Initial OSI <> dbt Semantic Layer converters by QMalcolm · Pull Request #116 · apache/ossie

QMalcolm · 2026-04-29T16:33:04Z

The initial implementation of the OSI <> dbt Semantic Layer converters. This is initially written in python as the simplest path forward required taking MetricFlow as a dependency, though that doesn't need to be the case longer term.

Introduces the shared Python type library for the OSI specification, establishing it as the canonical Python representation of the core spec. All future Python converters will depend on this package rather than defining their own OSI types. Key decisions: - Pydantic v2 native (no shim): OSI has no obligation to support dbt-core's Pydantic v1/v2 compatibility constraints - Python 3.11+ minimum: clean modern syntax, no __future__ annotations - uv + hatchling: consistent with the data tooling ecosystem - PyPI name `osi-python`, import namespace `osi` - `to_osi_yaml()` added alongside `to_osi_json()` since YAML is OSI's native serialization format - OSIRelationship.from_dataset aliased to `from` (YAML/JSON key) via Field(alias="from") with populate_by_name=True so Python callers can use the non-keyword name

Migrates the dbt↔OSI converters from metricflow/metricflow/converters/ into the OSI repository as the osi-dbt package. Source changes from metricflow: - converter_issues.py: direct copy; drop `from __future__ import annotations` - expression_utils.py: direct copy - filter_utils.py: direct copy - msi_to_osi.py: update imports from `metricflow.converters.models` → `osi`; replace all `LazyFormat(...)` calls with f-strings (no metricflow dep) - osi_to_msi.py: same import updates as msi_to_osi.py - cli.py: new file; file-driven CLI for both conversion directions using `parse_manifest_from_dbt_generated_manifest` from metricflow_semantics The `osi-dbt` package depends on `osi-python` (the shared OSI types added in the previous commit) and `metricflow` directly, since `metricflow-semantic-interfaces` is not separately published on PyPI. Build tooling: uv + hatchling, matching the pattern from osi-python.

Migrates tests from tests_metricflow_semantic_interfaces/osi/ into the OSI repository. Import changes from metricflow: - `metricflow.converters.models` → `osi` - `metricflow.converters.msi_to_osi` → `osi_dbt.msi_to_osi` - `metricflow.converters.osi_to_msi` → `osi_dbt.osi_to_msi` - `tests_metricflow_semantic_interfaces.osi.helpers` → `tests.helpers` Snapshot testing: replaced metricflow's `assert_object_snapshot_equal` + `SnapshotConfiguration` with syrupy's `snapshot` fixture. Snapshot assertions compare `result.to_osi_yaml()` (a stable string representation) rather than the raw Pydantic object. Syrupy was chosen over the metricflow helper because it has no dependency on the metricflow test infrastructure and stores snapshots as plain text files in the repository. `[tool.pytest.ini_options]` added to pyproject.toml to point pytest at the `tests/` directory.

Covers installation, CLI usage for both conversion directions, Python API usage, conversion loss notes (what gets dropped and why), and development setup.

Add Ontology & Semantic Interoperability as a top-level current effort with links to discussions apache#22, apache#101, apache#108, apache#68 and PRs apache#124, apache#125. Update existing sections with recently opened discussions, PRs, and converters: metric trees (apache#40), primary key semantics (apache#15, apache#119), reusable datasets (apache#103, apache#109), datatype/is_time reframe (PR apache#113), spatial dimension types (apache#114), default_aggregation (apache#115), positive direction (apache#41), physical metadata (apache#110), and new converter PRs for Salesforce (apache#118), dbt (apache#116), and Databricks (apache#120). Also adds CONTRIBUTING.md (apache#122) and working groups page (apache#123) to Developer Experience, and lists merged converters as existing artifacts. Made-with: Cursor

Add Ontology & Semantic Interoperability as a top-level current effort with links to discussions #22, #101, #108, #68 and PRs #124, #125. Update existing sections with recently opened discussions, PRs, and converters: metric trees (#40), primary key semantics (#15, #119), reusable datasets (#103, #109), datatype/is_time reframe (PR #113), spatial dimension types (#114), default_aggregation (#115), positive direction (#41), physical metadata (#110), and new converter PRs for Salesforce (#118), dbt (#116), and Databricks (#120). Also adds CONTRIBUTING.md (#122) and working groups page (#123) to Developer Experience, and lists merged converters as existing artifacts. Made-with: Cursor

khush-bhatia · 2026-05-27T18:29:57Z

+                issues.append(
+                    ConverterIssue(issue_type=ConverterIssueType.CUMULATIVE_SEMANTICS_LOSS, element_name=metric.name)
+                )
+            expr = self._resolve_metric_expression(metric, metric_index, expression_cache)
+            osi_metrics.append(
+                OSIMetric(
+                    name=metric.name,
+                    expression=self._make_expression(expr),
+                    description=metric.description,
+                )
+            )


For cumulative metrics, looks like continue is missing ?

So for cumulative metrics, we don't skip them, we just drop the extra information about them that we aren't able to represent yet. However we can still produce the basic representation, and then emit a warning about what information was dropped.

khush-bhatia

LGTM, thanks , just left one comment.

MAQL is present in the OSI schema's Dialect definition but was missing from the Python enum, making it impossible to represent GoodData expressions in the Python SDK.

GOODDATA appears in OSI examples but was missing from the enum, causing validation failures for any document that references GoodData extensions.

The OSI project as a whole has advanced to 0.2.0.dev0. Updates all version references across the spec, schema, examples, Python packages, and tests.

jbonofre

LGTM to overall. I left a couple of comments/questions, especially about is_time (to clarify).

jbonofre · 2026-06-02T14:09:33Z

+
+    model_config = ConfigDict(frozen=True)
+
+    is_time: bool


The spec describes is_time as optional, but here it's required.

I believe we should use Optional[bool] = None here.

WDYT?

Will make the change! Might be worth reviewing that in the spec later though 🤔 What does the third state give us if None is the same as False?

jbonofre · 2026-06-02T14:11:48Z

+                metrics=metrics,
+                project_configuration=PydanticProjectConfiguration(),
+            ),
+            issues=[],


Correct me if I'm wrong, but ConverterIssue is never thrown here? Should we?

Presently there are no converter issues going OSI to MSI, issues only exist going MSI to OSI currently. However, I wanted to use the same ConverterResult class to make future work where there are OSI -> MSI converter issues easier to handle without a breaking change. We could add a

if result.issues: for issue in result.issues: verb = "was dropped" if issue.issue_type in _DROPPED_ISSUE_TYPES else "was converted with loss" reason = _ISSUE_REASON[issue.issue_type] print(f"[WARNING] {issue.issue_type.value}: {issue.element_name} {verb} during conversion because {reason}", file=sys.stderr)

block to _cmd_osi_to_msi in converters/dbt/src/osi_dbt/cli.py, but that would be dead code at this time.

The spec marks is_time as optional, but the Pydantic model had it as a required bool. Aligning to Optional[bool] = None so documents that omit is_time validate correctly.

QMalcolm added 3 commits April 29, 2026 11:12

jbonofre self-requested a review April 29, 2026 16:36

Add README for osi-dbt converter

3a0080b

Covers installation, CLI usage for both conversion directions, Python API usage, conversion loss notes (what gets dropped and why), and development setup.

QMalcolm force-pushed the feat/dbt-converter-migration branch from b35fd90 to 3a0080b Compare April 29, 2026 17:17

Improve CLI warning messages with drop reason and verb

fdc13ce

khush-bhatia self-requested a review May 5, 2026 03:47

jklahr mentioned this pull request May 18, 2026

Add ontology section and update roadmap with latest discussions #126

Merged

khush-bhatia reviewed May 27, 2026

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khush-bhatia approved these changes May 27, 2026

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jbonofre approved these changes May 28, 2026

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Comment thread python/src/osi/models.py

Comment thread python/src/osi/models.py

QMalcolm and others added 4 commits June 1, 2026 12:29

Merge branch 'main' into feat/dbt-converter-migration

109edc8

Add MAQL to OSIDialect enum

45f64f5

MAQL is present in the OSI schema's Dialect definition but was missing from the Python enum, making it impossible to represent GoodData expressions in the Python SDK.

Add GOODDATA to OSIVendor enum

6539134

GOODDATA appears in OSI examples but was missing from the enum, causing validation failures for any document that references GoodData extensions.

Bump project version to 0.2.0.dev0

4afc54f

The OSI project as a whole has advanced to 0.2.0.dev0. Updates all version references across the spec, schema, examples, Python packages, and tests.

QMalcolm requested review from jbonofre and khush-bhatia June 2, 2026 01:28

jbonofre approved these changes Jun 2, 2026

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khush-bhatia approved these changes Jun 2, 2026

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Make OSIDimension.is_time optional per spec

75da5a6

The spec marks is_time as optional, but the Pydantic model had it as a required bool. Aligning to Optional[bool] = None so documents that omit is_time validate correctly.

QMalcolm merged commit 9f6f4f6 into main Jun 2, 2026

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Initial OSI <> dbt Semantic Layer converters#116

Initial OSI <> dbt Semantic Layer converters#116
QMalcolm merged 10 commits into
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QMalcolm commented Apr 29, 2026 •

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