that sampling rules be deterministic where possible, that head-based and tail-based strategies be distinguished in disclosure, and that the effective sampling rate be reported alongside any aggregated metric derived from sampled traces under UFMS-001:2.4.

II. Etymology

Statistical sampling theory dates to the early twentieth century; the application to distributed-tracing emerged with the Google Dapper paper of 2010.

III. Federation Usage

Federation members operating tail-based sampling must publish the gating criteria. Members operating head-based sampling at sub-percent rates must disclose the implications for trace completeness under MEV-Annex:3.2.

IV. Related Terms

• traces
• cardinality
• retention
• otel

V. Authoritative Citations

• UFMS-001:2.4UFMS Article II - Sampling Discipline
• MEV-Annex:3.2MEV Annex III - Sampling Disclosure

VI. Citation in BibTeX

@misc{ifo4_glossary_sampling,
  title        = {{Sampling}},
  author       = {{IFO4 Federation Editorial Board}},
  howpublished = {{IFO4 Federation Glossary, slug \texttt{sampling}}},
  year         = {2026},
  url          = {https://ifo4.org/glossary/sampling},
  note         = {Category: Observability; key: Sampling}
}

VII. Challenge This Definition

Federation members and accredited practitioners may challenge any entry under TGS-002:1.7. Filed challenges are routed to the editorial board, triaged into the revision register, and resolved in writing on the public docket. The slug remains stable through any revision.