A curated list of ontology things. Your contribution is welcome!

• Ontology Editors
• Ontology Utilities
• Datastore
• Languages
• Ontologies and Vocabularies
  • Upper-level
  • Mid-level
  • Cross-domain
  • Domain
  • Vocabularies
• Alignment & Matching
• Logics
• Reasoners
• Querying
• Rule and Schema Definition
• Programming
• Communities
• Related

• Eddy - A graphical editor for the specification and visualization of ontologies in Graphol format.
• Fluent Editor - An award winning comprehensive tool for editing and manipulating complex ontologies that uses Controlled Natural Language.
• OntoME - Designed for any object-oriented structured data model to build, manage and align your ontology, or to simply browse through the existing ontologies. (GitHub for issues)
• OntoStudio (formerly OntoEdit) - A most widespread commercial modeling environment for creating and maintaining ontologies.
• OWLGrEd - A UML Style Graphical Editor for OWL.
• Protégé - A free, open-source ontology editor and framework for building intelligent systems.
• Vitro - A general-purpose web-based ontology and instance editor with customizable public browsing.
• VocBench and Semantic Turkey - VocBench is a web-based, multilingual, collaborative development platform for managing OWL ontologies, SKOS(/XL) thesauri, Ontolex-lemon lexicons and generic RDF datasets. Its backend, Semantic Turkey is a RDF service platform for Knowledge Management and Acquisition.
• Termboard - A very simple graphical editor to create Terms and Relations. It can use ChatGPT, Google Bard or any other chatbot. Ideal for beginners wanting to make and share quick sketches.

Archived or inactive:

• Apollo (last updated ~2005) - A user-friendly knowledge modelling application.
• NeOn Toolkit (last updated 2011) - A state-of-the-art, open source multi-platform ontology engineering environment, which provides comprehensive support for the ontology engineering life-cycle.
• Knoodl (last updated ~2017) - An ontology-driven "Distributed Information Management System" (DIMS) by Revelytix, Inc.
• SWOOP (last updated 2007) - An OWL Ontology browser/editor that takes the standard Web browser as the basic UI paradigm.
• TopBraid Composer Series (archived ~2021) - A powerful Integrated Development Environment (IDE) for implementing Knowledge Graph/Linked Data services by TopQuadrant, Inc.
• WebODE (discontinued in 2006) - An extensible ontology-engineering suite based on an application server.

See also:

• List of ontology editors in Wikipedia
• A List of Ontology Engineering Tools (Ontology Editors) by the Hozo group

• LODE - Java ontology documentation generator to convert OWL ontologies into HTML human-readable pages.
• OAK - The Ontology Access Kit, a python library and command line tool for ontologies.
• obonet - Python library to convert OBO-formatted ontologies to networkx graphs.
• OnToology - Online tool to automatically generate documentation and evaluation for Ontologies hosted on GitHub.
• Ontospy - Python library and command-line interface for inspecting and visualizing RDF models.
• OWLTools - Java API and command-line utilities on top of the OWL API.
• pyLODE - Python ontology documentation generator inspired by LODE.
• pyontutils - Python utilities for working with ontologies.
• ROBOT - Java library and CLI tool for working with ontologies, particularly Open Biomedical Ontologies. It also provides a bridge to Python by Py4J.
• WebVOWL - Web application for visualizing ontologies on the Web.
• yamlpyowl - Python based YAML-to-OWL-converter.
• owl-cli - Command line tool for ontology engineering (diagram generation, read/write documents in various formats and OWL DL reasoning).

Generic RDF tools:

• Tarql - Python tool to turn CSV into RDF using SPARQL syntax.
• VocPrez - Python tool (API and web front-end) for the read-only delivery system of SKOS vocabularies.

• SciGraph - Neo4j backed ontology store.

• Common Logic (CL) - A language with an abstract syntax and semantics which are given in the ISO standard.
  • Common Logic Interchange Format (CLIF)
  • Conceptual Graph Interchange Format (CGIF)
  • eXtended Common Logic Markup Language (XCL)
• CycL - A language with a concrete syntax based on first-order predicate calculus and Lisp.
• Knowledge Interchange Format (KIF) -
• OBO Format (OBOF) - A language used in the OBO Foundry with a concrete syntax and semantics which maps the language to OWL2-DL.
• OWL 2 Web Ontology Language - A language with an abstract syntax and semantics. It has a few defined (reserved) vocabulary terms (see 2.4, Table 3 and 2.2). The language is compatible with RDF by the mapping between the OWL 2 language and the RDF language. It can be extended with Description Logics (see Logics).
  • Manchester Syntax
  • OWL/XML
• RDF (Resource Description Framework) 1.1 - A language with an abstract syntax (a data model) based on the subject-predicate-object triple and semantics. For no vocabulary is defined in itself, it is used with RDF Schema vocabulary (see Vocabularies).
  • HDT (2010~)
  • JSON-LD (2010~)
  • Notation3 (N3) (2008~)
  • N-Quads (2014~)
  • N-Triples (2001/2014~)
  • RDFa (2004~)
  • RDF/XML (2002/2004~)
  • TriG (2007/2014~)
  • TriX (2004~, inactive)
  • Turtle (2004/2014~)
  • RDF* (generic extension of RDF, 2019~)

Archived or inactive:

• KL-ONE
• Loom
• Nanotation (2014, inactive)

See also:

• Logics section of this list
• Ontology language in Wikipedia

See also:

• Lists of ontologies in W3C Wiki - A short meta-list of lists of ontologies.
• Ontology List by Ying Ding.
• Protege Ontology Library in Protege Wiki - Listing 100+ ontologies.
• KBS/Ontology Projects Worldwide - A List of 300+ ontologies and related resources, maintained by Peter Clark.
• Linked Open Vocabularies -
• prefix.cc - Namespace lookup for RDF developers.
• The Linked Open Data Cloud -
• BARTOC (Basel Register of Thesauri, Ontologies & Classifications) - Database of Knowledge Organization Systems and KOS related Registries, developed by the Basel University Library, Switzerland.
• http://www.ontologydesignpatterns.org/ont/ in OntologyDesignPatterns.org (ODP)

• BFO (Basic Formal Ontology) - A small, upper level ontology that is designed for use in supporting information retrieval, analysis and integration in scientific and other domains.
• DBpedia Ontology - A shallow, cross-domain ontology, which has been manually created based on the most commonly used infoboxes within Wikipedia.
• DOLCE (Descriptive Ontology for Linguistic and Cognitive Engineering) - A foundational ontology originally developed in WonderWeb project. (old page)
• GFO (General Formal Ontology) - A top-level ontology for conceptual modeling, which is being constantly further developed by Onto-Med.
• KYOTO 3 Top - An ontology which extends DOLCE-Lite Plus (DLP). It consists of ~50 classes.
• SUMO (Suggested Upper Merged Ontology) -
• YAMATO (Yet Another More Advanced Top-level Ontology) -

Archived or inactive:

• UMBEL (Upper Mapping and Binding Exchange Layer) Vocabulary (UMBEL ontology) (merged to KBpedia in 2019) - An ontology consists of ~70 classes.

• KYOTO 3 Middle - An ontology which consists of ~350 classes.
• MILO (Mid-Level Ontology) in SUMO -
• UMBEL (Upper Mapping and Binding Exchange Layer) Reference Concepts (Reference Concepts ontology) -

• ConceptNet - An open, multilingual knowledge graph.
• Cyc (OpenCyc/ResearchCyc) - A knowledge base which contains more than 630,000 concepts.
• DBpedia - A crowd-sourced community effort to extract structured content from the information created in various Wikimedia projects.
• KBpedia - A comprehensive knowledge structure for promoting data interoperability and knowledge-based artificial intelligence (KBAI). It combines Wikipedia, Wikidata, schema.org, DBpedia, GeoNames, OpenCyc, and UMBEL.
• Mosaic Knowledge Graphs - ATOMIC + ConceptNet combination by AllenAI.
• NELL ontology and knowledge base - An ontology developed by the Never-Ending Language Learning (NELL) project.
• Wikidata - A free and open knowledge base that can be read and edited by both humans and machines. It contains more than 55,000,000 data items.
• WordNet - A large lexical database of English. It consists of ~117,000 synsets (groups of synonyms).
• YAGO - A huge semantic knowledge base, derived from Wikipedia WordNet and GeoNames. It has knowledge of more than 10 million (10,000,000) entities.
• Xlore - A large-scale multilingual knowledge graph by structuring and integrating Chinese Wikipedia, English Wikipedia, French wikipedia, and Baidu Baike.

Without explicit classes:

• Billion Triple Challenge (BTC) 2019 Dataset - A result of a large-scale RDF crawl (accepting RDF/XML, Turtle and N-Triples) conducted from 2018/12/12 until 2019/01/11 using LDspider.

Archived or inactive:

• Freebase (shut down in 2016) -
• MindNet (~2001?) - ... by Microsoft.
• SENSUS -
• Mikrokosmos -

See also:

• Open Multilingual Wordnet - A list of open wordnets in a variety of languages, all linked to the Princeton WordNet of English (PWN).

• KYOTO 3 Domain - An ontology which consists of ~1900 classes.

• Gene Ontology (GO) - The world’s largest source of information on the functions of genes.
• Uberon - All body parts across all animals.

• GoodRelations - The Web vocabulary for e-commerce.
• Product Types Ontology - High-precision identifiers for product types based on Wikipedia.

• SIOC (Semantically Interlinked Online Communities) - An ontology of terms that can be used to describe online communities on the Web of Data.

• CIDOC CRM (Conceptual Reference Model) - An ontology for cultural heritage information, which describes the explicit and implicit concepts and relations relevant to the documentation of cultural heritage.

• Wine Ontology - An example used in W3C OWL Guide.
• Food Ontology - An example used in W3C OWL Guide.
• FoodOn - An ontology built to interoperate with the OBO Library and to represent entities which bear a "food role".

• Geographical Entity Ontology - An ontology of geographical entities implemented in OWL 2 and based on Basic Formal Ontology (BFO).

See:

• CLARIAH/awesome-humanities-ontologies - A curated list of ontologies for Digital Humanities.

See:

• Liquid-Legal-Institute/Legal-Ontologies - A list of selected resources, methods, and tools dedicated to legal data schemes and ontologies.

• rNews - An approved standard for using semantic markup to annotate news-specific metadata in HTML documents.

• Friend Of A Friend (FOAF) - A computer language defining a dictionary of people-related terms that can be used in structured data.
• vCard Ontology - An ontology for describing people and organizations. A mapping of the vCard specification (RFC6350) to RDF/OWL.

A vocabulary is a set of terms for a language.

• Dublin Core Metadata Element Set - A vocabulary of fifteen properties for use in resource description.
• DCMI Metadata Terms - An extension of the Dublin Core Metadata Element Set.
• IMI (Infrastructure for Multilayer Interoperability) Core Vocabulary - A Japanese controlled vocabulary consists of roughly 60 class concepts, 250 property concepts and words associated to them.
• Open Graph protocol -
• RDF Schema (RDFS) 1.1 - A data-modelling RDF vocabulary used for defining RDF vocabularies.
• Schema.org Schemas -
• SKOS (Simple Knowledge Organization System) - An RDF vocabulary for representing semi-formal knowledge organization systems (KOSs), such as thesauri, taxonomies, classification schemes and subject heading lists.

• AgreementMakerLight (AML) - Ontology matching system developed by LASIGE (FCUL, Portugal) in collaboration with the ADVIS Lab (UIC, USA).
• LogMap - Highly scalable ontology matching system with "built-in" reasoning and inconsistency repair capabilities.
• OntoEMMA - Ontology matcher by AllenAI.

See also:

• Ontology Matching website - Hosting OM (International Workshop on Ontology Matching) and OAEI (Ontology Alignment Evaluation Initiative).
• Alignment API - Ontology Alignment API specification. (implemented in Java)

A logic is a language with a proof theory (e.g., axioms and inference rules).

• Description Logics (DLs) -
• F-Logic family -

See also:

• Description Logic Complexity Navigator by Evgeny Zolin

A reasoner is a program which infers explanatory or new facts and detects inconsistencies in ontology and knowledge base based on the logic associated.

• CEL - A lightweight Description Logic (EL+) reasoner for large-scale biomedical ontologies. (Common Lisp+Java)
• ELK - An ontology reasoner that aims to support the OWL 2 EL profile. (Java)
• EYE - A reasoning engine which performs semibackward chaining and supports Euler paths. (Prolog)
• FaCT++ - The new generation of the well-known FaCT OWL-DL reasoner which uses optimised tableaux algorithms. (C++)
• Flora-2 (Ergo Lite) - A F-logic based reasoning system. (Prolog)
• HyLAR - A rule-based incremental reasoner for the Web. (JavaScript)
• jcel - A reasoner for the description logic EL+. (Java)
• Openllet - An OWL DL reasoner build on top of Pellet 2. (Java)
• OWL-RL - A simple implementation of the OWL2 RL Profile, as well as a basic RDFS inference, on top of RDFLib. (Python)
• pyfactxx - Python bindings for upgraded FaCT reasoner and RDFLib integration. (Python/C++)
• Racer - A knowledge representation system that implements a highly optimized tableau calculus for the description logic SRIQ(D). (Common Lisp+Java)
• Whelk - A Scala OWL reasoner based on the algorithm implemented in ELK, using immutable data structures.

Archived or inactive:

• cwm (last updated 2005) - A forward chaining RDF reasoner. (Python)
• HermiT (last updated ~2013) - The first publicly-available OWL reasoner based on a novel “hypertableau” calculus which provides much more efficient reasoning than any previously-known algorithm. (Java)
• Hoolet (last updated 2004) - An implementation of an OWL-DL reasoner that uses a first order prover. It uses the Vampire prover for reasoning purposes. Other reasoners could also be used; communication with the reasoner is via the TPTP format which is understood by a number of theorem provers.
• KAON2 reasoner (last updated 2008) - A DL reasoner for the SHIQ(D) subset of OWL-DL, based on novel algorithms which reduce a SHIQ(D) knowledge base to a disjunctive datalog program. (proprietary, Java)
• Pellet 2 (last updated ~2015) - An open source OWL DL reasoner for Java. Pellet 3 (proprietary) is embedded in the Stardog platform. (Java)

See also:

• How does a reasoner work? - An introductory article by Uli Sattler, Robert Stevens, and Phillip Lord

• DL Query (class expression) - A query language supported by the DL Query tab plugin for Protégé based on the Manchester OWL syntax.
• SPARQL 1.1 - A set of specifications that provide languages and protocols to query and manipulate RDF graph content on the Web or in an RDF store.
  • SPARQL-DL - A substantial subset of SPARQL that can be covered by the standard reasoning services OWL-DL reasoners provide. It is implemented in the Pellet reasoner.
  • SPARQL-OWL algorithm - A sound and complete algorithm for answering SPARQL-OWL, SPARQL queries under the OWL 2 Direct Semantics entailment regime.
  • SPARQL* - An RDF*-aware extension of the RDF query language SPARQL.

See also:

• [protege-user] which is the best query language for owl ontologies?

• LinkML - A polymorphic semantic modeling language.
• SHACL (Shapes Constraint Language)
• ShEx (Shape Expressions)
• SWRL (Semantic Web Rule Language) - A rule markup language which extends the logical expressivity of the OWL language.

Archived or inactive:

• SPIN (SPARQL Inferencing Notation) (virtually succeeded by SHACL, see From SPIN to SHACL)

See also: Ontology Utilities section.

• Apache Jena Ontology API -
• FunOWL - A Python library for working with OWL (functional syntax).
• Horned OWL - An OWL Rust library
• ontor - Ontology editing library built on Owlready2. (Python)
• OWL API - A Java API for creating, manipulating and serializing OWL Ontologies.
• Owlready2 - A module for ontology-oriented programming in Python.
• Tawny-OWL - A domain-specific language and library for OWL ontologies in Clojure.

Archived or inactive:

• OPPL - An abstract formalism that allows for manipulating ontologies written in OWL.

• Ontology Alignment Evaluation Initiative (OAEI)
• Association for Ontology Design & Patterns (ODPA)

• semantalytics/awesome-semantic-web - A curated list of various semantic web and linked data resources.
• jbenner-radham/awesome-semantic-web - A curated list of various semantic web and linked data resources.
• totogo/awesome-knowledge-graph - A curated list of Knowledge Graph related learning materials, databases, tools and other resources.
• Materials-Data-Science-and-Informatics/awesome-fair-data - A curated list of awesome stuff around the FAIR principles for (scientific) data, i.e that data is findable, accessable, interoperable and re-usable.
• pysemtec/semantic-python-overview - A (subjective) overview of projects which are related both to python and semantic technologies (RDF, OWL, Reasoning, ...).

Archived or inactive:

• buaaliuming/Awesome-Knowledge-Bases - Available knowledge bases, Ontology, Knowledge Graph or taxonomy.
• costezki/awesome-semantic-tools - List of projects related to Ontology engineering and Semantic Web technologies that make a geek smile for they exist.
• KMax/awesome-semantic-web-business - A curated list of awesome resources that feature usages of Semantic Web technologies in business cases (applications).