Glossary

Attribute. An entity in :db.part/db that declares a name, a value type, a cardinality, and optional properties. See schema management.

AEVT. The covering index sorted by attribute, entity, value, transaction. It holds all current datoms.

AVET. The covering index sorted by attribute, value, entity, transaction. It holds the datoms of indexed and unique attributes only.

Acknowledgement code. A stable, kebab-case name for a schema change whose meaning changes, passed back with --ack.

Basis. The transaction number, written t, that a database value covers.

BLAKE3. The hash function that addresses blobs.

Blob store. The immutable, content-addressed half of the storage service.

Cardinality. Whether an attribute holds one value or many per entity.

Chunk. A content-defined run of a sorted key stream. A published leaf is exactly one chunk.

Class key. The key that seals values on the attributes of one protection class. A process resolves it through its own keyring.

Covering index. An index that holds whole datoms, so an answer needs no second lookup.

Database root. The record in the root store that names a database: its basis, its index roots, its log root, and its write lease.

Database value. An immutable snapshot of a database at one basis.

Datom. One fact: entity, attribute, value, transaction, and assert or retract.

EAVT. The covering index sorted by entity, attribute, value, transaction. It holds all current datoms.

Entity id. A 64-bit number: a 22-bit partition and a 42-bit sequence.

Epoch (storage key). One generation of the per-database data key. New writes seal under the newest open epoch.

Execution class. How much work a schema change needs: additive, validate-reindex, rewrite, or destructive.

Fence. The mechanism that stops a deposed writer. Every root write is a compare-and-set on the record that holds the lease.

Fork. A new database that duplicates an existing one at a basis, and then diverges. See forking a database.

Fuel. A budget on the datoms a query touches, or on the work a database function does.

Group commit. Committing concurrent transactions as one batch under one durability boundary, while each keeps its own t and its own acknowledgement.

Ident. A keyword that names an entity, above all an attribute.

Index basis. The transaction number that the published index trees cover.

Index lag. The difference between the basis and the index basis.

KEK. Key-encryption key. It wraps the per-database data key. Corium never stores it.

Key policy. Whether a serving process hydrates a caller with the class keys that policy names (strict) or with its whole keyring (server-wide).

Lease. The right to write one database. It lives in the database root and is renewed by compare-and-set.

Lease version. The generation of a lease. It names the log file, or the log key prefix, that its holder appends to.

Lookup reference. A [attribute value] pair on a unique attribute, usable anywhere an entity id is expected.

Partition. The high bits of an entity id. Entities of one partition sort together in EAVT.

Peer. A library, or a process, that holds a database value and queries it locally.

Peer server. A peer hosted as a standalone process for thin clients.

Plan digest. The hash of a schema plan. --apply refuses a digest that no longer describes the change.

Principal. The identity of a request, produced by an identity provider.

Protection class. A named key identity and sealing policy. An attribute that names one has its values sealed by the writing peer. See attribute protection.

ReBAC. Relationship-based access control, the authorization model that --authz-db enables.

Retirement. The schema change that refuses new assertions on an attribute while keeping its ident, its metadata, and its history readable.

Root store. The small, mutable, strongly consistent half of the storage service. It is updated only by compare-and-set.

Schema generation. A per-database counter that advances once for each committed transaction containing a schema change.

Segment. An immutable, content-addressed node of an index tree.

Standby. A transactor that polls a lease held elsewhere and takes over when it lapses.

Storage plugin. A dynamic library that registers a storage backend at run time. See storage backends.

Tempid. A transaction-local placeholder for an entity id, resolved at commit. A collision on a :db.unique/identity attribute becomes an upsert.

Transaction report. The record that a commit broadcasts to peers: the basis before, the basis after, the datoms, and the tempid map.

Transactor. The single writer for a database.

Unmanaged attribute. An installed attribute that the desired schema file does not name. corium schema update leaves it alone unless --prune is given.

Upsert. Unifying a tempid with an existing entity through a :db.unique/identity attribute.

VAET. The covering index sorted by value, attribute, entity, transaction. It holds reference-typed datoms.

View. A policy object that hides attributes from a principal, names the class keys the principal can use, or both.

t. The sequence part of a transaction id, and the name of a basis.

:db/txInstant. The commit time of a transaction, asserted as a datom on the transaction entity.