---
title: "Glossary"
description: "Notarium terms: space, project, notarium-id, note class, principal, PAT, revision log, RRF, and more."
---

# Glossary

Short definitions of the key Notarium terms. Each term links to the page where it's explained in full.

## Storage and identity

**file-first** — the principle that the source of truth is the Markdown files themselves, on disk. The search index, the link graph, and everything derived can be rebuilt from the files; you can grab the folder and walk away at any time. More in [File-first](/docs/concepts/file-first/).

**space** — an isolated knowledge base with its own index, graph, search, tree, revision log, and member roster. Every user has a non-deletable personal space (on the agent-facing pages it's called the **personal domain**). More in [Spaces and projects](/docs/concepts/spaces-and-projects/).

**project** — a lightweight, optional entity: a marked folder with a stable identity inside a space (the marker is a dot-file at the folder root). An agent addresses it by the handle `space/slug`. More in [Spaces and projects](/docs/concepts/spaces-and-projects/).

**`notarium-id`** — a stable 12-character note identifier in the frontmatter. It survives moving and renaming the file, so links and history never break. More in [Version history](/docs/concepts/versioning/).

**note class** — a set of visibility and indexing policies derived from where the note is stored (not a free-form field): `user-doc` (user note, visible everywhere), `agent-memory` (agent memory, indexed and reachable via `recall` but hidden from user-facing surfaces), plus the internal `attachment`, `derived`, and `profile`. More in [Note types](/docs/concepts/note-types/).

## Access and agents

**principal** — a generalized access subject: a person or an AI agent. One grant mechanism for all of them. More in [Access model](/docs/concepts/access-model/).

**roles** — membership in a space: `reader` (reads everything), `writer` (edits notes), `owner` (manages membership). More in [Access model](/docs/concepts/access-model/).

**PAT (Personal Access Token)** — a personal access token for agents, sent in the `Authorization: Bearer …` header. It carries a scope (`read`/`write`), optional space scoping, and an expiry. The secret is shown exactly once. More in [Connecting an agent](/docs/agents/connect/).

**MCP gateway** — the built-in `POST /mcp` endpoint through which an AI agent reads and writes the knowledge base using intent-oriented tools (rather than generic CRUD operations). An agent's edits are versioned, bounded by access, and signed with provenance. More in [Agents and MCP](/docs/agents/).

**intent tool** — an MCP gateway tool that expresses an intent ("find," "create a note") rather than a low-level CRUD operation on storage. More in [Intent tools](/docs/agents/intent-tools/).

## Search

**hybrid search** — a fusion of three channels: lexical (full-text FTS/BM25, always on), semantic (vectors, enabled by a flag), and an optional graph boost. The results are combined by the RRF algorithm. More in [Search](/docs/concepts/search/).

**RRF (Reciprocal Rank Fusion)** — an algorithm that weights and fuses ranked lists (lexical + semantic + graph) into a single result set without a shared score scale. More in [Search](/docs/concepts/search/).

**degradation** — a capability falling back to a simpler variant when its dependencies aren't there: if the vector stack is off or unavailable, search keeps working over full text (FTS) — with no error, and the same result. More in [Search setup](/docs/self-hosting/search-setup/).

## Versions and provenance

**revision log** — the version history of notes in the metadata database (not git). A revision is a full snapshot of state; identical states are deduplicated by content. The log is keyed by `notarium-id`, so history survives move/rename. More in [Version history](/docs/concepts/versioning/).

**provenance** — the attribution of each revision: who made the edit and how — a specific person, a specific AI agent, or an external file editor. More in [Version history](/docs/concepts/versioning/).

## Deployment

**self-host** — Notarium's deployment model: a single self-contained container (Node/Fastify, engine in-process, no external services). Privacy comes from owning the server and the files, not from end-to-end encryption. More in [Self-host](/docs/self-hosting/).

## See also

- [Environment variables](/docs/reference/environment-variables/) — the full configuration table.
- [Keyboard shortcuts reference](/docs/reference/keyboard-shortcuts/) — layouts and presets.
- [Concepts](/docs/concepts/) — how Notarium is built.