The Web Ontology Language (OWL) is a family of
knowledge representation
Knowledge representation and reasoning (KRR, KR&R, KR²) is the field of artificial intelligence (AI) dedicated to representing information about the world in a form that a computer system can use to solve complex tasks such as diagnosing a medic ...
languages for authoring
ontologies
In computer science and information science, an ontology encompasses a representation, formal naming, and definition of the categories, properties, and relations between the concepts, data, and entities that substantiate one, many, or all domains ...
. Ontologies are a formal way to describe taxonomies and classification networks, essentially defining the structure of knowledge for various domains: the nouns representing classes of objects and the verbs representing relations between the objects.
Ontologies resemble
class hierarchies in
object-oriented programming
Object-oriented programming (OOP) is a programming paradigm based on the concept of "objects", which can contain data and code. The data is in the form of fields (often known as attributes or ''properties''), and the code is in the form of pr ...
but there are several critical differences. Class hierarchies are meant to represent structures used in source code that evolve fairly slowly (perhaps with monthly revisions) whereas ontologies are meant to represent information on the Internet and are expected to be evolving almost constantly. Similarly, ontologies are typically far more flexible as they are meant to represent information on the Internet coming from all sorts of heterogeneous data sources. Class hierarchies on the other hand tend to be fairly static and rely on far less diverse and more structured sources of data such as corporate databases.
The OWL languages are characterized by
formal semantics. They are built upon the
World Wide Web Consortium
The World Wide Web Consortium (W3C) is the main international standards organization for the World Wide Web. Founded in 1994 and led by Tim Berners-Lee, the consortium is made up of member organizations that maintain full-time staff working to ...
's (W3C) standard for objects called the
Resource Description Framework The Resource Description Framework (RDF) is a World Wide Web Consortium (W3C) standard originally designed as a data model for metadata. It has come to be used as a general method for description and exchange of graph data. RDF provides a variety of ...
(RDF). OWL and RDF have attracted significant academic, medical and commercial interest.
In October 2007,
a new W3C working group was started to extend OWL with several new features as proposed in the OWL 1.1 member submission. W3C announced the new version of OWL on 27 October 2009.
This new version, called OWL 2, soon found its way into semantic editors such as
Protégé
Mentorship is the influence, guidance, or direction given by a mentor. A mentor is someone who teaches or gives help and advice to a less experienced and often younger person. In an organizational setting, a mentor influences the personal and p ...
and
semantic reasoners such as Pellet, RacerPro, FaCT++ and HermiT.
The OWL family contains many species, serializations, syntaxes and specifications with similar names. OWL and OWL2 are used to refer to the 2004 and 2009 specifications, respectively. Full species names will be used, including specification version (for example, OWL2 EL). When referring more generally, ''OWL Family'' will be used.
History
Early ontology languages
There is a long history of
ontological
In metaphysics, ontology is the philosophical study of being, as well as related concepts such as existence, becoming, and reality.
Ontology addresses questions like how entities are grouped into categories and which of these entities exis ...
development in philosophy and computer science. Since the 1990s, a number of research efforts have explored how the idea of
knowledge representation
Knowledge representation and reasoning (KRR, KR&R, KR²) is the field of artificial intelligence (AI) dedicated to representing information about the world in a form that a computer system can use to solve complex tasks such as diagnosing a medic ...
(KR) from
artificial intelligence
Artificial intelligence (AI) is intelligence—perceiving, synthesizing, and inferring information—demonstrated by machines, as opposed to intelligence displayed by animals and humans. Example tasks in which this is done include speech re ...
(AI) could be made useful on the World Wide Web. These included languages based on
HTML
The HyperText Markup Language or HTML is the standard markup language for documents designed to be displayed in a web browser. It can be assisted by technologies such as Cascading Style Sheets (CSS) and scripting languages such as JavaScri ...
(called
SHOE
A shoe is an item of footwear intended to protect and comfort the human foot. They are often worn with a sock. Shoes are also used as an item of decoration and fashion. The design of shoes has varied enormously through time and from culture t ...
), based on XML (called XOL, later
OIL
An oil is any nonpolar chemical substance that is composed primarily of hydrocarbons and is hydrophobic (does not mix with water) & lipophilic (mixes with other oils). Oils are usually flammable and surface active. Most oils are unsaturated ...
), and various frame-based KR languages and knowledge acquisition approaches.
Ontology languages for the web
In 2000 in the United States,
DARPA
The Defense Advanced Research Projects Agency (DARPA) is a research and development agency of the United States Department of Defense responsible for the development of emerging technologies for use by the military.
Originally known as the Adv ...
started development of
DAML led by
James Hendler
James Alexander Hendler (born April 2, 1957) is an artificial intelligence researcher at Rensselaer Polytechnic Institute, United States, and one of the originators of the Semantic Web. He is a Fellow of the National Academy of Public Administr ...
.
In March 2001, the ''Joint EU/US Committee on Agent Markup Languages'' decided that DAML should be merged with OIL.
The ''EU/US ad hoc Joint Working Group on Agent Markup Languages'' was convened to develop
DAML+OIL as a web ontology language. This group was jointly funded by the DARPA (under the DAML program) and the European Union's
Information Society Technologies
The Framework Programmes for Research and Technological Development, also called Framework Programmes or abbreviated FP1 to FP9, are funding programmes created by the European Union/European Commission to support and foster research in the Europea ...
(IST) funding project. DAML+OIL was intended to be a thin layer above
RDFS
RDF Schema (Resource Description Framework Schema, variously abbreviated as RDFS, , RDF-S, or RDF/S) is a set of classes with certain properties using the RDF extensible knowledge representation data model, providing basic elements for the descr ...
,
with
formal semantics based on a
description logic (DL).
DAML+OIL is a particularly major influence on OWL; OWL's design was specifically based on DAML+OIL.
Semantic web standards
RDF schema
In the late 1990s, the World Wide Web Consortium (W3C) ''Metadata Activity'' started work on
RDF Schema
RDF Schema (Resource Description Framework Schema, variously abbreviated as RDFS, , RDF-S, or RDF/S) is a set of classes with certain properties using the RDF extensible knowledge representation data model, providing basic elements for the descr ...
(RDFS), a language for
RDF vocabulary sharing. The RDF became a W3C
Recommendation in February 1999, and RDFS a Candidate Recommendation in March 2000.
In February 2001, the ''Semantic Web Activity'' replaced the Metadata Activity.
In 2004 (as part of a wider revision of RDF) RDFS became a W3C Recommendation.
Though RDFS provides some support for ontology specification, the need for a more expressive ontology language had become clear.
Web-Ontology Working Group
The World Wide Web Consortium (W3C) created the ''Web-Ontology Working Group'' as part of their Semantic Web Activity. It began work on November 1, 2001 with co-chairs James Hendler and Guus Schreiber.
The first working drafts of the
abstract syntax
In computer science, the abstract syntax of data is its structure described as a data type (possibly, but not necessarily, an abstract data type), independent of any particular representation or encoding. This is particularly used in the representa ...
, reference and synopsis were published in July 2002.
OWL became a formal
W3C recommendation
The World Wide Web Consortium (W3C) is the main international standards organization for the World Wide Web. Founded in 1994 and led by Tim Berners-Lee, the consortium is made up of member organizations that maintain full-time staff working to ...
on February 10, 2004 and the working group was disbanded on May 31, 2004.
OWL Working Group
In 2005, at the ''OWL Experiences And Directions Workshop'' a consensus formed that recent advances in description logic would allow a more expressive revision to satisfy user requirements more comprehensively whilst retaining good computational properties.
In December 2006, the OWL1.1 Member Submission
was made to the W3C. The W3C chartered the ''OWL Working Group'' as part of the Semantic Web Activity in September 2007. In April 2008, this group decided to call this new language OWL2, indicating a substantial revision.
OWL 2 became a W3C recommendation in October 2009. OWL 2 introduces profiles to improve scalability in typical applications.
Acronym
OWL was chosen as an easily pronounced acronym that would yield good logos, suggest wisdom, and honor
William A. Martin
William Arthur Martin (1938-1981) was a computer scientist from Oklahoma City, Oklahoma, Oklahoma City, Oklahoma.
After graduating from Northwest Classen High School, where he was a state wrestling champion, he attended MIT where he received a ...
's ''One World Language'' knowledge representation project from the 1970s.
Adoption
A 2006 survey of ontologies available on the web collected 688 OWL ontologies. Of these, 199 were OWL Lite, 149 were OWL DL and 337 OWL Full (by syntax). They found that 19 ontologies had in excess of 2,000 classes, and that 6 had more than 10,000. The same survey collected 587 RDFS vocabularies.
In 2021 Prof.
Ian Horrocks
Ian Robert Horrocks One or more of the preceding sentences incorporates text from the royalsociety.org website where: is a professor of computer science at the University of Oxford in the UK and a Fellow of Oriel College, Oxford. His research ...
was awarded the
Lovelace Medal
The Lovelace Medal was established by the British Computer Society in 1998, and is presented to individuals who have made outstanding contributions to the understanding or advancement of computing. It is the top award in computing in the UK. Award ...
in recognition of his work towards the standardization of OWL which is considered the leading reason for its widespread adoption. The result of this research and development was RDFox, a
knowledge graph
The Google Knowledge Graph is a knowledge base from which Google serves relevant information in an infobox beside its search results. This allows the user to see the answer in a glance. The data is generated automatically from a variety of so ...
and
reasoning engine. The significance of this lies in the cultural shift of the technology space, leaving behind the dismissive attitude towards reasoning technology's inability to perform at speed, as RDFox proved beyond a doubt that high-speed reasoning was not only possible, but commercially viable. Many institutions have now adopted this technology as a solution to social and industrial problems involving highly interconnected data.
Ontologies
The data described by an ontology in the OWL family is interpreted as a set of "individuals" and a set of "property assertions" which relate these individuals to each other. An ontology consists of a set of
axiom
An axiom, postulate, or assumption is a statement that is taken to be true, to serve as a premise or starting point for further reasoning and arguments. The word comes from the Ancient Greek word (), meaning 'that which is thought worthy or f ...
s which place constraints on sets of individuals (called "classes") and the types of relationships permitted between them. These axioms provide semantics by allowing systems to infer additional information based on the data explicitly provided. A full introduction to the expressive power of the OWL is provided in the W3C's ''OWL Guide''.
OWL ontologies can import other ontologies, adding information from the imported ontology to the current ontology.
Example
An ontology describing families might include axioms stating that a "hasMother" property is only present between two individuals when "hasParent" is also present, and that individuals of class "HasTypeOBlood" are never related via "hasParent" to members of the "HasTypeABBlood" class. If it is stated that the individual Harriet is related via "hasMother" to the individual Sue, and that Harriet is a member of the "HasTypeOBlood" class, then it can be inferred that Sue is not a member of "HasTypeABBlood". This is, however, only true if the concepts of "Parent" and "Mother" only mean biological parent or mother and not social parent or mother.
Species
OWL dialects
The W3C-endorsed OWL specification includes the definition of three variants of OWL, with different levels of expressiveness. These are OWL Lite, OWL DL and OWL Full (ordered by increasing expressiveness). Each of these
sublanguage
A sublanguage is a subset of a language. Sublanguages occur in natural language, computer programming language, and relational databases.
In natural language
In informatics, natural language processing, and machine translation, a sublanguage is ...
s is a syntactic extension of its simpler predecessor. The following set of relations hold. Their inverses do not.
* Every legal OWL Lite ontology is a legal OWL DL ontology.
* Every legal OWL DL ontology is a legal OWL Full ontology.
* Every valid OWL Lite conclusion is a valid OWL DL conclusion.
* Every valid OWL DL conclusion is a valid OWL Full conclusion.
OWL Lite
OWL Lite was originally intended to support those users primarily needing a classification hierarchy and simple constraints. For example, while it supports
cardinality
In mathematics, the cardinality of a set is a measure of the number of elements of the set. For example, the set A = \ contains 3 elements, and therefore A has a cardinality of 3. Beginning in the late 19th century, this concept was generalized ...
constraints, it only permits cardinality values of 0 or 1. It was hoped that it would be simpler to provide tool support for OWL Lite than its more expressive relatives, allowing quick migration path for systems using
thesauri
A thesaurus (plural ''thesauri'' or ''thesauruses'') or synonym dictionary is a reference work for finding synonyms and sometimes antonyms of words. They are often used by writers to help find the best word to express an idea:
Synonym dictionar ...
and other
taxonomies. In practice, however, most of the expressiveness constraints placed on OWL Lite amount to little more than syntactic inconveniences: most of the constructs available in OWL DL can be built using complex combinations of OWL Lite features, and is equally expressive as the description logic
.
Development of OWL Lite tools has thus proven to be almost as difficult as development of tools for OWL DL, and OWL Lite is not widely used.
OWL DL
OWL DL is designed to provide the maximum expressiveness possible while retaining computational
completeness (either φ or ¬φ holds),
decidability (there is an effective procedure to determine whether φ is derivable or not), and the availability of practical reasoning algorithms. OWL DL includes all OWL language constructs, but they can be used only under certain restrictions (for example, number restrictions may not be placed upon properties which are declared to be transitive; and while a class may be a subclass of many classes, a class cannot be an instance of another class). OWL DL is so named due to its correspondence with
description logic, a field of research that has studied the logics that form the formal foundation of OWL.
OWL Full
OWL Full is based on a different semantics from OWL Lite or OWL DL, and was designed to preserve some compatibility with RDF Schema. For example, in OWL Full a class can be treated simultaneously as a collection of individuals and as an individual in its own right; this is not permitted in OWL DL. OWL Full allows an ontology to augment the meaning of the pre-defined (RDF or OWL) vocabulary. OWL Full is undecidable, so no reasoning software is able to perform complete reasoning for it.
OWL2 profiles
In OWL 2, there are three sublanguages of the language. OWL 2 EL is a fragment that has polynomial time reasoning complexity; OWL 2 QL is designed to enable easier access and query to data stored in databases; OWL 2 RL is a rule subset of OWL 2.
Syntax
The OWL family of languages supports a variety of syntaxes. It is useful to distinguish ''high level'' syntaxes aimed at specification from ''exchange'' syntaxes more suitable for general use.
High level
These are close to the ontology structure of languages in the OWL family.
OWL abstract syntax
High level syntax is used to specify the OWL ontology structure and semantics.
The OWL abstract syntax presents an ontology as a sequence of ''annotations'', ''axioms'' and ''facts''. Annotations carry machine and human oriented meta-data. Information about the classes, properties and individuals that compose the ontology is contained in axioms and facts only.
Each class, property and individual is either ''anonymous'' or identified by an
URI reference. Facts state data either about an individual or about a pair of individual identifiers (that the objects identified are distinct or the same). Axioms specify the characteristics of classes and properties. This style is similar to
frame language Frames are an artificial intelligence data structure used to divide knowledge into substructures by representing " stereotyped situations". They were proposed by Marvin Minsky in his 1974 article "A Framework for Representing Knowledge". Frames are ...
s, and quite dissimilar to well known syntaxes for
DLs and
Resource Description Framework The Resource Description Framework (RDF) is a World Wide Web Consortium (W3C) standard originally designed as a data model for metadata. It has come to be used as a general method for description and exchange of graph data. RDF provides a variety of ...
(RDF).
Sean Bechhofer, ''et al.'' argue that though this syntax is hard to parse, it is quite concrete. They conclude that the name ''abstract syntax'' may be somewhat misleading.
OWL2 functional syntax
This syntax closely follows the structure of an OWL2 ontology. It is used by OWL2 to specify semantics, mappings to exchange syntaxes and profiles.
Exchange syntaxes
RDF syntaxes
Syntactic mappings into
RDF are specified
for languages in the OWL family. Several RDF
serialization formats have been devised. Each leads to a syntax for languages in the OWL family through this mapping. RDF/XML is normative.
OWL2 XML syntax
OWL2 specifies an
XML
Extensible Markup Language (XML) is a markup language and file format for storing, transmitting, and reconstructing arbitrary data. It defines a set of rules for encoding documents in a format that is both human-readable and machine-readable ...
serialization that closely models the structure of an OWL2 ontology.
Manchester Syntax
The Manchester Syntax is a compact, human readable syntax with a style close to frame languages.
Variations are available for OWL and OWL2. Not all OWL and OWL2 ontologies can be expressed in this syntax.
Examples
* The W3C OWL 2 Web Ontology Language provides syntax examples.
Tea ontology
Consider an ontology for tea based on a Tea class. First, an ontology identifier is needed. Every OWL ontology must be identified by a
URI Uri may refer to:
Places
* Canton of Uri, a canton in Switzerland
* Úri, a village and commune in Hungary
* Uri, Iran, a village in East Azerbaijan Province
* Uri, Jammu and Kashmir, a town in India
* Uri (island), an island off Malakula Islan ...
(
http://www.example.org/tea.owl, say). This example provides a sense of the syntax. To save space below, preambles and prefix definitions have been skipped.
;OWL2 Functional Syntax:
Ontology(
Declaration( Class( :Tea ) )
)
;OWL2 XML Syntax:
;Manchester Syntax:
Ontology:
Class: Tea
;RDF/XML syntax:
;RDF/
Turtle
Turtles are an order of reptiles known as Testudines, characterized by a special shell developed mainly from their ribs. Modern turtles are divided into two major groups, the Pleurodira (side necked turtles) and Cryptodira (hidden necked tu ...
:
rdf:type owl:Ontology .
:Tea rdf:type owl:Class .
Semantics
Relation to description logics
OWL classes correspond to
description logic (DL) ''concepts'', OWL properties to DL ''roles'', while ''individuals'' are called the same way in both the OWL and the DL terminology.
Early attempts to build large ontologies were plagued by a lack of clear definitions. Members of the OWL family have
model theoretic
In mathematical logic, model theory is the study of the relationship between formal theories (a collection of sentences in a formal language expressing statements about a mathematical structure), and their models (those structures in which the st ...
formal semantics, and so have strong
logic
Logic is the study of correct reasoning. It includes both formal and informal logic. Formal logic is the science of deductively valid inferences or of logical truths. It is a formal science investigating how conclusions follow from premises ...
al foundations.
Description logics are a family of logics that are decidable fragments of
first-order logic
First-order logic—also known as predicate logic, quantificational logic, and first-order predicate calculus—is a collection of formal systems used in mathematics, philosophy, linguistics, and computer science. First-order logic uses quantifie ...
with attractive and well-understood computational properties. OWL DL and OWL Lite semantics are based on DLs.
They combine a syntax for describing and exchanging ontologies, and formal semantics that gives them meaning. For example, OWL DL corresponds to the
description logic, while OWL 2 corresponds to the
logic. Sound, complete, terminating
reasoners (i.e. systems which are guaranteed to derive every consequence of the knowledge in an ontology) exist for these DLs.
Relation to RDFS
OWL Full is intended to be compatible with
RDF Schema
RDF Schema (Resource Description Framework Schema, variously abbreviated as RDFS, , RDF-S, or RDF/S) is a set of classes with certain properties using the RDF extensible knowledge representation data model, providing basic elements for the descr ...
(RDFS), and to be capable of augmenting the meanings of existing
Resource Description Framework The Resource Description Framework (RDF) is a World Wide Web Consortium (W3C) standard originally designed as a data model for metadata. It has come to be used as a general method for description and exchange of graph data. RDF provides a variety of ...
(RDF) vocabulary. A
model theory
In mathematical logic, model theory is the study of the relationship between formal theories (a collection of sentences in a formal language expressing statements about a mathematical structure), and their models (those structures in which the s ...
describes the formal semantics for
RDF. This interpretation provides the meaning of RDF and RDFS vocabulary. So, the meaning of OWL Full ontologies are defined by extension of the RDFS meaning, and OWL Full is a
semantic extension of RDF.
Open world assumption
The languages in the OWL family use the
open world assumption
In a formal system of logic used for knowledge representation, the open-world assumption is the assumption that the truth value of a statement may be true irrespective of whether or not it is ''known'' to be true. It is the opposite of the clos ...
. Under the open world assumption, if a statement cannot be proven to be true with current knowledge, we cannot draw the conclusion that the statement is false.
Contrast to other languages
A
relational database
A relational database is a (most commonly digital) database based on the relational model of data, as proposed by E. F. Codd in 1970. A system used to maintain relational databases is a relational database management system (RDBMS). Many relatio ...
consists of sets of
tuple
In mathematics, a tuple is a finite ordered list (sequence) of elements. An -tuple is a sequence (or ordered list) of elements, where is a non-negative integer. There is only one 0-tuple, referred to as ''the empty tuple''. An -tuple is defi ...
s with the same
attribute
Attribute may refer to:
* Attribute (philosophy), an extrinsic property of an object
* Attribute (research), a characteristic of an object
* Grammatical modifier, in natural languages
* Attribute (computing), a specification that defines a prope ...
s.
SQL is a query and management language for relational databases.
Prolog
Prolog is a logic programming language associated with artificial intelligence and computational linguistics.
Prolog has its roots in first-order logic, a formal logic, and unlike many other programming languages, Prolog is intended primarily ...
is a
logical programming
Logic programming is a programming paradigm which is largely based on formal logic. Any program written in a logic programming language is a set of sentences in logical form, expressing facts and rules about some problem domain. Major logic prog ...
language. Both use the
closed world assumption The closed-world assumption (CWA), in a formal system of logic used for knowledge representation, is the presumption that a statement that is true is also known to be true. Therefore, conversely, what is not currently known to be true, is false. Th ...
.
Terminology
Languages in the OWL family are capable of creating classes, properties, defining instances and its operations.
Instances
An ''instance'' is an object. It corresponds to a description logic ''individual''.
Classes
A ''class'' is a collection of objects. A
class
Class or The Class may refer to:
Common uses not otherwise categorized
* Class (biology), a taxonomic rank
* Class (knowledge representation), a collection of individuals or objects
* Class (philosophy), an analytical concept used differentl ...
may contain individuals, ''instances'' of the class. A class may have any number of instances. An instance may belong to none, one or more classes.
A class may be a ''subclass'' of another, inheriting characteristics from its parent ''superclass''. This corresponds to
logical
Logic is the study of correct reasoning. It includes both formal and informal logic. Formal logic is the science of deductively valid inferences or of logical truths. It is a formal science investigating how conclusions follow from premises ...
subsumption
Subsumption may refer to:
* A minor premise in symbolic logic (see syllogism)
* The Liskov substitution principle in object-oriented programming
* Subtyping in programming language theory
* Subsumption architecture in robotics
* A subsumption ...
and DL ''concept inclusion'' notated
.
All classes are subclasses of owl:Thing (DL ''
top
A spinning top, or simply a top, is a toy with a squat body and a sharp point at the bottom, designed to be spun on its vertical axis, balancing on the tip due to the gyroscopic effect.
Once set in motion, a top will usually wobble for a few ...
'' notated
), the ''root'' class.
All classes are subclassed by owl:Nothing (DL ''
bottom
Bottom may refer to:
Anatomy and sex
* Bottom (BDSM), the partner in a BDSM who takes the passive, receiving, or obedient role, to that of the top or dominant
* Bottom (sex), a term used by gay couples and BDSM
* Buttocks or bottom, part of th ...
'' notated
), the ''empty'' class. No instances are members of owl:Nothing. Modelers use owl:Thing and owl:Nothing to assert facts about all or no instances.
Class and their members can be defined in OWL either by
extension
Extension, extend or extended may refer to:
Mathematics
Logic or set theory
* Axiom of extensionality
* Extensible cardinal
* Extension (model theory)
* Extension (predicate logic), the set of tuples of values that satisfy the predicate
* E ...
or by
intension
In any of several fields of study that treat the use of signs — for example, in linguistics, logic, mathematics, semantics, semiotics, and philosophy of language — an intension is any property or quality connoted by a word, phrase, or anoth ...
. An individual can be explicitly assigned a class by a ''Class assertion'', for example we can add a statement ''
Queen elizabeth is a(n instance of)
human'', or by a class expression with ClassExpression statements ''every instance of the
human class who has a
female value to the
sex property is an instance of the
woman class''.
Example
Let's call
human the class of all humans in the world is a subclass of owl:thing. The class of all women (say
woman) in the world is a subclass of
human.
Then we have
The membership of some individual to a class could be noted
ClassAssertion(
human George_Washington )
and class inclusion
SubClassOf(
woman human )
The first means "George Washington is a human" and the second "every woman is human".
Properties
A property is a characteristic of a class - a directed binary relation that specifies some attribute which is true for instances of that class. Properties sometimes act as data values, or links to other instances. Properties may exhibit logical features, for example, by being transitive, symmetric, inverse and functional. Properties may also have domains and ranges.
Datatype properties
Datatype properties are relations between instances of classes and RDF literals or XML schema datatypes. For example, modelName (String datatype) is the property of Manufacturer class. They are formulated using ''owl:DatatypeProperty'' type.
Object properties
Object properties are relations between instances of two classes. For example,
ownedBy
may be an object type property of the Vehicle class and may have a range which is the class Person. They are formulated using ''owl:ObjectProperty''.
Operators
Languages in the OWL family support various operations on classes such as
union
Union commonly refers to:
* Trade union, an organization of workers
* Union (set theory), in mathematics, a fundamental operation on sets
Union may also refer to:
Arts and entertainment
Music
* Union (band), an American rock group
** ''Un ...
,
intersection and
complement
A complement is something that completes something else.
Complement may refer specifically to:
The arts
* Complement (music), an interval that, when added to another, spans an octave
** Aggregate complementation, the separation of pitch-clas ...
. They also allow class enumeration,
cardinality
In mathematics, the cardinality of a set is a measure of the number of elements of the set. For example, the set A = \ contains 3 elements, and therefore A has a cardinality of 3. Beginning in the late 19th century, this concept was generalized ...
,
disjointness
In mathematics, two sets are said to be disjoint sets if they have no element in common. Equivalently, two disjoint sets are sets whose intersection is the empty set.. For example, and are ''disjoint sets,'' while and are not disjoint. A c ...
, and
equivalence.
Metaclasses
Metaclass
In object-oriented programming, a metaclass is a class whose instances are classes. Just as an ordinary class defines the behavior of certain objects, a metaclass defines the behavior of certain classes and their instances. Not all object-oriente ...
es are
classes of classes. They are allowed in OWL full or with a feature called class/instance punning.
Public ontologies
Libraries
Biomedical
*
OBO Foundry
The Open Biological and Biomedical Ontologies (OBO) Foundry is a group of people dedicated to build and maintain ontologies related to the life sciences. The OBO Foundry establishes a set of principles for ontology development for creating a su ...
*
NCBO BioPortal
*
NCI Enterprise Vocabulary Services
Standards
*
Suggested Upper Merged Ontology
The Suggested Upper Merged Ontology (SUMO) is an upper ontology intended as a foundation ontology for a variety of computer information processing systems. SUMO defines a hierarchy of ''classes'' and related rules and relationships. These are expr ...
(SUMO)
*
TDWG
* PROV-O, the ontology version of the
W3C's PROV-DM
*
Basic Formal Ontology
Basic Formal Ontology (BFO) is a top-level ontology developed by Barry Smith and his associates for the purposes of promoting interoperability among domain ontologies built in its terms through a process of downward population. A guide to buil ...
(BFO)
*
European Materials Modelling Ontology
European, or Europeans, or Europeneans, may refer to:
In general
* ''European'', an adjective referring to something of, from, or related to Europe
** Ethnic groups in Europe
** Demographics of Europe
** European cuisine, the cuisines of Europe a ...
(EMMO)
Browsers
The following tools include public ontology browsers:
*
Protégé OWL
Search
*
Swoogle Swoogle was a search engine for Semantic Web ontologies, documents, terms and data published on the Web. Swoogle employed a system of crawlers to discover RDF documents and HTML documents with embedded RDF content. Swoogle reasoned about these d ...
Limitations
* No direct language support for n-ary relationships. For example, modelers may wish to describe the qualities of a relation, to relate more than 2 individuals or to relate an individual to a list. This cannot be done within OWL. They may need to adopt a pattern instead which encodes the meaning outside the formal semantics.
See also
*
RDF
*
Semantic technology
The ultimate goal of semantic technology is to help machines understand data. To enable the encoding of semantics with the data, well-known technologies are RDF (Resource Description Framework) and OWL (Web Ontology Language). These technologies ...
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Agris: International Information System for the Agricultural Sciences and Technology
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Common Logic
Common Logic (CL) is a framework for a family of logic languages, based on first-order logic, intended to facilitate the exchange and transmission of knowledge in computer-based systems.
The CL definition permits and encourages the development o ...
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FOAF
FOAF (an acronym of friend of a friend) is a machine-readable ontology describing persons, their activities and their relations to other people and objects. Anyone can use FOAF to describe themselves. FOAF allows groups of people to describe soc ...
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DOAC
Anticoagulants, commonly known as blood thinners, are chemical substances that prevent or reduce coagulation of blood, prolonging the clotting time. Some of them occur naturally in blood-eating animals such as leeches and mosquitoes, where the ...
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Frame language Frames are an artificial intelligence data structure used to divide knowledge into substructures by representing " stereotyped situations". They were proposed by Marvin Minsky in his 1974 article "A Framework for Representing Knowledge". Frames are ...
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Geopolitical ontology
The FAO geopolitical ontology is an ontology developed by the Food and Agriculture Organization of the United Nations (FAO) to describe, manage and exchange data related to geopolitical entities such as countries, territories, regions and other si ...
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IDEAS Group
The IDEAS Group is the International Defence Enterprise Architecture Specification for exchange Group. The deliverable of the project is a data exchange format for military Enterprise Architectures. The scope is four nation (plus NATO as observer ...
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Meta-Object Facility (MOF), a different standard for the
Unified Modeling Language (UML) of the
Object Management Group (OMG)
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Metaclass (Semantic Web), a featured allowed by OWL to represent knowledge
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Multimedia Web Ontology Language
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Semantic reasoner
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SKOS
Simple Knowledge Organization System (SKOS) is a W3C recommendation designed for representation of thesauri, classification schemes, taxonomies, subject-heading systems, or any other type of structured controlled vocabulary. SKOS is part of the ...
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SSWAP: Simple Semantic Web Architecture and Protocol
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SHACL
Shapes Constraint Language (SHACL) is a World Wide Web Consortium (W3C) standard language for describing Resource Description Framework (RDF) graphs. SHACL has been designed to enhance the semantic and technical interoperability layers of ontolog ...
: Shapes and Constraints Language for RDF
References
Further reading
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{{Authority control
World Wide Web Consortium standards
Resource Description Framework
XML-based standards
Declarative programming languages
Ontology languages
Semantic Web