feat: Add DAX, and examples to the Dialects

[MikeCarlo]

Summary

Related Issues

Checklist

Specification

• Spec changes are included in core-spec/ and follow the existing structure
• Spec changes have been discussed on the mailing list or in a linked issue
• Breaking changes to the spec are clearly called out in the summary

Ontology

• Ontology changes in ontology/ are consistent with spec changes
• New or modified terms are defined and documented

Converters

• Converter logic in converters/ is updated to reflect spec or ontology changes
• New converters include tests under the converter's test directory

Validation

• Validation rules in validation/ are updated if the spec changed
• New validation cases are covered by tests

Documentation

• docs/ is updated to reflect any user-facing changes
• New features or behaviors are documented with examples where appropriate
• CONTRIBUTING.md is updated if the contribution process changed

Examples

• examples/ are added or updated for any new spec constructs or converter support

Tests

• All existing tests pass (pytest / CI green)
• New functionality is covered by tests

Compliance

• ASF license headers are present on all new source files
• No third-party dependencies are added without PMC/IPMC approval

[Copilot]

Pull request overview

This PR extends the core Ossie specification to recognize the DAX (Data Analysis Expressions) dialect and adds/updates examples describing how dialect-specific expressions can be represented.

Changes:

• Add DAX to the standardized dialect enumeration (YAML spec, Markdown spec, and JSON Schema).
• Add DAX to the expression language documentation and provide DAX examples/column in the “Common Dialect Variations” table.
• Add MICROSOFT to the JSON Schema’s vendor example list.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 3 comments.

File	Description
core-spec/spec.yaml	Adds DAX to the dialect enumeration list.
core-spec/spec.md	Documents DAX in the supported dialects table.
core-spec/osi-schema.json	Adds DAX to the dialect enum and adds MICROSOFT as a vendor example.
core-spec/expression_language.md	Adds DAX to standardized dialect identifiers and expands examples/tables to include DAX.

Comments suppressed due to low confidence (2)

core-spec/expression_language.md:671

• In the dialect variation table, the PostgreSQL string concatenation example was changed to CONCAT_WS('', a, b). CONCAT_WS has different NULL-handling (skips NULL arguments) and is less representative of the common Postgres concatenation operator shown elsewhere in the spec (e.g., "||").

| String concat | `CONCAT(a, b)` | `CONCAT(a, b)` | `CONCAT(a, b)` | `CONCAT(a, b)` | `CONCAT_WS('', a, b)` | `CONCATENATE(a, b)` or `a & b` |

core-spec/expression_language.md:670

• In the dialect variation table, the DAX entries for date truncation and date add use STARTOFMONTH/DATEADD, which are table-returning functions in DAX. For a scalar expression example (consistent with the other dialect columns), use scalar date construction/arithmetic instead.

| Date truncation | `DATE_TRUNC('month', d)` | `DATE_TRUNC('month', d)` | `DATE_TRUNC(d, MONTH)` | `DATE_TRUNC('month', d)` | `DATE_TRUNC('month', d)` | `STARTOFMONTH(d)` |
| Date add | `DATEADD(day, 7, d)` | `DATEADD(day, 7, d)` | `DATE_ADD(d, INTERVAL 7 DAY)` | `DATE_ADD(d, 7)` | `d + INTERVAL '7 days'` | `DATEADD(d, 7, DAY)` |

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.