Glossary

Hypercert

A structured digital record of a contribution: who did what, when, where, and with what evidence. The core primitive of the protocol. Technically, a hypercert is an activity claim record with linked contributions, attachments, measurements, and evaluations.

Activity claim

The central record in the hypercerts data model. Describes the work that was done, when, and in what scope.

AT-URI

The permanent, globally unique identifier for a record. Looks like at://did:plc:abc123/org.hypercerts.claim.activity/3k7. You'll see these in every API response — they're how records reference each other.

DID (Decentralized Identifier)

A permanent identifier for a user or organization. Looks like did:plc:abc123xyz. You get one when you create an account on certified.app or Bluesky. Your DID never changes, even if you switch servers or handles. Every record you create carries your DID as the author.

Strong reference

A reference to another record that includes both the AT-URI and a content hash (CID). Used when one record points to another (e.g., an evaluation referencing an activity claim). The CID makes the reference tamper-evident — if the target record changes, the hash won't match.

Evaluation

A third-party assessment of a hypercert. Created on the evaluator's own account, not the original author's.

Attachment

Supporting documentation linked to one or more records — a URL, uploaded file, or IPFS link.

Measurement

A quantitative observation attached to a hypercert (e.g., "12 pages written", "50 tons CO₂ reduced").

Contribution

Who contributed to a hypercert. Can be as simple as a DID string, or a richer record with display name, image, role, and timeframe.

Collection

A named group of hypercerts and/or other collections, with an optional weight per item. Each collection has a type (e.g., "favorites", "project") so the same hypercert can appear in different collections for different purposes.

Lexicon

A versioned schema that defines the structure of a record type. Lexicons enable interoperability — any app that knows the schema can read the record. See Introduction to Lexicons.

Work scope

The "what" dimension of a hypercert — what work is being claimed. Can be a simple free-text string or a structured CEL expression for machine-evaluable scopes. See Work Scopes.

Hyperindex

A reference indexer that indexes hypercert records across the network and exposes them via a GraphQL API. Other indexers exist — see Indexers & Discovery.

PDS (Personal Data Server)

The server where your records are stored. You interact with it through the ATProto API — you don't need to manage it directly. You can use the Hypercerts Foundation's PDS, Bluesky's, or self-host one. Records are portable between PDS instances.

Certified

The identity provider for the Hypercerts ecosystem. We built Certified to give the ecosystem a unified entry point — one account that works across all Hypercerts applications. When you sign up at certified.app, you get a DID, a PDS, and an embedded wallet. See Account & Identity Setup.