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Top-level ontology for scientific data integration. ISO/IEC 21838-2 standard. Foundation for 500+ OBO Foundry ontologies.

Foundational ontology capturing categories underlying natural language and human common sense.

One of the earliest and most comprehensive foundational ontologies with thousands of terms. IEEE-owned.

Integrates GFO, DOLCE, and OntoClean. Theoretical basis for the OntoUML conceptual modeling language.

Top-level ontology integrating objects and processes. Covers time, space, properties, relations, roles, and situations.

Foundational ontology focusing on qualities, processes, and events. Continuously refined since 1999.

Minimalist upper ontology for enterprise knowledge graphs. Maximum business coverage with fewest primitives.

High-level ontology for cultural heritage data using event-based modeling. ISO 21127:2023 standard.

Physics-based top-level ontology for materials science with ~6000 concepts covering modelling, characterization, and processing.

Open ontologies built on BFO for manufacturing and engineering. Data interoperability in industrial domains.

Standard for data modeling and interoperability in process plants using Semantic Web. Upper ontology plus reference data.

Largest open collaboratively edited multilingual knowledge graph with 100M+ items. Structured data backbone for Wikipedia.

Structured knowledge from Wikipedia. 768 classes, 3000+ properties, 4.58M+ entities in English across 125 languages.

Large semantic knowledge graph from Wikipedia, WordNet, Wikidata. 17M+ entities, 150M+ facts with high precision.

Open multilingual knowledge graph of common sense knowledge in 73 languages. Powers ConceptNet Numberbatch embeddings.

Large lexical database with ~117,000 synsets linked by semantic and lexical relations. Foundation of computational linguistics.

Geographical database with 25M+ names and 12M+ unique features. RDF/Linked Data for geographic entities worldwide.

Shared vocabulary for structured data markup. 800+ types, 1400+ properties understood by Google, Bing, Yahoo, Yandex.

Core data model for the Semantic Web. Subject-predicate-object triples. Foundation of all semantic web technologies.

Logic-based language for rich ontologies. Complex class descriptions, restrictions, and automated reasoning.

W3C standard for thesauri, classification schemes, taxonomies, and controlled vocabularies.

Query language for RDF databases. Retrieval and manipulation of knowledge graph data via endpoints.

OWL2 ontology for provenance — entities, activities, and agents. Tracks data lineage and audit trails.

Language for validating RDF graphs against conditions (shapes). W3C standard for data quality.

Metadata vocabulary for describing resources. 15 core elements (title, creator, subject) expanded to dozens of terms.

Ontology describing persons, their activities, and relations. Enables decentralized social network description.

Joint W3C/OGC ontology for sensors, observations, sampling, and actuation. Core of IoT semantic standards.

RDF vocabulary for datasets and data services in catalogs. Powers open data portals and dataset discovery.

Most comprehensive clinical terminology with 350,000+ concepts. Global standard for electronic health records.

Modern standard for healthcare data exchange. RESTful API approach with 150+ resource types.

Universal standard for lab tests and clinical observations. ~100,000 terms for lab, clinical, and surveys.

NLM's controlled vocabulary for biomedical literature. ~30,000 descriptors. Powers PubMed search.

Most widely used bioinformatics ontology. Gene products described by molecular functions, biological processes, cellular components.

Dictionary of molecular entities focused on small chemical compounds. 60,000+ entities with structures and roles.

Standardized vocabulary of phenotypic abnormalities. 16,000+ terms critical for rare disease diagnosis.

Standard for biological pathway data — metabolic, signaling, gene regulatory pathways.

Comprehensive semantic model of financial instruments, legal entities, business processes. OMG standard.

Language for cyber threat intelligence. Threat actors, campaigns, indicators, malware, attack patterns.

Knowledge base of adversary tactics and techniques. 200+ techniques across Enterprise, Mobile, ICS matrices.

Knowledge graph of cybersecurity countermeasures. Maps defensive techniques to adversary behaviors.

ETSI standard reference ontology for smart applications. Extensions for energy, environment, buildings.

Open-source ontology for buildings and subsystems. HVAC, lighting, electrical systems.

OGC standard for geospatial data in RDF plus SPARQL spatial query extensions.

Systematic ontology of AI concepts — deep learning, ML tasks, biases, architectures in 8 branches.

W3C community schema with 25 core classes for ML algorithms, datasets, and experiments.

RDF/OWL format for NLP tool interoperability. Text, annotations, and linguistic resources as linked data.

W3C decentralized social networking protocol. Powers Mastodon, Pixelfed, PeerTube (the Fediverse).

IEEE 1872-2015 standard defining core robotics concepts — robots, systems, environments, tasks.

Open standard for software bill of materials (SBOM), license compliance, security. ISO 5962:2021.

Ontology for Ethereum blockchain — accounts, blocks, transactions, smart contracts.

Open ontology for energy domain — carriers, technologies, models, scenarios for energy system analysis.

Controlled vocabularies for news industry. 1,100+ media topic concepts for categorizing news.

RDF framework for cultural heritage objects. 60M+ objects from 4,000+ European institutions.

Long-term AI project (since 1984) with ~1.5M terms and ~24.5M assertions of common sense knowledge.

Lightweight upper-level ontology (OWL Light) for entity recognition, semantic annotation, and information extraction.

Foundation ontology for broad general semantic interoperability across heterogeneous knowledge domains.

Abstract upper-level ontology for archaeological and cultural heritage data management and integration.

Largest multilingual encyclopedic dictionary with 20M+ entries across 500 languages. Unifies WordNet, Wikipedia, Wikidata.

Integrates 7 knowledge bases (Wikipedia, Wikidata, Schema.org, DBpedia, GeoNames, OpenCyc, UNSPSC) into 58K+ concepts.

CMU knowledge base that continuously learns facts from the web using semi-supervised ML. Auto-extracts structured knowledge.

Google's proprietary knowledge graph powering Knowledge Panels in search. Read-only API available.

Basic elements for describing ontologies — classes, subclass hierarchies, properties, domains, and ranges using RDF.

OWL-DL ontology of temporal concepts — instants, intervals, durations, temporal relations. W3C/OGC standard.

Ontology for physical quantities, units of measure, dimensions, and data types. Essential for scientific data.

Ontology for books, articles, documents on the semantic web. Citation metadata for libraries and publishers.

Suite of OWL 2 ontologies for scholarly publishing — citations, references, document structure, roles.

OWL ontology for e-commerce: products, offers, prices, stores. Largely integrated into Schema.org.

RDF vocabulary for metadata about RDF datasets — statistics, access points, and interlinking information.

Core ontology for organizational structures — hierarchies, roles, memberships, sites. Widely used in government data.

Ontology for online communities — forums, wikis, blogs. Semantic integration across community platforms.

Ontology for academic communities — researchers, publications, grants, courses, departments.

RDF ontology for contact information — people, organizations, addresses, phone numbers, emails.

WHO standard for coding diagnoses and health conditions. ~70,000 codes. Mandated for US medical billing.

Standardized nomenclature for clinical drugs. Normalized names linking drug vocabularies for medication interoperability.

Integrative framework unifying 200+ biomedical vocabularies. Cross-mappings via Metathesaurus with 4M+ concepts.

International terminology for pharmaceutical regulatory communication. Adverse event reporting and drug safety.

Reference terminology for cancer research. 160,000+ concepts covering diseases, drugs, anatomy, genes.

Common Data Model standardizing observational health data. Powers OHDSI network across 100+ databases globally.

International standard for medical imaging data. Formats, protocols, and data model for imaging workflow.

Suite of standards (CDASH, SDTM, ADaM) for clinical trial data. FDA-endorsed for regulatory submissions.

Standardized ontology for human disease terms. Maps across MeSH, ICD, SNOMED, and OMIM.

Cross-species anatomy ontology covering anatomical structures in animals. Bridges species-specific anatomies.

Ontology for life-science investigations — study designs, protocols, instruments, data, analyses.

Ontology for environments — biomes, environmental features, materials. Links organisms to habitats.

Structured vocabulary for cell types in animals. Covers 30+ organ systems with lineage relationships.

Controlled vocabulary for genomic annotation. Features and attributes of biological sequences.

Curated classification of all organisms in NCBI sequence databases. 2.4M+ taxa from all domains of life.

Application ontology for experimental variables. Combines parts of ontologies to describe experimental designs.

Ontology of bioinformatics operations, data types, formats, and topics. Powers bio.tools registry.

Vocabulary describing plant anatomy, morphology, and developmental stages across green plants.

Global framework for business/financial reporting. Mandated by SEC. OWL/RDF ontology representation available.

Standard for OTC derivatives and structured products. Industry standard for trade processing.

Vocabulary for product data using GS1 global standards (barcodes, GTINs). Powers global supply chain identification.

International standard for products and services. 45,000+ classes across 40+ industries for procurement.

Global classification for products in procurement. 5-level hierarchy used by governments worldwide.

Ontology for manufacturing entities — products, processes, resources, and their interrelations.

Standard for enterprise-control system integration in manufacturing. Production, quality, inventory, maintenance.

Open modeling language for enterprise architecture. Business, application, and technology layer representation.

Ontology for legal knowledge — concepts, norms, rules, and legal reasoning.

OASIS standard for parliamentary, legislative, and judiciary documents in XML.

System for identifying and accessing EU and national legislation online with unique URIs.

EU classification of 3,000+ occupations and 13,000+ skills in 27 languages.

US national education data standards. 1,700+ data elements from early childhood through workforce.

Standard for public contracting data — planning, tender, award, and implementation stages.

FAO thesaurus for agriculture, forestry, fisheries, food. 40,000+ concepts in 40+ languages.

Modular ontology suite with ~6,000 concepts in ~200 ontologies covering Earth system science.

OGC standard for 3D city models. Buildings, terrain, vegetation, water, and transportation.

Ontology for statistical methods, tests, variables, and their relationships in research.

Dictionary of publicly disclosed vulnerabilities. Unique CVE IDs for cross-referencing worldwide.

Community list of 900+ software and hardware weakness types organized hierarchically.

Dictionary of known attack patterns describing how adversaries exploit weaknesses.

Community ontology for cyber investigation and cybersecurity domains. Foundation for CASE ontology.

W3C standard for describing IoT device interfaces. Machine-readable properties, actions, and events.

Suite of harmonized data models for smart cities and IoT. 60+ domains from parking to water quality.

W3C-LBD ontology for building topology — sites, buildings, storeys, spaces, interconnections.

RDF vocabulary for music — artists, albums, tracks, performances, compositions, and audio signals.

W3C model for lexical information relative to ontologies. Standard for linguistic linked data publishing.

International standard for social/behavioral/health science data. Full data lifecycle metadata.

Comprehensive model for electricity network data. Grid topology, equipment, markets, SCADA.

Knowledge processing system for autonomous robots. Combines ontological knowledge with sensor data.