# Concepts

Key terms used throughout Orxaq.

**World DAG** — The central data structure: a directed acyclic graph where nodes are entities (variables) and edges are causal mechanisms. Every analysis in Orxaq operates on or through the World DAG.

**Entity** — A node in the World DAG. Has an ID, name, causal role, and variable type. Examples: `unemployment_rate` (exogenous), `credit_score` (mediator), `default_flag` (outcome).

**Causal Edge** — A directed edge in the World DAG representing a causal mechanism from source to target. Carries metadata: mechanism description, confidence score, soliton score, provenance.

**Causal Role** — Classification of an entity's position in the causal graph. `EXOGENOUS` (no parents — externally determined), `MEDIATOR` (has parents and children), `OUTCOME` (terminal node).

**Soliton Score** — A stability metric (0.0 to 1.0) measuring how resilient a causal edge or decision is to perturbation. Named after soliton waves that maintain their shape through collisions. Higher scores indicate more robust causal relationships.

**D-Separation** — A graphical criterion for conditional independence. If two variables are d-separated given a conditioning set, they are independent in any distribution faithful to the DAG. Used for validation and falsification.

**Operator** — The human user who configures and oversees Orxaq. Makes architectural decisions, reviews PRs, approves sprint transitions.

**Conductor** — The orchestration agent that decomposes high-level goals into tasks, delegates to workers, and enforces compliance gates.

**Worker** — An execution agent that performs a single task (run tests, generate code, analyze data). Workers operate under Conductor supervision.

**Skin** — A user interface layer (Ring 5). Gamma Observatory is the first skin: a read-only dashboard for monitoring. Future skins include Beta (interactive analysis) and Alpha (full editing).

**Quality Gate** — A predicate that data must satisfy before proceeding through the pipeline. Gates check completeness, bounds, types, uniqueness, and freshness.

**ADR** — Architecture Decision Record. A structured document capturing the context, options, decision, and consequences of a significant design choice. All ADRs live in `docs/adr/`.
