What this is

Principia is a source-graded survey of organizational measurement — predominantly the people side of organizations — output in two shapes: a book manuscript and a queryable database. It is the continuously-updated, citation-verified, Bayesian-prior-bearing registry of organizational science: theories, constructs, measures, instruments, items, citations, and effect sizes, synthesized into the prior distributions researchers and practitioners plug into their own analyses.

The same construct gets measured five ways across five studies; effect tables are scattered through textbooks; good instruments get reinvented badly. Principia is the single graded, sourced, queryable place to look — and the canonical measurement vocabulary the platform subscribes to.

Public surface: peopleanalyst.com/research/principia.

Who it's for

• Builders / researchers / operators querying graded constructs, instruments, and effect sizes.
• Sibling apps (toolbox, CanonicAI, Vela) consuming the registry through @measurement/core types.
• Analysts pulling Bayesian priors and scoring confidence (θ̂) for decisions.

Interface shape (hybrid)

Principia exposes both a measurement-engine REST/MCP API and a typed registry data contract (@measurement/core). Both are documented here (APIs + Data Contracts).

Documentation tree

Overview ........................ this page
Concepts ........................ concepts.md          (construct · instrument · grade · prior · the registry · Credible/Living/Useful)
Getting Started ................. getting-started.md   (query the registry · score confidence · methods advisor)
Architecture .................... architecture.md      (registry · measurement engines · @measurement/core · ingestion from CanonicAI)
APIs & Data Contracts ........... apis.md              (/api/v1/* engines + the @measurement/core typed registry)
Trust & Grading ................. trust-and-grading.md (source grading · citation verification · novelty · priors provenance)
Interface reference (generated) . reference-apis.generated.md · reference-mcp.generated.md

Source of truth

• Vocabulary: @measurement/core (Construct · Instrument · Item · Measure · Model · EffectSize · Publication · StudyQualityGrade).
• Registry rows: construct-family surveys under docs/research/reports/; resolved spine (CanonicalVariable, CanonicalSurveyItem).
• Capabilities: docs/capability-manifest.json. Spec: docs/specification/SPEC.md.

See also

Concepts · Getting Started · Architecture