# Glossary Plain definitions of the terms used across the Mnemontron site and product, each with how Mnemontron applies it. For the product overview, start at the [home page](/). ## Provenance-aware knowledge infrastructure A system for storing and retrieving knowledge that keeps the origin of every fact attached to it. Mnemontron is built this way: each answer carries citations to the preserved source, the version and the exact span it came from. ## Evidence chain The three linked records behind every Mnemontron answer: the preserved source, the attributed claim extracted from it, and a signed receipt that connects the answer to the source's content hash and version. Following the chain from receipt to source is how a reader checks an answer. ## Content addressing Identifying a piece of data by a hash of its bytes instead of by a name or location. Mnemontron identifies evidence by its BLAKE2b hash, so any change to the bytes produces a new identity and a new version. ## Custody status A label that says who holds the original copy of a source. Mnemontron uses four states: locally preserved, contractually preserved by a custodian, reference only, and unavailable or unverified. ## Attributed claim A statement extracted from evidence and linked to the exact spans that support or oppose it, with an epistemic status. Claims, originals, extracts and embeddings are stored as distinct records. ## Agent verification and human verification Two separate records of who checked a claim. A claim checked by an agent is marked `agent_verified`; a claim checked by a person is marked human-verified with who verified it. Mnemontron never merges the two. ## Abstention Declining to answer when the available evidence does not support an answer. Mnemontron measures abstention as its own result: how often unanswerable questions are correctly declined. ## Answer-support check A test of whether the cited evidence actually supports an answer, run separately from the test of whether the evidence is relevant to the question. ## Hybrid retrieval Combining several retrieval methods and merging their results. Mnemontron combines BM25 lexical search, dense embeddings and reranking, and every result carries citations to evidence hashes and versions. ## Signed receipt A digitally signed record that links an answer to its evidence. Mnemontron receipts are Ed25519-signed JSON Web Signatures listing each citation's evidence id, content hash, version and URL, with a nonce and an expiry. See [how to verify a receipt](/verify-a-receipt). ## Replay detection Recognizing a receipt that is presented more than once. Each Mnemontron receipt carries a unique nonce; the verification API records it on first use and flags any later presentation as a replay. ## Rights revocation Withdrawing permission to use a source. When a source is revoked in Mnemontron, it is hidden from retrieval, purged from search and vector indexes and caches, and blocked from being ingested again. ## Historical retrieval Answering a question as of a past date. Mnemontron keeps versions of evidence and claims so that a query can be run against what was known at that time, and versions can be compared. ## Staleness and missing-material flags Markers on results whose sources are out of date or no longer available. Mnemontron shows these flags next to results without silently changing the ranking. ## Envelope encryption Encrypting data with a data key and then encrypting that data key with a master key. Mnemontron seals each tenant's evidence with its own AES-256-GCM data key, wrapped by a master key. ## Row-level tenant isolation Restricting every database query to the rows of one tenant. Mnemontron uses Postgres row-level security, on top of membership checks, so one tenant's queries cannot read another tenant's records. ## Hash-chained audit log An audit log in which each entry includes a hash of the previous entry, so deleting or editing an entry breaks the chain. Mnemontron also signs the chain head periodically and writes it to write-once storage. ## Capacity projection An estimate of how a system would behave at a scale that has not been tested. Mnemontron's 100+ exabyte figure is a capacity projection built from measured runs and architectural assumptions; it is not a test that was run. Measured runs are on the [benchmarks page](/benchmarks).