dc43 0.18.0.0

Data contracts For Free using ODCS (Bitol)

dc43 — Data Contracts For Free!

Overview

Conceptual platform

dc43 is a governance-first toolkit that separates the concepts of data contract management from their implementations. At its core it provides:

• Contract lifecycle management primitives to draft, review, approve, and retire ODCS contracts. Note: dc43 currently targets ODCS 3.0.2; a compatibility table will follow as the spec evolves.
• Extensible interfaces for contract storage, drafting, and data quality orchestration that keep governance decisions close to the data contract owner.
• Runtime helpers to apply approved specifications in compute platforms while feeding observations back to governance workflows.

Provided integrations

On top of the conceptual platform, dc43 ships opinionated integrations that you can adopt or replace:

• Spark & DLT pipelines via dc43_integrations.spark.io with schema/metric helpers from dc43_service_backends.data_quality.backend for auto-casting and contract-aware IO.
• Storage backends such as filesystem (DBFS/UC volumes), Delta tables, and Collibra through CollibraContractStore.
• Open Data Product backends (dc43_service_backends.data_products.backend) that let product owners register ports and bind them to contracts via ODPS-compliant metadata stores.
• A pluggable data-quality client with a stub implementation that can be replaced by catalog-native tools.
• Scenario-first getting started guides (operations setup, local Spark flows, remote integrations, and the contracts app helper) live in docs/getting-started/.

See docs/implementations/data-quality-governance/collibra.md for end-to-end orchestration guidance when Collibra owns stewardship workflows. Component deep dives cover the contract store, contract drafter, data-quality governance interface, data-quality engine, and integration layer. Each component links to implementation catalogs under docs/implementations/ so you can pick technology-specific guides (Spark, Delta, Collibra, ...).

Component model

dc43 exposes a small set of well-defined components. Swap any of them without rewriting the rest of the stack:

Layer	Component	Responsibility
Governance	Contract manager/store interface	Retrieve, version, and persist contracts from catalog-backed or file-based sources.
Governance	Data product service interface	Manage ODPS data products, register input/output ports, and bind them to contract versions for runtime discovery.
Governance	Dataset↔contract link hooks	Propagate dataset/contract bindings to external catalogs (Unity Catalog, bespoke metadata APIs) after governance approves the linkage.
Governance	Data quality manager interface	Coordinate with an external DQ governance tool (e.g., Collibra, Unity Catalog) that records dataset↔contract alignment and approval state.
Authoring support	Contract drafter module	Generate ODCS drafts from observed data or schema drift events before handing them back to governance.
Runtime services	Data-quality metrics engine	Collect contract-driven metrics in execution engines and forward them to the governance tool for status evaluation.
Integration	Integration adapters	Bridge the contract, data product, drafter, and DQ components into execution engines such as Spark or Delta Live Tables (current adapters live under dc43_integrations.spark).

Guides for each component live under docs/:

• Contract store: component-contract-store.md
• Contract drafter: component-contract-drafter.md
• Data-quality governance interface: component-data-quality-governance.md
• Data-quality engine: component-data-quality-engine.md
• Integration layer: component-integration-layer.md; Spark & DLT adapter: implementations/integration/spark-dlt.md
• Write violation strategies: component-write-violation-strategies.md

Architecture

flowchart LR
    classDef external fill:#fef3c7,stroke:#b45309,stroke-width:1px;
    classDef dc43lib fill:#dbeafe,stroke:#1d4ed8,stroke-width:1px;
    classDef dc43svc fill:#ede9fe,stroke:#5b21b6,stroke-width:1px;
    classDef infra fill:#f3f4f6,stroke:#374151,stroke-dasharray:5 3;
    classDef ecosystem fill:#f1f5f9,stroke:#0f172a,stroke-width:1px;

    subgraph Producers & Runtimes
        direction TB
        Authoring["Authoring Tools\nNotebooks · CI Pipelines"]
        Pipelines["Business Pipelines"]
    end

    subgraph dc43 Integrations & Clients
        direction TB
        Integration["Integration Adapters\nSpark · DLT · HTTP"]
        Clients["Service Clients\ncontracts · governance · data products"]
    end

    subgraph dc43 Service Backends
        direction TB
        ContractSvc["Contract Service Backend\ninterface + stores"]
        Drafting["Drafting Service\nschema diff · proposals"]
        Governance["Governance Orchestrator\nlinking · approvals"]
        DataProductBackend["Data Product Backend\nODPS registry · ports"]
        QualityEngine["Data Quality Engine\nmetrics evaluation"]
        LinkHooks["Dataset↔Contract Hooks\nUnity Catalog · APIs"]
    end

    subgraph Stewardship Platforms
        direction TB
        StewardUI["Steward Console\nCollibra workflow · custom UI"]
        QualityTool["Data Quality Governance Tool\nCollibra · Unity Catalog"]
    end

    subgraph Storage & Catalog Backends
        direction TB
        ContractStores["Contract Stores\nFilesystem · Delta"]
        MetadataTargets["Metadata Catalogs\nUnity Catalog · APIs"]
    end

    Authoring --> Integration
    Pipelines --> Integration

    Integration <--> Clients

    Clients <--> ContractSvc
    Clients <--> Governance
    Clients <--> DataProductBackend

    Governance --> Drafting
    Drafting --> ContractSvc

    Governance --> QualityEngine
    QualityEngine --> Governance

    Governance --> LinkHooks
    LinkHooks --> MetadataTargets

    Governance <--> StewardUI
    Governance <--> QualityTool

    ContractSvc --> ContractStores
    DataProductBackend --> MetadataTargets

    class Authoring,Pipelines external;
    class Integration,Clients dc43lib;
    class ContractSvc,Drafting,Governance,DataProductBackend,QualityEngine,LinkHooks dc43svc;
    class ContractStores,MetadataTargets infra;
    class StewardUI,QualityTool ecosystem;

This architecture separates the libraries that ship with dc43 from the external systems they orchestrate:

• Producers & runtimes only call into dc43 through the integration adapters. Notebooks, CI pipelines, and Spark jobs import helpers such as dc43_integrations.spark.io which assemble schema metrics and forward requests to the services through typed clients.
• dc43 integrations & clients include the runtime adapters plus the request/response protocols defined under dc43_service_clients. These clients declare how to fetch contracts, submit governance assessments, and register ODPS ports without exposing storage details.
• dc43 service backends live in dc43_service_backends. They combine contract stores, the drafting module, the governance orchestrator, ODPS product registries, and the data-quality engine that materialises expectations from ODCS documents.
• Stewardship platforms (Collibra, Unity Catalog UIs, custom consoles) sit outside this repository. The governance backend offers hook points so approval workflows can run there while still receiving compatibility assessments and draft details via governance.backend.local and the hook interfaces in governance.hooks.
• Storage & catalog backends highlight the concrete infrastructure that backs each service: filesystem, SQL, or Delta-backed contract stores and metadata targets updated by link hooks such as governance.unity_catalog.

Node & edge glossary

• Integration adapters – runtime entry points (Spark, HTTP) that call every service through the typed clients, gather schema metrics, and assemble observation payloads for governance reviews. See spark/io.py and spark/data_quality.py.
• Service clients – thin protocols implemented by backends or HTTP gateways that expose contract, governance, and data-product actions to adapters without binding them to storage choices. Interfaces live under contracts/client, governance/client, and data_products/client.
• Contract service backend – resolves, versions, and stores ODCS documents using pluggable stores such as the filesystem adapter in contracts.backend.
• Drafting service – materialises schema diffs and draft ODCS payloads based on validation results so stewards can review suggested changes. Implementation details live in contracts/backend/drafting.py.
• Governance orchestrator – evaluates observation payloads, records compatibility results, triggers draft generation, and invokes dataset-link hooks during approvals via governance/backend/local.py and governance/hooks.py.
• Data product backend – persists ODPS product definitions and port bindings in repositories such as Delta tables or Collibra exports. See data_products/backend.
• Data quality engine – projects contract expectations into executable rules and reuses stored metrics when possible to cut redundant checks through data_quality/backend/engine.py.
• Dataset↔contract link hooks – extension points (for example the Unity Catalog linker) that propagate approvals to metadata catalogs after governance records a new binding. Implementations live under governance/unity_catalog.py.
• Storage and catalog backends – infrastructure that underpins the services: filesystem/Git paths, Delta tables, Unity Catalog, or bespoke APIs configured through the backend modules inside contracts/backend/stores and the Unity Catalog integration referenced above.

Variations—such as Collibra-governed contracts or bespoke storage backends—slot into the same model by substituting implementations of the interfaces described above.

Install

dc43 now ships as a family of distributions so you can install only the layers you need:

Distribution	Imports	Responsibility	Depends on
dc43-service-clients	dc43_service_clients.*	Typed service clients, request/response models, and governance helpers that front-end applications can embed.	open-data-contract-standard
dc43-service-backends	dc43_service_backends.*	Reference backend implementations (filesystem/SQL stores, local drafting, in-memory governance service) that orchestrate the client layer.	dc43-service-clients
dc43-integrations	dc43_integrations.*	Runtime adapters such as the Spark helpers that call into client APIs without requiring backend dependencies.	dc43-service-clients
dc43	dc43.*	Aggregating package that wires the CLI/demo and depends on the three modules above.	all of the above

Pip installs

• Service contracts only: pip install dc43-service-clients
• Backend reference services: pip install dc43-service-backends
• Backend services with SQL storage: pip install "dc43-service-backends[sql]"
• HTTP service backends: pip install "dc43-service-backends[http]" (see deploy/http-backend/README.md for a containerised deployment recipe)
• Spark integrations: pip install "dc43-integrations[spark]"
• Full stack: pip install dc43
• Spark extras for the meta package: pip install "dc43[spark]"
• Demo app: pip install "dc43[demo]"

When developing locally (Databricks Repos, workspace files, or any source checkout) the editable install automatically pulls in the sibling packages:

pip install -e .

Chain extras as needed—for example to prepare the test environment run:

pip install -e ".[test]"

Each distribution can now be installed independently. For example, lightweight clients can use pip install dc43-service-clients and then from dc43_service_clients.data_quality import ValidationResult without pulling in the backend or Spark helpers at runtime.

Quickstart

1. Define a contract (ODCS typed model)

from open_data_contract_standard.model import (
    OpenDataContractStandard, SchemaObject, SchemaProperty, Description
)

contract = OpenDataContractStandard(
    version="0.1.0",
    kind="DataContract",
    apiVersion="3.0.2",
    id="sales.orders",
    name="Orders",
    description=Description(usage="Orders facts"),
    schema_=[
        SchemaObject(
            name="orders",
            properties=[
                SchemaProperty(name="order_id", physicalType="bigint", required=True, unique=True),
                SchemaProperty(name="customer_id", physicalType="bigint", required=True),
                SchemaProperty(name="order_ts", physicalType="timestamp", required=True),
                SchemaProperty(name="amount", physicalType="double", required=True),
                SchemaProperty(
                    name="currency", physicalType="string", required=True,
                    logicalTypeOptions={"enum": ["EUR", "USD"]}
                ),
            ],
        )
    ],
)

2. Validate and write with Spark

from dc43_service_backends.contracts.backend.stores import FSContractStore
from dc43_service_clients.contracts import LocalContractServiceClient
from dc43_integrations.spark.io import (
    write_with_contract,
    ContractVersionLocator,
)

store = FSContractStore(base_path="/mnt/contracts")
contract_service = LocalContractServiceClient(store)

write_with_contract(
    df=orders_df,
    contract_id="sales.orders",
    contract_service=contract_service,
    expected_contract_version=">=0.1.0",
    dataset_locator=ContractVersionLocator(dataset_version="latest"),
    mode="append",
    enforce=True,
    auto_cast=True,
)

3. DLT usage (inside a pipeline notebook)

import dlt
from dc43_service_clients.contracts import LocalContractServiceClient
from dc43_service_clients.data_quality import LocalDataQualityServiceClient
from dc43_integrations.spark.dlt import contract_table

contract_service = LocalContractServiceClient(store)
data_quality_service = LocalDataQualityServiceClient()


@contract_table(
    dlt,
    name="orders",
    contract_id="sales.orders",
    contract_service=contract_service,
    data_quality_service=data_quality_service,
    expected_contract_version=">=0.1.0",
)
def orders():
    df = spark.read.stream.table("bronze.sales_orders_raw")
    return df.select("order_id", "customer_id", "order_ts", "amount", "currency")

Need to experiment outside Databricks? Install databricks-dlt for the official notebook-compatible shims (the local mode only flips a flag). If the package is not available the helpers now fall back to an in-repo stub so the demo pipeline and tests continue to run, but installing the real package is recommended for parity. Wrap your pipeline definitions in LocalDLTHarness (see packages/dc43-integrations/examples/dlt_contract_pipeline.py) to execute the same annotations on a local Spark session and inspect the recorded expectation verdicts.

4. Store and resolve contracts

from dc43_service_backends.contracts.backend.stores import FSContractStore

store = FSContractStore(base_path="/mnt/contracts")
store.put(contract)
latest = store.latest("sales.orders")

5. DQ/DO orchestration on read

from dc43_integrations.spark.io import read_with_contract, ContractVersionLocator
from dc43_service_clients.contracts import LocalContractServiceClient
from dc43_service_clients.governance import build_local_governance_service

governance = build_local_governance_service(store)
contract_service = LocalContractServiceClient(store)
df, status = read_with_contract(
    spark,
    contract_id="sales.orders",
    contract_service=contract_service,
    expected_contract_version="==0.1.0",
    governance_service=governance,
    dataset_locator=ContractVersionLocator(dataset_version="latest"),
    return_status=True,
)
print(status.status, status.reason)

6. Quality status check on write

from dc43_integrations.spark.io import write_with_contract, ContractVersionLocator
from dc43_service_clients.contracts import LocalContractServiceClient

contract_service = LocalContractServiceClient(store)
vr, status = write_with_contract(
    df=orders_df,
    contract_id="sales.orders",
    contract_service=contract_service,
    expected_contract_version=">=0.1.0",
    dataset_locator=ContractVersionLocator(dataset_version="latest"),
    mode="append",
    enforce=False,                 # continue writing
    governance_service=governance,
    return_status=True,
)
if status and status.status == "block":
    raise ValueError(f"DQ blocked write: {status.details}")

Demo application

A Vue-powered FastAPI application packaged as dc43-demo-app (module dc43_demo_app) offers a visual way to explore contracts, datasets and data quality results. Install the optional dependencies and launch the app with:

pip install ".[demo]"
dc43-demo

Visit http://localhost:8000 to:

• Browse contracts and their versions with draft/active status.
• Inspect dataset versions, their linked contract, validation status and detailed DQ metrics derived from contract rules.
• Highlight datasets using draft contracts and trigger validation to promote them.

An additional Reveal.js presentation is available at http://localhost:8000/static/presentation.html to walk through the contract lifecycle and automation steps.

The application also exposes an example Spark pipeline in dc43_demo_app.pipeline used when registering new dataset versions. The preconfigured scenarios are documented in docs/demo-pipeline-scenarios.md including the new split strategy example that writes orders_enriched::valid and orders_enriched::reject alongside the main dataset.

The demo now drives its contract, governance, and data-quality operations through the same HTTP clients that production pipelines use. When the UI starts it spins up an in-process instance of the service backend HTTP application, so Spark runs exercise the remote code paths without requiring an external deployment.

Running the service backend over HTTP

Pipelines that rely on the remote clients can reach a standalone backend via the dc43_service_backends.webapp module. Set the contract directory and (if needed) a bearer token before launching uvicorn:

export DC43_CONTRACT_STORE=/path/to/contracts
export DC43_BACKEND_TOKEN="super-secret"  # optional
uvicorn dc43_service_backends.webapp:app --host 0.0.0.0 --port 8001

Contracts stored under $DC43_CONTRACT_STORE are served over the API while the stub data-quality and governance backends keep draft information on disk. See docs/implementations/service-backends/http-server.md for Docker packaging notes and deployment options.

Spark Flow (Mermaid)

flowchart LR
    subgraph Read
      U[User code / Notebook] --> RWC{read_with_contract}
      RWC --> SR["spark.read.format(...).load"]
      RWC --> EV["ensure_version(contract)"]
      EV --> OBS[collect_observations]
      OBS --> DQS["dq_service.evaluate"]
      DQS -->|ok| AC["apply_contract (cast/order)"]
      DQS -->|errors & enforce| E1[Raise]
      AC --> DF[DataFrame ready]
      RWC --> DQ{dq_client?}
      DQ -->|yes| GS["get_status(dataset@version, contract@version)"]
      GS -->|unknown/stale| CM[compute_metrics]
      CM --> SM[submit_metrics -> status]
      GS -->|up-to-date| SM
      SM -->|block & enforce| E2[Raise]
      SM -->|ok/warn| DF
    end

    DF --> T[Transformations / joins / aggregations]

    subgraph Write
      T --> WWC{write_with_contract}
      WWC --> OBS2[collect_observations]
      OBS2 --> DQS2["dq_service.evaluate"]
      DQS2 -->|ok| AC2[apply_contract]
      DQS2 -->|errors & enforce| E3[Raise]
      DQS2 -->|errors & !enforce| AC2
      AC2 --> SW["spark.write.(format, options).mode.save"]
      SW --> DELTA[Delta table / UC]
      DELTA --> DQ2{dq_client?}
      DQ2 -->|yes| EVAL["evaluate_dataset"]
      EVAL -->|status block & enforce| E4[Raise]
      EVAL -->|status ok/warn| DELTA
    end

    classDef err fill:#ffe5e5,stroke:#ff4d4f,color:#000
    class E1,E2,E3,E4 err

Notes

• The library uses the official ODCS package and enforces $schema version 3.0.2 by default (configurable via DC43_ODCS_REQUIRED).
• Validation runs inside the Spark DQ engine: presence, types, nullability and common constraints (enum, regex, min/max, unique best-effort). The resulting ValidationResult bundles metrics and a schema snapshot so governance adapters can update compatibility matrices.
• DLT helpers translate constraints into expect expressions when feasible.
• DQ orchestration: the IO wrapper checks schema vs contract and consults the DQ client. If dataset version is newer than DQ’s known version, it computes the required metrics and submits them, then enforces the resulting status if requested.

Local Dev

• Install dependencies locally (match your Databricks runtime where possible):

pip install open-data-contract-standard==3.0.2 pyspark

• dc43 enforces apiVersion via DC43_ODCS_REQUIRED (default 3.0.2).

Tests

• Install the shared test extras and run the suites that matter for the area you are touching. The top-level pytest configuration automatically adds each package's src directory to sys.path, so cloning the repo and running pytest works even before the editable installs finish building.

# Option A: run everything with one helper (installs extras unless --skip-install is passed)
./scripts/test_all.sh

# Option B: manage installs yourself and invoke pytest directly
pip install -e ".[test]"
pytest -q tests packages/dc43-service-clients/tests \
  packages/dc43-service-backends/tests packages/dc43-integrations/tests

Publishing

• Push a tag v* on a commit in main.
• The workflow .github/workflows/release.yml runs tests, builds the package, waits for manual approval via environment release, publishes to PyPI, and creates a GitHub release with autogenerated notes.
• Set PYPI_TOKEN secret and configure the release environment with required reviewers.

License

Apache 2