Glossary
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.
Attachment
Supporting documentation linked to one or more records — a URL, uploaded file, or IPFS link.
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.
CGS (Certified Group Service)
An AT Protocol service that sits between clients and a group's backing PDS and adds role-based access control, record-authorship tracking, and an audit log. Lets multiple identities co-manage a single ATProto repository with member/admin/owner roles. See Certified Group Service (CGS).
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.
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.
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.
ePDS (extended PDS)
A standard AT Protocol PDS with Certified's email/OTP login extension on top, so users can sign in with just an email and a one-time code. From an app's point of view, OAuth against an ePDS still finishes with a normal AT Protocol authorization code. See ePDS (extended PDS) and the list of Certified-operated ePDS instances on Certified PDSs.
Evaluation
A third-party assessment of a hypercert. Created on the evaluator's own account, not the original author's.
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.
Hyperindex
A reference indexer that indexes hypercert records across the network and exposes them via a GraphQL API. Other indexers exist — see Hyperindex.
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.
Measurement
A quantitative observation attached to a hypercert (e.g., "12 pages written", "50 tons CO₂ reduced").
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 a Certified-operated PDS, Bluesky's, or self-host one. Records are portable between PDS instances.
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.
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.