Glossary

agent — The ReAct loop running inside oos or oosd that turns natural language into tool calls (schema search, GraphQL queries, DSL saves) and assembles the result into a response.

backfill — The process oosai runs on startup to embed any domain, view, global prompt or event records that are not yet represented in the vector store.

domain — A named description of one data entity. Written in the domain DSL (.domain). Describes the database table, fields, types, permissions, relations, meta sources and AI hints. The source of truth for everything OOS generates: GraphQL schema, LLM chunks, UI.

domain chunk — The plain-text representation of a domain, produced by renderLLMChunk in packages/oos-dsls-ts. Embedded as a vector and used for semantic retrieval by the agent.

event — One row in an event source table. Events are inserted via oos.cmd.event.insert, embedded by oosai, and searchable by semantic similarity.

event mapping — A named configuration (oos.event_mappings) that connects a source table to the event system and lists which event type grammars it accepts.

event stream — A named context within a mapping, typically a case file, session or thread. Identified by a stream ID (e.g. fall-2024-0042).

event type grammar — A DSL source in oos.event_type_grammar that describes one class of event: required/optional fields, context tags and examples. Edited in oosd’s Event Types panel.

global prompt — A row in oos.global_prompt. Every global prompt is injected verbatim into the LLM system prompt on every turn. Used for standing instructions: deletion policy, filter conventions, response style, permission reminders.

knowledge sandwich — The system prompt design used in oos. Global standing instructions and the domain index form the stable outer layers; on-demand schema chunks retrieved by oos_schema_search fill the middle as the agent works.

meta source — A lookup table backing a dropdown field. Declared in the domain with the meta keyword. Loaded by oosgql to populate dropdown options.

NATS — The message bus used for all inter-service communication. OOS uses NATS Request-Reply exclusively. All clients only need a NATS URL; they do not know the addresses of individual services.

oosai — The embedding and command hub. Handles all NATS subjects, maintains the vector store, drives the event embedding pipeline, and proxies GraphQL calls to oosgql.

oosd — The designer desktop app. Used by developers to write domain and view DSL files, manage event type grammars, and install the demo dataset.

oosgql — The GraphQL gateway. Builds a live GraphQL schema from domain definitions and executes queries and mutations against PostgreSQL.

oos — The chat desktop app. End users query and edit data in natural language through a local ReAct agent.

pgvector — A PostgreSQL extension for storing and querying embedding vectors. Used by oosai for domain chunks, global prompt chunks and event embeddings.

ReAct — Reasoning + Acting. The agent loop pattern: ask LLM, if it requests tools run them, append results, repeat. Used in both oos and oosd.

renderLLMChunk — The function in packages/oos-dsls-ts that converts a DomainDef into a structured plain-text block for embedding. Output is deterministic and versioned.

view — A named description of how a domain is presented. Written in the view DSL (.view). Describes toolbar actions, table columns, form sections and widget bindings.