Glossary
Terms are listed alphabetically. Each entry links to the page that explains it in full.
Acknowledgement
A record in which an account accepts or rejects a relationship that someone else stated, such as being named as a contributor or having an activity included in a collection. See Acknowledgement.
Activity claim
The record that describes a piece of work: what is being done or was done, by whom, when, and where. Also called a hypercert. Evidence, evaluations, and funding receipts point to it. See Activity Claims.
AT Protocol
The open network technology that Hypercerts is built on, also used by Bluesky. It gives every account an identity and a repository for its records, and lets any application read them. See Why AT Protocol?.
AT-URI
The address of a record on the network, such as at://did:plc:abc123/org.hypercerts.claim.activity/3k7. It names the account, the record type, and the record's key. The record at that address can change; a CID identifies one exact version.
Attachment
A record that connects material such as a document, photo, dataset, or link to the records it concerns. See Evidence and Measurements.
Backfill
Catching up on records that were published before you started listening. Jetstream keeps an archive so a new consumer can load past records before following the live stream.
Badge
A way for a network or certifier to recognize an account or a record. A badge definition describes the recognition, a badge award gives it to a recipient, and a badge response lets the recipient accept or reject it. See Trust and Recognition.
Blob
A file stored alongside an account's records, such as an image or a PDF. Records refer to blobs; the PDS stores them.
CBOR
Concise Binary Object Representation, the compact binary format AT Protocol uses to store and transmit records. Most applications work with JSON instead, through Jetstream or an API.
Certified
The identity service operated by the Hypercerts Foundation: accounts, sign-in, group accounts, and the app.certified record types for profiles, organizations, locations, and badges. Applications don't have to use Certified to use Hypercerts.
Certified account
An AT Protocol account hosted by the Hypercerts Foundation. It gives a person or organization one identity and one place for their records, and lets them sign in to Hypercerts applications with an email address. See certified.app.
certified.app
The web app where people create a Certified account and manage it: profile, connected applications, groups, and endorsements. See certified.app.
Certified Group Service (CGS)
The service that lets several people manage one account together, with member, admin, and owner roles. Used for organizations and projects. See Certified Group Service.
Certified PDS
A PDS hosted by the Hypercerts Foundation for Certified accounts. See Certified PDSs.
CID
Content identifier: a hash of a record's contents. Changing the record changes its CID, so a CID identifies one exact version. See Records That Change Over Time.
Collection
Two meanings. In Hypercerts, a collection is a record that groups activities, features, or other collections; a project is a collection of type project. See Projects and Collections. In AT Protocol, a collection is also the set of an account's records of one type, named by an NSID.
Contribution
Information about who took part in an activity and what they did. It can be written inline on the activity or kept in reusable contributor and contribution records. See Contribution.
Cursor
A bookmark in a stream of events. A consumer saves the position of the last event it processed and sends it when reconnecting, so it resumes where it left off.
DID (decentralized identifier)
The permanent identifier of an AT Protocol account, such as did:plc:abc123xyz. It stays the same when the account changes its handle or moves to another server.
Endorsement
A public statement by one account that it vouches for another account or its work. Endorsements are published records, so applications can show them and use them as trust signals.
Entryway
The service that signs users in to their Certified accounts and connects them to the PDS that stores their records. It is under development and will take over sign-in from ePDS. See Entryway.
ePDS (extended PDS)
A standard PDS with an added sign-in layer: users log in with an email address and a one-time code. The Certified PDSs run ePDS today. The Entryway will replace this role.
Evaluation
A record containing an assessment of work, published by the evaluator from their own account and linked to what it assesses. See Evaluations.
Feature
A record describing something the work concerns that is not a person or organization, such as a land zone or a participant cohort. See Feature.
Feed
An ordered list of recent activity, such as new projects or evaluations from accounts a user follows. The Feed Service provides ready-made feeds.
Firehose
The continuous stream of every record change that a relay publishes. Events are in CBOR and include the signed data needed to verify them.
Funding receipt
A record describing a funding payment: who paid whom, how much, and for which work. It describes a payment; it does not move money or prove that payment arrived. See Funding and Learning.
Handle
An account's readable name, such as alice.certified.one. A handle can change; the account's DID does not.
Hypercert
Another name for an activity claim: a record describing a piece of work, which evidence, evaluations, and funding records can attach to.
Hypercerts API
The XRPC service applications use to query Hypercerts and Certified records across the network, served at api.hypercerts.dev. See API and indexer for how it works and the endpoint explorer.
Hypercerts Protocol
The Hypercerts and Certified Lexicons together with the conventions for using them. It defines how work, evidence, evaluations, and funding are described so that different applications understand the same records.
Indexer
A service that collects records from many accounts and organizes them into a searchable view. The Hypercerts API provides this kind of view for Hypercerts and Certified records. See Hypercerts API.
Jetstream
A service that turns the firehose into a filtered stream of record changes in plain JSON. The Hypercerts Jetstream keeps only the record collections it is configured for, such as Hypercerts and Certified records. See Relay and Jetstream.
Label
A short tag that a labeler attaches to a record or an account, such as likely-test or high-quality.
Labeler
An account that publishes labels about records or accounts. Applications choose which labelers to trust. See Labelers.
Lexicon
A schema that defines one type of record or API method: its fields, their types, and their constraints. See Introduction to Lexicons.
Location
A record describing a place or area, which activities, collections, and features can refer to. See Location.
Measurement
A record of a quantitative observation: what was measured, the value, the unit, and optionally the method. See Evidence and Measurements.
NSID
Namespaced identifier: the name of a Lexicon, such as org.hypercerts.claim.activity. Records carry it in their $type field.
OAuth
The standard way a user grants an application limited access to their account without sharing a password. AT Protocol applications sign users in with OAuth.
Organization
A record with details about an organization, such as its type and founding date, kept alongside its profile. See Organization.
PDS (Personal Data Server)
The server that hosts an account's repository and serves its records to applications. Accounts can move between PDSs without changing identity. See Certified PDSs.
Permission set
A named group of permissions that an application requests during sign-in. org.hypercerts.authWrite and app.certified.authWrite allow an application to create, update, and delete Hypercerts and Certified records.
Profile
A record with an account's display name, description, avatar, and banner. See Profile.
Project
A group of related activities followed as a whole. In Hypercerts, a project is a collection with its type set to project. See Projects and Collections.
Record
A small structured document published by an account, such as an activity claim or an evaluation. Every record has a type, defined by a Lexicon, and an address, its AT-URI.
Record key
The last part of a record's address, which identifies it among the account's records of the same type.
Relay
A service that connects to many PDSs and merges the changes they publish into one stream, the firehose. See Relay and Jetstream.
Repository
The collection of all records an account has published. It lives on the account's PDS and is signed, so anyone can check that a record came from that account.
Rights
A record stating the rights or licensing terms attached to an activity. See Rights.
SDK
The Hypercerts library for creating, reading, and validating records from an application. It is under development. See SDK.
Service auth token
A short-lived token that a user's PDS issues so a service can confirm who is calling it. Used when calling the Certified Group Service and the Feed Service.
Strong reference
A link to another record that includes both its AT-URI and its CID, so it points to one exact version. An evaluation uses a strong reference to say which version of an activity it assessed.
Trust signal
Information that helps someone decide whether to rely on a project or its work: project updates, endorsements, evaluations, certifications, and funding records, each attributed to whoever provided it. See Trust and Recognition.
Vocabulary tag
A reusable term for classifying Hypercerts records. Today collections and features refer to it, so directories can group projects by subject. See Vocabulary Tag.
Work scope
The description of what an activity covers. It can be plain text or a structured expression that software can compare. See Describing and Classifying Work.
XRPC
The way AT Protocol services expose their APIs: HTTP requests to named methods, each defined by a Lexicon. Queries read data and procedures change it.