HermiT is a conformant OWL 2 DL reasoner that uses the direct semantics. It supports all OWL 2 DL constructs and the datatypes required by the OWL 2 specification.
HermiT is free software: you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.
HermiT is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details.
Copies of the GNU General Public License and the GNU Lesser General Public
License are included in gpl.txt and
lgpl-3.0.txt, respectively. The licenses are also available
from the GNU website.
More information about HermiT and additional licensing information is available from the HermiT website, or by contacting Boris Motik or Ian Horrocks at the Department of Computer Science in the University of Oxford.
HermiT uses the following libraries in unmodified form:
- dk.brics.automaton, copyright © 2001–2009 Anders Møller, released under the BSD license.
- JAutomata, released under LGPL 2.1.
- The OWL API, released under LGPL 3.0.
- Apache Axiom, released under the Apache License 2.0.
- Apache Commons Logging, released under the Apache License 2.0.
The corresponding license files are available in project/lib or in the
Protégé plugin JAR.
The Maven build produces hermit-reasoner-<version>.jar. It can be used from the
command line, as a library in other Java programs, or as a plug-in for Protégé 6.
The source tree contains the HermiT implementation, tests, and examples.
Releases are published to Maven Central by the GitHub Actions publishing workflow. Before creating a release:
- Make sure the Protégé dependency in the
protege6Maven profile refers to a published, non-SNAPSHOT Protégé 6 release. - Run the full test suite and merge the release changes into
main. - Create and publish a GitHub release from the intended commit. Use the Maven
version as the tag, for example
1.5.0, without avprefix. - Check that the Publish packages workflow succeeds, then verify the artifacts
in Maven Central and the generated download URL in
update.properties.
The workflow sets the Maven project version from the release tag, signs the
artifacts, publishes the JAR, sources, Javadocs, and POM, and updates
update.properties on main with the release version and URLs. The metadata is
only updated after publication succeeds. A manually dispatched workflow
publishes the current SNAPSHOT version without changing update.properties.
- supports all of OWL 2
- supports DL-safe SWRL rules
- contains a novel blocking strategy
- minor bug fixes (nominals and equality statements in the ABox were not handled correctly in some case)
- minor bug fixes (nominals and equality statements in the ABox were still not handled correctly if the ontology was nondeterministic, custom data ranges were not loaded correctly in some case)
- minor bug fixes (complex concept queries didn't work properly in the presence of role chains and transitivity), added a progress monitor for realisation that is used by Protege
- several bug fixes (getDisjointObjectProperties(...) and getDisjointDataProperties(...) were not terminating, a null pointer exception in getDataPropertyValues(), language tags were case sensitive, ontology change listener was not removed on dispose), new concept classification algorithm for non-deterministic ontologies, new object property classification, HermiT will now always track changes even when not instantiated as an OWLReasoner, Protege reasoner preferences will be taken into account for the next Protege release
- some bug fixes (bottomObjectProperty encoding corrected, blocking cache cached inactive nodes under single blocking, correct INF/-INF parsing for doubles, no empty node sets in case the next node in the property hierarchy has only inverses), improved property instance retrieval, new disjunction ordering strategy, negative object property assertion encoding no longer requires nominals, command line outputs full IRIs instead of abbreviated ones with HermiT's prefixes, apply changes in non-buffering mode only when needed for a query, data values are stored also with their lexical form, new data property classification
- improved instance handling (class and object property instances, sameAs), new OWL API 3.1, never officially release, but shipped with Protege's beta test version for the new OWL API
- as the inofficial 1.2.5, fixed a null pointer exception in the instance manager
- fixed a bug that caused HermiT to return equivalent properties instead of inverse properties in the method getInverseObjectProperties, automata for complex roles are no longer determinised to safe time, extended explanation example to cover inconsistency explanation, improved disjoint classes code in the materialisation example, anonymous individuals are no longer allowed in OneOf constructs (OWL 2 DL conformance)
- fixed a bug in the classification (in the case of several unsatisfiable classes, HermiT skipped satisfiability tests for some of them and wrongly considered them satisfiable), fixed a bug in object property instance retrieval that left out related individuals if merging has occurred due to number restrictions, made instance manager work also with unknown individuals (fresh entities), complex data ranges are no longer simulated via concepts, but have their own representations to fix a bug with rdfs:Literal
- New bug-fix release of the OWL API is used (3.2.1). Added a method to just write
out axioms for the transitively reduced (class/object property/dataproperty)
hierarchy, much faster than pretty printing but no longer a complete ontology
(missing header and declarations) and not nicely ordered and indented. Only
equivalent classes (properties) are ordered in the according axiom. The
command line by default now just writes out the axioms, but pretty printing can
be enforced with the --prettyPrint argument. Command line interface has been
slightly tidied up and extended.
precomputeInferences() now silently ignores unsupported tasks and disjointClasses and data property assertions are no longer precomputable via the OWLReasoner interface (disj. classes too slow, data property assertions are anyway only using the data property hierarchy and sameAs individuals). Disj. classes can still be precomputed when using HermiT's native interface (Reasoner).
Fixed a bug that sometimes made sameAs computation hang.
- New OWL API is used (3.2.2). Incremental loading and unloading of simple ABoxes (only assertions without complex classes). Fixed an error in the equals method of DateTime (no more unsafe casts), and an error for retrieving direct types of individuals.
- Improved object property classification. Fixed a bug in the detection of clashes involving InternalDatatype objects, and a bug in the instance manager.
- Improved performance of the instance manager for reading off property instances by avoiding double loops. Refactored the clausification of SWRL rules. Fixed a bug in instance manager to properly flush the additional ontology. Fixed a bug in the implementation of the rdf:PlainLiteral datatype. Fixed a bug in the flush() method to check whether the changes were relevant to the import closure of the root ontology. Fixed a problem with absolute IRIs that had <> around the string as officially required, which, however, causes problems in OWL API. Fixed a bug with property chain encoding.
- New OWL API is used (3.4.3). Added new statistics methods in the counting monitor. Changed the Prefixes class so that it uses the terminology from the OWL 2 specification. Added a new library to fix the javax.xml.stream.XMLStreamException error in Protege for malformed XML literals. Improved the handling of owl:topObjectProperty when loading additional axioms (e.g., for entailment checking). Fixed a bug in incremental ABox updates with fresh names. Fixed a bug with core blocking. Fixed a HasKey clausification bug for negated classes. Fixed a bug in the instance retrieval process and a NPE problem when retirving same individuals for an individual that does not exist in the ontology. Fixed a bug in the Protege plugin that is caused by a change to the Protege sources. Fixed some warnings in Java 1.7.
- Fixed a bug where we ignored declared classes/properties after an incremental change. Fixed array index out of bound error for empty property chains.