Context

• Align environment variable context propagation name restrictions with POSIX.1-2024 and define normalization behavior. (#4944)
• Decouple the responsibilities of the environment variable propagation carrier. (#4961)
• Remove misleading implementation approach the environment variable propagation. (#5003)
• Change Environment Variables as Context Propagation Carriers document status to Beta. (#5020)

Traces

• Stabilize Tracer enabled operation (#4941)
• Stabilize AlwaysRecord sampler. (#4934)

Metrics

• Add development maxExportBatchSize parameter to Periodic exporting MetricReader. (#4895)

Logs

• Add event to span event bridge. (#5006)

Resource

• Clarify that a Resource describes the observed entity, not the component that technically emits telemetry. (#4905)

Entities

• Define merge algorithm. (4768)

Compatibility

• Deprecate OpenTracing compatibility requirements in the specification. (#4938)
• Stabilize sections of Prometheus and OpenMetrics Compatibility.
  • Stabilize Prometheus Classic Histogram to OTLP Explicit Histogram transformation. (#4874)
  • Stabilize Prometheus Timestamp and Start timestamp transformation. (#4953)
  • Clarify Prometheus Native Histogram to OTLP Exponential Histogram conversion, add conversion rules for Native Histograms with Custom Buckets (NHCB) to OTLP Histogram. (#4898)
  • Stabilize Prometheus Dropped Types transformation. (#4952)
  • Stabilize OpenTelemetry Attributes to Prometheus labels transformation. (#4963)
  • Stabilize Prometheus Exemplar to OpenTelemetry Exemplar transformation. (#4962)
  • Stabilize Prometheus Metadata transformation. (#4954)
  • Stabilize OpenTelemetry Metric Metadata to Prometheus metric metadata. (#4966)
  • Stabilize OpenTelemetry Exemplar to Prometheus Exemplar transformation. (#4964)
• Stabilize sections of Prometheus Metrics Exporter.
  • Stabilize host configuration. (#5025)

SDK Configuration

• Declarative configuration: add in-development guidance for exposing the effective Resource returned by Create. (#4949)
• Require spec changes to consider declarative config schema (#4916)
• Add strict YAML parsing guidance to configuration supplementary guidelines. (#4878)

OTEPs

• Process Context: Sharing Resource Attributes with External Readers. (#4719)
• Support multiple Resources within an SDK. (#4665)

New Contributors

• @fractalwrench made their first contribution in https://github.com/open-telemetry/opentelemetry-specification/pull/4907
• @svencowart made their first contribution in https://github.com/open-telemetry/opentelemetry-specification/pull/4905
• @tiffany76 made their first contribution in https://github.com/open-telemetry/opentelemetry-specification/pull/4958
• @krajorama made their first contribution in https://github.com/open-telemetry/opentelemetry-specification/pull/4898
• @adp2201 made their first contribution in https://github.com/open-telemetry/opentelemetry-specification/pull/4938
• @dbarker made their first contribution in https://github.com/open-telemetry/opentelemetry-specification/pull/4974
• @johannaojeling made their first contribution in https://github.com/open-telemetry/opentelemetry-specification/pull/4969
• @bachp made their first contribution in https://github.com/open-telemetry/opentelemetry-specification/pull/4996
• @iblancasa made their first contribution in https://github.com/open-telemetry/opentelemetry-specification/pull/4949
• @ivoanjo made their first contribution in https://github.com/open-telemetry/opentelemetry-specification/pull/4719

Full Changelog: https://github.com/open-telemetry/opentelemetry-specification/compare/v1.55.0...v1.56.0