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What's New

This page summarizes the major changes in each release of FHIR4DS.

Version 0.0.2​

April 2026

Version 0.0.2 focuses on reaching full spec compliance, enhancing performance through architectural optimizations and a new C++ extension, and hardening security.

Highlights​

  • Near-Full Spec Conformance: Achieved 99.8% conformance across CQL, DQM, FHIRPath, and ViewDefinition test suites, resolving over 150 identified gaps.
  • 69.5x Performance Boost: Evaluation speed has increased significantly due to a hybrid C++/Python execution model and optimized metadata caching.
  • DuckDB v1.5.2 Integration: Fully stabilized on the latest DuckDB version, including optimized WASM builds for browser-side execution.
  • Standardized Conformance Logging: A new unified logging framework provides detailed pass/fail reporting across all engine components.

Performance Improvements​

  • Registry Caching: MeasureEvaluator now caches FHIR schemas and profile registries, eliminating redundant 1.5MB allocations per evaluation call.
  • Audit Deduplication: Optimized "Full" audit mode to automatically deduplicate Cartesian product results generated by complex LEFT JOINs in retrieve CTEs.
  • C++ Extension Parity: Reached 100% feature parity between the Python UDFs and the high-performance C++ extension, allowing for hybrid execution that combines C++ speed with Python's flexibility.

Security Fixes​

  • JSON Injection Remediation: Fixed critical JSON injection vulnerabilities in the C++ evaluator's type() and width_string() functions.
  • Thread Safety: Added synchronization locks to singleton registries and cache stores (profile_registry, fhir_loader, variable_store) to prevent race conditions in multi-threaded environments.
  • ReDoS Protection: Implemented guards on maximum regex lengths to prevent Regular Expression Denial of Service attacks in string manipulation logic.

Enhancements​

CQL Translator​

  • Point-to-Interval Promotion: Added automatic promotion of point operands to degenerate intervals (e.g., [x, x]) for StartsSame and EndsSame operators to ensure spec-compliant temporal comparisons.
  • Distinct List Aggregates: Added support for standard aggregates (Sum, Min, Max, Avg) on distinct list literals.
  • Clinical UDF Macros: Externalized clinical logic into structured DuckDB macros for better maintainability.

FHIRPath Engine​

  • Cross-Namespace Equivalence: Updated TypeInfo to correctly treat FHIR primitive types and their System equivalents as the same type per FHIRPath §5.1.
  • Conversion Function Flexibility: Support for both functional and member invocation forms for convertsToX functions (e.g., convertsToBoolean(v) and v.convertsToBoolean()).
  • Semantic Temporal Validation: Added strict validation for calendar dates and times, including month day limits and leap year checks.

DQM & ViewDefinition​

  • Enhanced Narratives: Improved narrative generation for population results when detailed evidence capture is disabled.
  • ViewDef String Escaping: Updated the SQL generator to correctly handle backslashes and single quotes within FHIRPath strings in ViewDefinitions.

Infrastructure & Tooling​

  • Centralized Logging: Added a new unified logging framework that tracks pass rates and failure details across all subprojects.
  • Build-Time Auto-Discovery: Improved the build system to auto-discover DuckDB versions and wheel names, ensuring smoother Pyodide package installations.
  • Benchmarking Submodule: Added tests/data/dqm-content-qicore-2026 as a git submodule to provide a standard set of 2026 QI Core measures for benchmarking.

Bug Fixes​

  • CQL: Fixed circular definition handling (QA-019) which previously caused RecursionError in complex libraries.
  • CQL: Fixed Count(distinct(defRef)) producing invalid SQL when referencing non-existent columns.
  • FHIRPath: Resolved a regression in DateTime > Date comparisons.
  • FHIRPath: Fixed type compatibility logic in equality operators to correctly return empty for incompatible types per §6.1.1.
  • ViewDefinition: Fixed a regression in time boundary generation where an unnecessary 'T' prefix was occasionally added.

API Changes​

  • Version Bump: The fhir4ds, fhir4ds.cql, fhir4ds.fhirpath, and fhir4ds.viewdef packages have all been bumped to version 0.0.2.
  • WASM Assets: Updated the required WASM assets; integrations must now use the 0.0.2 translator wheel.

Version 0.0.1​

Initial Release - Early 2026

The initial release established the foundation for the FHIR4DS engine.

  • Unified Interface: Provided a single entry point for CQL, FHIRPath, and ViewDefinition execution.
  • DuckDB Integration: Implemented the first set of Python-based UDFs for FHIR logic.
  • Initial WASM Support: Demonstrated browser-side clinical reasoning using Pyodide and DuckDB-WASM.