6.0.0-M2-release-notes (#5855)

Author: hmottestad

site/content/news/rdf4j-600-M2.md

@@ -0,0 +1,95 @@
+---
+title: "RDF4J 6.0.0 Milestone 2"
+date: 2026-06-05T01:03:37+0200
+layout: "single"
+categories: ["news"]
+---
+Milestone number 2 of the upcoming 6.0.0 release of RDF4J is now available for download.
+
+RDF4J 6.0.0 is a major release of the RDF4J framework. This second milestone continues the work from
+Milestone 1 with RDF 1.2 and SPARQL 1.2 support, new safeguards for long-running queries, query-planning
+improvements, FedX optimizations, and deployment updates.
+
+Please note that RDF4J 6.0.0-M2 requires Java 25.
+
+Some of the highlights covered in this second milestone:
+
+- RDF 1.2 and SPARQL 1.2 support in parsers, writers, the model API, and query evaluation
+- Query circuit breakers that protect server and workbench query execution under unsafe JVM memory pressure
+- Configurable slow-query logging for Sail-backed repositories, focused on time to first result
+- FedX grouped source selection, reducing remote source-selection requests for larger federations
+- Query optimizer work including sketch-based join planning, cascade-style planners, LMDB cardinality-estimation
+  improvements, and plan-comparison tooling
+- Updated Docker images for Jetty 12 and Tomcat 11 on Java 25, plus Docker run documentation updates
+- New vocabulary modules for EU, annotation, and bibliographic vocabularies, plus additional PROV-O inverse properties
+
+This milestone build is not yet feature-complete, but we are putting it out to receive early feedback on all the
+improvements we have put in.
+
+<!--more-->
+
+ - [issues fixed in 6.0.0 Milestone 2](https://github.com/eclipse-rdf4j/rdf4j/issues?q=is%3Aissue+label%3AM2+is%3Aclosed+milestone%3A6.0.0)
+ - [issues planned for 6.0.0](https://github.com/eclipse-rdf4j/rdf4j/milestone/128)
+
+## Upgrade notes
+
+### RDF 1.2 and SPARQL 1.2
+
+RDF4J 6.0.0-M2 adds broad support for RDF 1.2 and SPARQL 1.2
+([GH-5327](https://github.com/eclipse-rdf4j/rdf4j/issues/5327)).
+This includes RDF 1.2 parser and writer updates for Turtle, TriG, N-Triples, N-Quads, and RDF/XML, SPARQL 1.2 grammar
+and evaluation changes, and conformance-test coverage for the new syntax and behavior.
+
+The model API now uses RDF 1.2 triple-term terminology. Legacy RDF-star parser/writer formats and names have been
+replaced by the corresponding triple-term APIs and formats. Triple terms are supported in object position, matching
+RDF 1.2 semantics.
+
+Support is not yet complete for every store. The SPARQL 1.2 conformance suite is enabled for MemoryStore, while
+NativeStore and LMDBStore still have known gaps for triple-term and base-direction support.
+
+### Query execution safeguards
+
+RDF4J now includes query circuit breakers for server and workbench query execution
+([GH-5809](https://github.com/eclipse-rdf4j/rdf4j/issues/5809)). These monitor JVM memory pressure, reject or abort
+query work when pressure becomes unsafe, release in-flight query resources, and expose breaker status for operators.
+
+Sail-backed repositories can also be configured to log slow queries
+([GH-5819](https://github.com/eclipse-rdf4j/rdf4j/issues/5819)). The implementation tracks query context through
+Sail evaluation and logs queries that exceed a configured threshold before producing their first result.
+
+### Query planning and LMDB
+
+The query optimizer has received new sketch-based, unified, and cascade-style planning work
+([GH-5720](https://github.com/eclipse-rdf4j/rdf4j/issues/5720),
+[PR-5785](https://github.com/eclipse-rdf4j/rdf4j/pull/5785),
+[PR-5796](https://github.com/eclipse-rdf4j/rdf4j/pull/5796)), including runtime telemetry and plan-comparison
+tooling. LMDB cardinality estimation has also been improved with a page-walking estimator that reads LMDB data files
+directly ([GH-5686](https://github.com/eclipse-rdf4j/rdf4j/issues/5686)).
+
+### FedX
+
+FedX source selection can now group remote source checks per endpoint
+([GH-5813](https://github.com/eclipse-rdf4j/rdf4j/issues/5813)). For larger federations, this reduces source-selection
+round trips from one ASK query per statement-pattern/endpoint pair to grouped SELECT queries using
+`BIND(EXISTS { ... })`.
+The optimization is enabled by default and can be disabled through `FedXConfig#withEnableGroupedSourceSelection(false)`.
+
+The FedX module also received cleanup for deprecated and unwired 6.0-era code paths
+([GH-5828](https://github.com/eclipse-rdf4j/rdf4j/issues/5828)).
+
+### Docker and deployment
+
+The Docker setup now targets Java 25 application-server images: Jetty 12 with EE11 modules and Tomcat 11
+([GH-5801](https://github.com/eclipse-rdf4j/rdf4j/issues/5801)). The developer testing guide and Server/Workbench
+deployment guide now document the `docker/run.sh` workflow and Docker Compose usage.
+
+### Vocabularies
+
+RDF4J now ships additional vocabulary modules for EU data-portal and dataspace vocabularies, annotation vocabularies,
+and bibliographic vocabularies ([GH-5709](https://github.com/eclipse-rdf4j/rdf4j/issues/5709)). The PROV-O vocabulary
+also includes the suggested inverse properties listed by PROV-O
+([GH-5706](https://github.com/eclipse-rdf4j/rdf4j/issues/5706)).
+
+### Links
+
+- [Download RDF4J](/download/)