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OrionBelt® Semantic Layer and Sidecar¶

An open-source Semantic Sidecar for agentic AI, analytics, data quality, and governance systems.

Inject governed semantics into systems that never had them.

OrionBelt Semantic Layer (OBSL) is a thin runtime that sits next to existing platforms — AI agents, BI tools, data-quality pipelines, regulatory and KPI reporting — and injects governed business semantics without forcing those systems to absorb a new semantic infrastructure.

Define dimensions, measures, metrics, business rules, and semantic context in declarative YAML models. OBSL compiles and executes them as optimized, dialect-specific SQL across BigQuery, ClickHouse, Databricks, Dremio, DuckDB / MotherDuck, MySQL, PostgreSQL, and Snowflake — surfaced over REST, MCP, Arrow Flight SQL, and the PostgreSQL wire protocol.

Query using business concepts — not raw tables and SQL. The same semantic model powers AI agents, analytics workflows, data-quality checks, regulatory and business KPIs, and reporting use cases. Analytics as Code — and beyond. The full loop from declarative YAML through executable SQL, DQ rules, KPIs, and semantic context to query results is programmable, reviewable, and reproducible — no BI tool in the middle.

What is a Semantic Sidecar?¶

The sidecar pattern comes from container platforms: a small, focused process runs alongside a main application and adds capability the main process doesn't have, without changing it.

OBSL applies the same pattern to semantics:

It's a runtime, not a rewrite. Existing BI tools, AI agents, governance systems, and DQ pipelines keep talking to their databases — OBSL attaches a governed semantic interface alongside them.
It's multi-surface by design. The same model is reachable over REST (for agents and apps), MCP (for LLM clients), Arrow Flight SQL + PostgreSQL wire (for BI tools), and direct DB-API drivers (for Python). One model, many channels.
It's opinionated about correctness, not deployment. Dialect-aware SQL generation, fan-trap-safe joins, and dimensional metrics are non-negotiable; where to run OBSL — embedded in your app, alongside a warehouse, behind a proxy, in a single container — is your call.
It's open by default. BSL 1.1 today, converts to Apache 2.0 in 2030. No SaaS lock-in is required to use the full v2.6 surface.

The OrionBelt trio¶

OBSL ships three named pillars. You author models in OBML, query them in OBSQL, and run it all on OBSL.

Short form	Full name	What it is	Reference
OBSL	OrionBelt Semantic Layer	The system itself — compiler, planner, runtime, REST / Flight / Postgres-wire surfaces	this site
OBML	OrionBelt Modeling Language	Declarative YAML format for defining models	OBML Model Format
OBSQL	OrionBelt Semantic QL	SQL surface BI tools and humans actually write — bare-label or `MEASURE()` syntax, aggregation-match validation, `WITH ROLLUP` / `WITH CUBE`, no escape hatch to raw SQL	OBSQL reference

OBSQL flows over Apache Arrow Flight SQL (v2.4+) and PostgreSQL wire (v2.5+). Same language, two transports — pick whichever your BI tool prefers.

Why OrionBelt?¶

One model, many consumers — Author dimensions / measures / metrics / business rules once in YAML; agentic AI, BI tools, DQ pipelines, regulatory KPIs, and reporting all read from the same governed surface
Analytics as Code — and beyond — Version-controlled YAML compiles to dialect-specific SQL, executable DQ rules, KPI definitions, and semantic context. No BI tool in the middle: the full loop from declarative model to query results is programmable, reviewable, and reproducible
One model, many dialects — BigQuery, ClickHouse, Databricks, Dremio, DuckDB / MotherDuck, MySQL, PostgreSQL, and Snowflake — no runtime lock-in to any single warehouse
One model, many transports — REST + MCP (for agents), Arrow Flight SQL + PostgreSQL wire (for BI tools), DB-API drivers (for Python). Choose the surface; the semantics are the same
Cross-schema & cross-database — Model data objects across multiple schemas and databases; dimensions, measures, and metrics can span schema boundaries in a single query
Safe by construction — AST-based SQL generation prevents injection and ensures syntactic correctness
Precise error reporting — Validation errors include line and column numbers from your YAML source
Static model filters — Bake mandatory WHERE conditions into the model (by status, region, date range, etc.) — applied to every query automatically, with auto-join extension and ISO 8601 date/timestamp support
Automatic join resolution — Declare relationships between data objects; OrionBelt finds optimal join paths using graph algorithms
Multi-fact support — Composite Fact Layer (CFL) planning handles queries spanning multiple fact tables with UNION ALL and CTE-based aggregation
Artefacts Composability Resolution (ACR) — Given the query so far, the composables endpoint returns which dimensions, measures, and metrics can still be added and compile (including CFL candidates), powering guided query building for people and AI agents
Machine-readable semantics — Every loaded model is exported as an OBSL-Core 0.1 RDF graph and queryable via a read-only SPARQL endpoint, so AI agents and knowledge-graph tools can reason over your model
Session management — TTL-scoped sessions isolate model state per client, enabling iterative development workflows

Key Features¶

Feature	Description
8 SQL Dialects	BigQuery, ClickHouse, Databricks, Dremio, DuckDB/MotherDuck, MySQL, Postgres, Snowflake
OrionBelt ML (OBML)	YAML-based data objects, dimensions, measures, metrics, joins
Cross-Schema Queries	Dimensions, measures, and metrics can span multiple databases and schemas in a single query
Static Model Filters	Mandatory WHERE conditions on any column, auto-join, ISO 8601 dates, deduplicated with query-time filters
Star Schema & CFL	Automatic fact selection and join path resolution
Session Management	TTL-scoped per-client sessions for the REST API
REST API	FastAPI endpoints for session-based model management, validation, compilation, execution, and OSI conversion
Gradio UI	Interactive web interface for model editing, query testing, SQL compilation, ER diagrams, and OSI import/export
Custom Extensions	Vendor-specific metadata at all model levels (model, data object, column, dimension, measure, metric)
DB-API 2.0 Drivers	PEP 249 drivers for all 8 databases with transparent OBML compilation
Arrow Flight SQL	Embedded gRPC server for DBeaver, Tableau, Power BI — single container, two ports
PostgreSQL Wire	Native Postgres-protocol surface (v2.5.0+) — Tableau, DBeaver, Superset, Power BI, `psql`, and Dremio as a federated Postgres source connect via their built-in Postgres ODBC/JDBC driver; no new connector to install
OBSL Graph & SPARQL	Every loaded model is exported as an OBSL-Core 0.1 RDF graph (Turtle) with a read-only SPARQL (SELECT/ASK) endpoint
Plugin Architecture	Extensible dialect system with capability flags
Source Tracking	Error messages with YAML line/column positions

Try the demo¶

Hosted Gradio UI: orionbelt.ralforion.com — pre-loaded example model, compile across dialects, see SQL instantly. (Swagger · ReDoc)

The hosted demo runs on Cloud Run (HTTPS-only by design), so the PostgreSQL wire and Arrow Flight SQL transports can't be exposed publicly there. Spin the same demo up locally in one docker run — same image, same baked-in orionbelt_1_commerce DuckDB dataset, plus all three transports:

docker run --rm -d --name orionbelt-demo \
  -p 8080:8080 -p 5432:5432 -p 8815:8815 \
  -e PGWIRE_ENABLED=true \
  -e FLIGHT_ENABLED=true \
  ralforion/orionbelt-semantic-layer-api:latest

# REST + Gradio UI:
#   http://localhost:8080/ui
# pgwire (any psql / DBeaver / Tableau / Power BI / Superset / Metabase):
psql "host=localhost port=5432 user=obsl dbname=orionbelt_1_commerce sslmode=disable" \
  -c 'SELECT "Client Name", "Total Sales" LIMIT 5'
# Flight SQL smoke test:
uv run python examples/obsql.py 'SELECT "Client Name", "Total Sales" LIMIT 5'

docker stop orionbelt-demo

The container ships with PGWIRE_AUTH_MODE=trust (default) — fine for localhost, not safe to expose to the public internet until SCRAM / password auth lands on the pgwire surface.

Quick Example¶

Define a semantic model in YAML:

# yaml-language-server: $schema=schema/obml-schema.json
version: 1.0

dataObjects:
  Customers:
    code: CUSTOMERS
    database: WAREHOUSE
    schema: PUBLIC
    columns:
      Customer ID:
        code: CUSTOMER_ID
        abstractType: string
      Country:
        code: COUNTRY
        abstractType: string

  Orders:
    code: ORDERS
    database: WAREHOUSE
    schema: PUBLIC
    columns:
      Customer ID:
        code: CUSTOMER_ID
        abstractType: string
      Price:
        code: PRICE
        abstractType: float
        numClass: non-additive
      Quantity:
        code: QUANTITY
        abstractType: int
        numClass: additive
    joins:
      - joinType: many-to-one
        joinTo: Customers
        columnsFrom:
          - Customer ID
        columnsTo:
          - Customer ID

dimensions:
  Country:
    dataObject: Customers
    column: Country
    resultType: string

measures:
  Revenue:
    resultType: float
    aggregation: sum
    expression: "{[Orders].[Price]} * {[Orders].[Quantity]}"

Compile a query to SQL:

result = pipeline.compile(query, model, "postgres")

SELECT
  "Customers"."COUNTRY" AS "Country",
  SUM("Orders"."PRICE" * "Orders"."QUANTITY") AS "Revenue"
FROM WAREHOUSE.PUBLIC.ORDERS AS "Orders"
LEFT JOIN WAREHOUSE.PUBLIC.CUSTOMERS AS "Customers"
  ON "Orders"."CUSTOMER_ID" = "Customers"."CUSTOMER_ID"
GROUP BY "Customers"."COUNTRY"

Getting Started¶

Ready to dive in? Start with Installation and then follow the Quick Start tutorial.

Commercial Offerings¶

OrionBelt Semantic Layer is open by default — the OSS distribution has full parity on the shipped v2.6 surface and is production-grade for self-hosted use. For teams that want production support, a managed runtime, or embedded analytics terms, RALFORION offers:

Embedded analytics license — relicensing terms for shipping OBSL inside a commercial product
Commercial cloud offering — managed OrionBelt runtime with SLAs
Enterprise features — capabilities tailored for enterprise deployments
Consulting + support — implementation, modeling, and production support

Contact RALFORION d.o.o. for details.