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.
• 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.
• 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.

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.
• WIDOCO - Java tool for publishing and creating an enriched and customized documentation of ontology automatically, by following a series of steps in a GUI. Based on LODE.
• 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.
• BioPortal - A comprehensive repository of biomedical ontologies.
• KBS/Ontology Projects Worldwide - A List of 300+ ontologies and related resources, maintained by Peter Clark.
• The Linked Open Data Cloud
• Linked Open Vocabularies
• prefix.cc - Namespace lookup for RDF developers.
• BARTOC (Basel Register of Thesauri, Ontologies & Classifications) - Database of Knowledge Organization Systems and KOS related Registries, developed by the Basel University Library, Switzerland.
• DBpedia Archivo - Ontology archive automatically indexing OWL ontologies on the web.
• http://www.ontologydesignpatterns.org/ont/ in OntologyDesignPatterns.org (ODP)

Archived or inactive:

• Ontology List by Ying Ding.
• Protege Ontology Library in Protege Wiki - Listing 100+ ontologies.

• 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.
• gist - Semantic Arts' minimalist upper ontology for the enterprise.
• 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.

• Digital Buildings Ontology (DBO) - Ontology for buildings and building-installed equipment by Google.

• 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 (Java)
• FunOWL - A Python library for working with OWL (functional syntax). (Python)
• Horned OWL - An OWL Rust library. (Rust)
• ontor - Ontology editing library built on Owlready2. (Python)
• OWL API - A Java API for creating, manipulating and serializing OWL Ontologies. (Java)
• Owlish - A Rust library for working with OWL 2 ontologies with Wasm support and turtle parsing. (Rust)
• Owlready2 - A module for ontology-oriented programming in Python. (Python)
• Tawny-OWL - A domain-specific language and library for OWL ontologies in Clojure. (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).