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The Resource Description Framework (RDF) is a
World Wide Web Consortium The World Wide Web Consortium (W3C) is the main international standards organization A standards organization, standards body, standards developing organization (SDO), or standards setting organization (SSO) is an organization whose primary ...
(W3C) standard originally designed as a
data model A data model (or datamodel) is an abstract model A conceptual model is a representation of a system, made of the composition of concept Concepts are defined as abstract ideas or general notions that occur in the mind, in speech, or in thought. ...

data model
for
metadata Metadata is "data Data (; ) are individual facts, statistics, or items of information, often numeric. In a more technical sense, data are a set of values of qualitative property, qualitative or quantity, quantitative variable (research), v ...

metadata
. It has come to be used as a general method for description and exchange of graph data. RDF provides a variety of
syntax In linguistics Linguistics is the scientific study of language, meaning that it is a comprehensive, systematic, objective, and precise study of language. Linguistics encompasses the analysis of every aspect of language, as well as the ...

syntax
notations and
data serialization In computing, serialization (US spelling) or serialisation (UK spelling) is the process of translating a data structure or object (computer science), object state into a format that can be stored (for example, in a computer file, file or memory d ...
formats with
Turtle Turtles are an order Order, ORDER or Orders may refer to: * Orderliness Orderliness is a quality that is characterized by a person’s interest in keeping their surroundings and themselves well organized, and is associated with other qu ...
(Terse RDF Triple Language) currently being the most widely used notation. RDF is a directed graph composed of triple statements. An RDF graph statement is represented by: 1) a node for the subject, 2) an arc that goes from a subject to an object for the predicate and 3) a node for the object. Each of the three parts of the statement can be identified by a URI. An object can also be a literal value. This simple, flexible data model has a lot of expressive power to represent complex situations, relationships, and other things of interest, while also being appropriately abstract. RDF was adopted as a W3C recommendation in 1999. The RDF 1.0 specification was published in 2004, the RDF 1.1 specification in 2014.
SPARQL SPARQL (pronounced " sparkle" , a recursive acronym A recursive acronym is an acronym An acronym is a word or name formed from the initial components of a longer name or phrase, usually using individual initial letters, as in NATO (North ...
is a standard query language for RDF graphs.
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 Knowledge representation and reasoning (KRR, KR& ...
,
OWL Owls are bird Birds are a group of warm-blooded vertebrate Vertebrates () comprise all species of animal Animals (also called Metazoa) are multicellular eukaryotic organisms that form the Kingdom (biology), biological k ...
and
SHACL Shapes Constraint Language (SHACL) is a World Wide Web Consortium The World Wide Web Consortium (W3C) is the main international standards organization A standards organization, standards body, standards developing organization (SDO), or ...
are
ontology language In computer science and artificial intelligence, ontology languages are formal languages used to construct ontology (information science), ontologies. They allow the encoding of knowledge about specific Field of study, domains and often include re ...
s that are used to describe RDF data.


Overview

The RDF data model is similar to classical conceptual modeling approaches (such as entity–relationship or
class diagram In software engineering Software engineering is the systematic application of engineering Engineering is the use of scientific principles to design and build machines, structures, and other items, including bridges, tunnels, roads, vehic ...

class diagram
s). It is based on the idea of making
statement Statement or statements may refer to: Common uses *Statement (computer science), the smallest standalone element of an imperative programming language *Statement (logic), declarative sentence that is either true or false *Statement, a Sentence_(lin ...
s about
resource Resource refers to all the materials available in our environment which help us to satisfy our needs and wants. Resources can broadly be classified upon their availability — they are classified into renewable A renewable resource, also know ...
s (in particular web resources) in expressions of the form subjectpredicateobject, known as ''
triples Triple is used in several contexts to mean "threefold" or a "Treble (disambiguation), treble": Sports * Triple (baseball), a three-base hit * A basketball three-point field goal * A figure skating jump with three rotations * In bowling terms, thre ...
''. The subject denotes the resource, and the predicate denotes traits or aspects of the resource, and expresses a relationship between the subject and the object. For example, one way to represent the notion "The sky has the color blue" in RDF is as the triple: a
subject Subject ( la, subiectus "lying beneath") may refer to: Philosophy *''Hypokeimenon ''Hypokeimenon'' (Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the He ...
denoting "the sky", a
predicate Predicate or predication may refer to: Computer science *Syntactic predicate (in parser technology) guidelines the parser process Linguistics *Predicate (grammar), a grammatical component of a sentence Philosophy and logic * Predication (philo ...
denoting "has the color", and an
object Object may refer to: General meanings * Object (philosophy) An object is a philosophy, philosophical term often used in contrast to the term ''Subject (philosophy), subject''. A subject is an observer and an object is a thing observed. For mo ...
denoting "blue". Therefore, RDF uses subject instead of object (or entity) in contrast to the typical approach of an
entity–attribute–value model Entity–attribute–value model (EAV) is a data model to encode, in a space-efficient manner, entities where the number of attributes (properties, parameters) that can be used to describe them is potentially vast, but the number that will actually ...
in
object-oriented design Object-oriented design is the process of planning a system of interacting objects for the purpose of solving a software problem. It is one approach to software design Software design is the process by which an Agency (philosophy), agent creat ...
: entity (sky), attribute (color), and value (blue). RDF is an abstract model with several
serialization formats
serialization formats
(being essentially specialized
file format A file format is a standard Standard may refer to: Flags * Colours, standards and guidons * Standard (flag), a type of flag used for personal identification Norm, convention or requirement * Standard (metrology), an object that bears ...
s), in addition the particular encoding for resources or triples can vary from format to format. This mechanism for describing resources is a major
component Component may refer to: In engineering, science, and technology Generic systems *System components, an entity with discrete structure, such as an assembly or software module, within a system considered at a particular level of analysis *Lumped ele ...
in the W3C's
Semantic Web The Semantic Web (sometimes known as Web 3.0) is an extension of the World Wide Web The World Wide Web (WWW), commonly known as the Web, is an information system An information system (IS) is a formal, sociotechnical Sociotechnica ...

Semantic Web
activity: an evolutionary stage of the
World Wide Web The World Wide Web (WWW), commonly known as the Web, is an information system An information system (IS) is a formal, sociotechnical Sociotechnical systems (STS) in organizational development is an approach to complex organizational ...
in which automated software can store, exchange, and use machine-readable information distributed throughout the Web, in turn enabling users to deal with the information with greater efficiency and
certainty Certainty (also known as epistemic certainty or objective certainty) is the property of s which a person has no rational grounds for doubting. One standard way of defining epistemic certainty is that a belief is certain if and only if the per ...
. RDF's simple data model and ability to model disparate, abstract concepts has also led to its increasing use in
knowledge management Knowledge management (KM) is the collection of methods relating to creating, sharing, using and managing the knowledge Knowledge is a familiarity or awareness, of someone or something, such as facts A fact is something that is truth, ...

knowledge management
applications unrelated to Semantic Web activity. A collection of RDF statements intrinsically represents a
labeled
labeled
,
directed Director may refer to: Literature * Director (magazine), ''Director'' (magazine), a British magazine * The Director (novel), ''The Director'' (novel), a 1971 novel by Henry Denker * The Director (play), ''The Director'' (play), a 2000 play by Nan ...

directed
multi-graph
multi-graph
. This makes an RDF
data model A data model (or datamodel) is an abstract model A conceptual model is a representation of a system, made of the composition of concept Concepts are defined as abstract ideas or general notions that occur in the mind, in speech, or in thought. ...

data model
better suited to certain kinds of
knowledge representation Knowledge representation and reasoning (KRR, KR&R, KR²) is the field of artificial intelligence Artificial intelligence (AI) is intelligence Intelligence has been defined in many ways: the capacity for abstraction Abstraction in its ...
than are other relational or
ontological Ontology is the branch of philosophy Philosophy (from , ) is the study of general and fundamental questions, such as those about reason, Metaphysics, existence, Epistemology, knowledge, Ethics, values, Philosophy of mind, mind, and Ph ...
models. As
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 Knowledge representation and reasoning (KRR, KR& ...
,
OWL Owls are bird Birds are a group of warm-blooded vertebrate Vertebrates () comprise all species of animal Animals (also called Metazoa) are multicellular eukaryotic organisms that form the Kingdom (biology), biological k ...
and
SHACL Shapes Constraint Language (SHACL) is a World Wide Web Consortium The World Wide Web Consortium (W3C) is the main international standards organization A standards organization, standards body, standards developing organization (SDO), or ...
demonstrate, one can build additional
ontology language In computer science and artificial intelligence, ontology languages are formal languages used to construct ontology (information science), ontologies. They allow the encoding of knowledge about specific Field of study, domains and often include re ...
s upon RDF.


History

The initial RDF design, intended to "build a vendor-neutral and operating system-independent system of metadata," derived from the W3C's
Platform for Internet Content Selection The Platform for Internet Content Selection (PICS) was a specification created by W3C that used Metadata (computing), metadata to label webpages to help parents and teachers control what children and students could access on the Internet. The W3C Pr ...
(PICS), an early web content labelling system, but the project was also shaped by ideas from
Dublin Core 220px, Logo image of DCMI, which formulates Dublin Core The Dublin Core, also known as the Dublin Core Metadata Element Set, is a set of fifteen "core" elements (properties) for describing resources. This fifteen-element Dublin Core has been for ...
, and from the
Meta Content Framework Meta Content Framework (MCF) is a specification of a content format A content format is an encoded In communication Communication (from Latin ''communicare'', meaning "to share" or "to be in relation with") is "an apparent answer to the p ...
(MCF), which had been developed during 1995–1997 by Ramanathan V. Guha at
Apple An apple is an edible fruit In botany Botany, also called , plant biology or phytology, is the science of plant life and a branch of biology. A botanist, plant scientist or phytologist is a scientist who specialises in this fie ...
and
Tim Bray Timothy William Bray (born June 21, 1955) is a Canadian Canadians (french: Canadiens) are people identified with the country of Canada Canada is a country in the northern part of North America. Its Provinces and territories of Can ...

Tim Bray
at
Netscape Netscape Communications Corporation (originally Mosaic Communications Corporation) was an American independent computer services company with headquarters in Mountain View, California Mountain View is a city in Santa Clara County, Californi ...
. A first public draft of RDF appeared in October 1997, issued by a W3C working group that included representatives from
IBM International Business Machines Corporation (IBM) is an American multinational technology company headquartered in Armonk, New York, with operations in over 170 countries. The company began in 1911, founded in Endicott, New York, as the C ...

IBM
,
Microsoft Microsoft Corporation is an American multinational corporation, multinational technology company, technology corporation which produces Software, computer software, consumer electronics, personal computers, and related services. Its best-know ...

Microsoft
,
Netscape Netscape Communications Corporation (originally Mosaic Communications Corporation) was an American independent computer services company with headquarters in Mountain View, California Mountain View is a city in Santa Clara County, Californi ...

Netscape
,
Nokia Nokia Corporation (natively Nokia Oyj, referred to as Nokia; stylized as NOKIA) is a Finnish multinational Multinational may refer to: * Multinational corporation, a corporate organization operating in multiple countries * Multinational for ...

Nokia
,
Reuters Reuters (, ) is an international news organisation owned by Thomson Reuters. It employs around 2,500 journalists and 600 photojournalists in about 200 locations worldwide. Reuters is one of the largest news agencies in the world. The agency w ...
,
SoftQuadSoftQuad Software was a Canadian software company best known for HoTMetaL, the first commercial HTML editor. It is also known for Author/Editor, the first specialized SGML editor, and Panorama, the first browser plugin for SGML. Panorama demonstrated ...
, and the
University of Michigan , mottoeng = "Arts, Knowledge, Truth" , former_names = Catholepistemiad, or University of Michigania (1817–1821) , budget = $8.99 billion (2018) , endowment = $17 billion (2021)As of October 25, 2021. ...

University of Michigan
. In 1999, the W3C published the first recommended RDF specification, the ''Model and Syntax Specification'' ("RDF M&S"). This described RDF's data model and an
XML Extensible Markup Language (XML) is a markup language #REDIRECT Markup language In computer text processing, a markup language is a system for annotation, annotating a document in a way that is Syntax (logic), syntactically distinguishable fro ...

XML
serialization. Two persistent misunderstandings about RDF developed at this time: firstly, due to the MCF influence and the RDF "Resource Description" initialism, the idea that RDF was specifically for use in representing metadata; secondly that RDF was an XML format rather than a data model, and only the RDF/XML serialisation being XML-based. RDF saw little take-up in this period, but there was significant work done in
Bristol Bristol () is a city A city is a large human settlement.Goodall, B. (1987) ''The Penguin Dictionary of Human Geography''. London: Penguin.Kuper, A. and Kuper, J., eds (1996) ''The Social Science Encyclopedia''. 2nd edition. London: Routle ...

Bristol
, around ILRT at
Bristol University The University of Bristol is a Red brick university, red brick Russell Group research university in Bristol, England. It received its royal charter in 1909, although it can trace its roots to a Society of Merchant Venturers, Merchant Venturers' sc ...
and
HP Labs HP Labs is the exploratory and advanced research group for HP Inc. HP Inc. is an American multinational information Information can be thought of as the resolution of uncertainty; it answers the question of "What an entity is" and ...
, and in Boston at
MIT Massachusetts Institute of Technology (MIT) is a private land-grant research university A research university is a university A university ( la, universitas, 'a whole') is an educational institution, institution of higher education, hi ...

MIT
. RSS 1.0 and FOAF became exemplar applications for RDF in this period. The recommendation of 1999 was replaced in 2004 by a set of six specifications: "The RDF Primer", "RDF Concepts and Abstract", "RDF/XML Syntax Specification (revised)", "RDF Semantics", "RDF Vocabulary Description Language 1.0", and "The RDF Test Cases". This series was superseded in 2014 by the following six "RDF 1.1" documents: "RDF 1.1 Primer," "RDF 1.1 Concepts and Abstract Syntax," "RDF 1.1 XML Syntax," "RDF 1.1 Semantics," "RDF Schema 1.1," and "RDF 1.1 Test Cases".


RDF topics


Vocabulary

The vocabulary defined by the RDF specification is as follows:


Classes


= rdf

= * rdf:XMLLiteral – the class of XML literal values * rdf:Property – the class of properties * rdf:Statement – the class of RDF statements * rdf:Alt, rdf:Bag, rdf:Seq – containers of alternatives, unordered containers, and ordered containers (rdfs:Container is a super-class of the three) * rdf:List – the class of RDF Lists * rdf:nil – an instance of rdf:List representing the empty list


= rdfs

= * rdfs:Resource – the class resource, everything * rdfs:Literal – the class of literal values, e.g.
string String or strings may refer to: *String (structure), a long flexible structure made from threads twisted together, which is used to tie, bind, or hang other objects Arts, entertainment, and media Films * Strings (1991 film), ''Strings'' (1991 fil ...
s and
integer An integer (from the Latin Latin (, or , ) is a classical language A classical language is a language A language is a structured system of communication Communication (from Latin ''communicare'', meaning "to share" or "to ...
s * rdfs:Class – the class of classes * rdfs:Datatype – the class of RDF datatypes * rdfs:Container – the class of RDF containers * rdfs:ContainerMembershipProperty – the class of container membership properties, rdf:_1, rdf:_2, ..., all of which are sub-properties of rdfs:member


Properties


=rdf

= * rdf:type – an instance of rdf:Property used to state that a resource is an instance of a class * rdf:first – the first item in the subject RDF list * rdf:rest – the rest of the subject RDF list after rdf:first * rdf:value – idiomatic property used for structured values * rdf:subject – the subject of the RDF statement * rdf:predicate – the predicate of the RDF statement * rdf:object – the object of the RDF statement rdf:Statement, rdf:subject, rdf:predicate, rdf:object are used for
reification Reification may refer to: Science and technology * Reification (computer science), the creation of a data model * Reification (knowledge representation), the representation of facts and/or assertions * Reification (statistics), the use of an ideali ...
(see
below Below may refer to: *Earth *Ground (disambiguation) *Soil *Floor *Bottom (disambiguation) *Less than *Temperatures below freezing *Hell or underworld People with the surname *Fred Below (1926–1988), American blues drummer *Fritz von Below (1853 ...
).


=rdfs

= * rdfs:subClassOf – the subject is a subclass of a class * rdfs:subPropertyOf – the subject is a subproperty of a property * rdfs:domain – a domain of the subject property * rdfs:range – a range of the subject property * rdfs:label – a human-readable name for the subject * rdfs:comment – a description of the subject resource * rdfs:member – a member of the subject resource * rdfs:seeAlso – further information about the subject resource * rdfs:isDefinedBy – the definition of the subject resource This vocabulary is used as a foundation for RDF Schema, where it is extended.


Serialization formats

Several common are in use, including: *
Turtle Turtles are an order Order, ORDER or Orders may refer to: * Orderliness Orderliness is a quality that is characterized by a person’s interest in keeping their surroundings and themselves well organized, and is associated with other qu ...
, a compact, human-friendly format. * N-Triples, a very simple, easy-to-parse, line-based format that is not as compact as Turtle. * N-Quads, a superset of N-Triples, for serializing multiple RDF graphs. * JSON-LD, a JSON-based serialization. * N3 or Notation3, a non-standard serialization that is very similar to Turtle, but has some additional features, such as the ability to define inference rules. * RDF/XML, an XML-based syntax that was the first standard format for serializing RDF. * RDF/JSON, an alternative syntax for expressing RDF triples using a simple JSON notation. RDF/XML is sometimes misleadingly called simply RDF because it was introduced among the other W3C specifications defining RDF and it was historically the first W3C standard RDF serialization format. However, it is important to distinguish the RDF/XML format from the abstract RDF model itself. Although the RDF/XML format is still in use, other RDF serializations are now preferred by many RDF users, both because they are more human-friendly, and because some RDF graphs are not representable in RDF/XML due to restrictions on the syntax of XML QNames. With a little effort, virtually any arbitrary
XML Extensible Markup Language (XML) is a markup language #REDIRECT Markup language In computer text processing, a markup language is a system for annotation, annotating a document in a way that is Syntax (logic), syntactically distinguishable fro ...

XML
may also be interpreted as RDF using GRDDL (pronounced 'griddle'), Gleaning Resource Descriptions from Dialects of Languages. RDF triples may be stored in a type of database called a triplestore.


Resource identification

The subject of an RDF statement is either a uniform resource identifier (URI) or a blank node, both of which denote web resource, resources. Resources indicated by blank nodes are called anonymous resources. They are not directly identifiable from the RDF statement. The predicate is a URI which also indicates a resource, representing a relationship. The object is a URI, blank node or a Unicode string literal. As of RDF 1.1 resources are identified by Internationalized Resource Identifiers (IRIs); IRI are a generalization of URI. In Semantic Web applications, and in relatively popular applications of RDF like RSS (file format), RSS and FOAF (software), FOAF (Friend of a Friend), resources tend to be represented by URIs that intentionally denote, and can be used to access, actual data on the World Wide Web. But RDF, in general, is not limited to the description of Internet-based resources. In fact, the URI that names a resource does not have to be dereferenceable at all. For example, a URI that begins with "http:" and is used as the subject of an RDF statement does not necessarily have to represent a resource that is accessible via HTTP, nor does it need to represent a tangible, network-accessible resource — such a URI could represent absolutely anything. However, there is broad agreement that a bare URI (without a # symbol) which returns a 300-level coded response when used in an HTTP GET request should be treated as denoting the internet resource that it succeeds in accessing. Therefore, producers and consumers of RDF statements must agree on the semantics of resource identifiers. Such agreement is not inherent to RDF itself, although there are some controlled vocabularies in common use, such as Dublin Core Metadata, which is partially mapped to a URI space for use in RDF. The intent of publishing RDF-based ontologies on the Web is often to establish, or circumscribe, the intended meanings of the resource identifiers used to express data in RDF. For example, the URI:
http://www.w3.org/TR/2004/REC-owl-guide-20040210/wine#Merlot
is intended by its owners to refer to the class of all Merlot red wines by vintner (i.e., instances of the above URI each represent the class of all wine produced by a single vintner), a definition which is expressed by the OWL ontology — itself an RDF document — in which it occurs. Without careful analysis of the definition, one might erroneously conclude that an instance of the above URI was something physical, instead of a type of wine. Note that this is not a 'bare' resource identifier, but is rather a Uniform Resource Identifier#URI references, URI reference, containing the '#' character and ending with a fragment identifier.


Statement reification and context

The body of knowledge modeled by a collection of statements may be subjected to Reification (knowledge representation), reification, in which each ''statement'' (that is each triple ''subject-predicate-object'' altogether) is assigned a URI and treated as a resource about which additional statements can be made, as in "''Jane says that'' John is the author of document X". Reification is sometimes important in order to deduce a level of confidence or degree of usefulness for each statement. In a reified RDF database, each original statement, being a resource, itself, most likely has at least three additional statements made about it: one to assert that its subject is some resource, one to assert that its predicate is some resource, and one to assert that its object is some resource or literal. More statements about the original statement may also exist, depending on the application's needs. Borrowing from concepts available in logic (and as illustrated in graphical notations such as conceptual graphs and topic maps), some RDF model implementations acknowledge that it is sometimes useful to group statements according to different criteria, called ''situations'', ''contexts'', or ''scopes'', as discussed in articles by RDF specification co-editor Graham Klyne. For example, a statement can be associated with a context, named by a URI, in order to assert an "is true in" relationship. As another example, it is sometimes convenient to group statements by their source, which can be identified by a URI, such as the URI of a particular RDF/XML document. Then, when updates are made to the source, corresponding statements can be changed in the model, as well. Implementation of scopes does not necessarily require fully reified statements. Some implementations allow a single scope identifier to be associated with a statement that has not been assigned a URI, itself. Likewise ''named graphs'' in which a set of triples is named by a URI can represent context without the need to reify the triples.


Query and inference languages

The predominant query language for RDF graphs is
SPARQL SPARQL (pronounced " sparkle" , a recursive acronym A recursive acronym is an acronym An acronym is a word or name formed from the initial components of a longer name or phrase, usually using individual initial letters, as in NATO (North ...
. SPARQL is an SQL-like language, and a W3C recommendation, recommendation of the W3C as of January 15, 2008. The following is an example of a SPARQL query to show country capitals in Africa, using a fictional ontology: PREFIX ex: SELECT ?capital ?country WHERE Other non-standard ways to query RDF graphs include: * RDQL, precursor to SPARQL, SQL-like * Versa, compact syntax (non–SQL-like), solely implemented in 4Suite (Python (programming language), Python). * RQL, one of the first declarative languages for uniformly querying RDF schemas and resource descriptions, implemented in RDFSuite. * SeRQL, part of Sesame (framework), Sesame * XUL has a template element in which to declare rules for matching data in RDF. XUL uses RDF extensively for data binding. SHACL Advanced Features specification (W3C Working Group Note)
the most recent version
of which is maintained by the SHACL Community Group defines support for SHACL Rules, used for data transformations, inferences and mappings of RDF based on SHACL shapes.


Validation and description

The predominant language for describing and validating RDF graphs is
SHACL Shapes Constraint Language (SHACL) is a World Wide Web Consortium The World Wide Web Consortium (W3C) is the main international standards organization A standards organization, standards body, standards developing organization (SDO), or ...
(Shapes Constraint Language). SHACL specification is divided in two parts: SHACL Core and SHACL-SPARQL. SHACL Core consists of a list of built-in constraints such as cardinality, range of values and many others. SHACL-SPARQL describes SPARQL-based constraints and an extension mechanism to declare new constraint components. Other non-standard ways to describe and validate RDF graphs include: * SPARQL Inferencing Notation (SPIN) was based on SPARQL queries. It has been effectively deprecated in favor of SHACL. * ShEx (Shape Expressions) is a concise language for RDF validation and description.


Examples


Example 1: Description of a person named Eric Miller

The following example is taken from the W3C website describing a resource with statements "there is a Person identified by http://www.w3.org/People/EM/contact#me, whose name is Eric Miller, whose email address is e.miller123(at)example (changed for security purposes), and whose title is Dr." The resource "http://www.w3.org/People/EM/contact#me" is the subject. The objects are: * "Eric Miller" (with a predicate "whose name is"), * mailto:e.miller123(at)example (with a predicate "whose email address is"), and * "Dr." (with a predicate "whose title is"). The subject is a URI. The predicates also have URIs. For example, the URI for each predicate: * "whose name is" is http://www.w3.org/2000/10/swap/pim/contact#fullName, * "whose email address is" is http://www.w3.org/2000/10/swap/pim/contact#mailbox, * "whose title is" is http://www.w3.org/2000/10/swap/pim/contact#personalTitle. In addition, the subject has a type (with URI http://www.w3.org/1999/02/22-rdf-syntax-ns#type), which is person (with URI http://www.w3.org/2000/10/swap/pim/contact#Person). Therefore, the following "subject, predicate, object" RDF triples can be expressed: * http://www.w3.org/People/EM/contact#me, http://www.w3.org/2000/10/swap/pim/contact#fullName, "Eric Miller" * http://www.w3.org/People/EM/contact#me, http://www.w3.org/2000/10/swap/pim/contact#mailbox, mailto:e.miller123(at)example * http://www.w3.org/People/EM/contact#me, http://www.w3.org/2000/10/swap/pim/contact#personalTitle, "Dr." * http://www.w3.org/People/EM/contact#me, http://www.w3.org/1999/02/22-rdf-syntax-ns#type, http://www.w3.org/2000/10/swap/pim/contact#Person In standard N-Triples format, this RDF can be written as: "Eric Miller" . . "Dr." . . Equivalently, it can be written in standard Turtle (syntax) format as: @prefix eric: . @prefix contact: . @prefix rdf: . eric:me contact:fullName "Eric Miller" . eric:me contact:mailbox . eric:me contact:personalTitle "Dr." . eric:me rdf:type contact:Person . Or, it can be written in RDF/XML format as: Eric Miller Dr.


Example 2: The postal abbreviation for New York

Certain concepts in RDF are taken from logic and linguistics, where subject-predicate and subject-predicate-object structures have meanings similar to, yet distinct from, the uses of those terms in RDF. This example demonstrates: In the English language statement '' 'New York has the postal abbreviation NY' '','' 'New York' '' would be the subject, '' 'has the postal abbreviation' '' the predicate and '' 'NY' '' the object. Encoded as an RDF triple, the subject and predicate would have to be resources named by URIs. The object could be a resource or literal element. For example, in the N-Triples form of RDF, the statement might look like: "NY" . In this example, "urn:x-states:New%20York" is the URI for a resource that denotes the US state New York (state), New York, "http://purl.org/dc/terms/alternative" is the URI for a predicate (whose human-readable definition can be found at here ), and "NY" is a literal string. Note that the URIs chosen here are not standard, and don't need to be, as long as their meaning is known to whatever is reading them.


Example 3: A Wikipedia article about Tony Benn

In a like manner, given that "http://en.wikipedia.org/wiki/Tony_Benn" identifies a particular resource (regardless of whether that URI could be traversed as a hyperlink, or whether the resource is ''actually'' the Wikipedia article about Tony Benn), to say that the title of this resource is "Tony Benn" and its publisher is "Wikipedia" would be two assertions that could be expressed as valid RDF statements. In the N-Triples form of RDF, these statements might look like the following: "Tony Benn" . "Wikipedia" . To an English-speaking person, the same information could be represented simply as:
The title of this resource, which is published by Wikipedia, is 'Tony Benn'
However, RDF puts the information in a formal way that a machine can understand. The purpose of RDF is to provide an Semantics encoding, encoding and interpretation mechanism so that Resource (computer science), resources can be described in a way that particular software can understand it; in other words, so that software can access and use information that it otherwise couldn't use. Both versions of the statements above are wordy because one requirement for an RDF resource (as a subject or a predicate) is that it be unique. The subject resource must be unique in an attempt to pinpoint the exact resource being described. The predicate needs to be unique in order to reduce the chance that the idea of Title or Publisher will be ambiguous to software working with the description. If the software recognizes ''http://purl.org/dc/elements/1.1/title'' (a specific definition for the concept of a title established by the Dublin Core Metadata Initiative), it will also know that this title is different from a land title or an honorary title or just the letters t-i-t-l-e put together. The following example, written in Turtle, shows how such simple claims can be elaborated on, by combining multiple RDF vocabularies. Here, we note that the primary topic of the Wikipedia page is a "Person" whose name is "Tony Benn": @prefix rdf: . @prefix foaf: . @prefix dc: . dc:publisher "Wikipedia" ; dc:title "Tony Benn" ; foaf:primaryTopic [ a foaf:Person ; foaf:name "Tony Benn" ] .


Applications

* DBpedia – Extracts facts from Wikipedia articles and publishes them as RDF data. * YAGO (database), YAGO – Similar to DBpedia extracts facts from Wikipedia articles and publishes them as RDF data. * Wikidata – Collaboratively edited knowledge base hosted by the Wikimedia Foundation. * Creative Commons – Uses RDF to embed license information in web pages and mp3 files. * FOAF (software), FOAF (Friend of a Friend) – designed to describe person, people, their interests and interconnections. * Haystack (PIM), Haystack client – Semantic web browser from MIT CS & AI lab. * IDEAS Group – developing a formal Ontology components, 4D ontology for Enterprise Architecture using RDF as the encoding. * Microsoft shipped a product, Connected Services Framework, which provides RDF-based Profile Management capabilities. * MusicBrainz – Publishes information about Music Albums. * NEPOMUK (framework), NEPOMUK, an open-source software specification for a Social Semantic desktop uses RDF as a storage format for collected metadata. NEPOMUK is mostly known because of its integration into the KDE Software Compilation 4, KDE SC 4 desktop environment. * Cochrane (organisation), Cochrane is a global publisher of clinical study meta-analyses in evidence based healthcare. They use an ontology driven data architecture to semantically annotate their published reviews with RDF based structured data. * RDF Site Summary – one of several "RSS (file format), RSS" languages for publishing information about updates made to a web page; it is often used for disseminating news article summaries and sharing weblog content. * Simple Knowledge Organization System (SKOS) – a KR representation intended to support vocabulary/thesaurus applications * Semantically-Interlinked Online Communities, SIOC (Semantically-Interlinked Online Communities) – designed to describe online communities and to create connections between Internet-based discussions from message boards, weblogs and mailing lists. * Smart-M3 – provides an infrastructure for using RDF and specifically uses the ontology agnostic nature of RDF to enable heterogeneous mashing-up of information * LV2 - a libre plugin format using Turtle to describe API/ABI capabilities and properties Some uses of RDF include research into social networking. It will also help people in business fields understand better their relationships with members of industries that could be of use for product placement. It will also help scientists understand how people are connected to one another. RDF is being used to have a better understanding of road traffic patterns. This is because the information regarding traffic patterns is on different websites, and RDF is used to integrate information from different sources on the web. Before, the common methodology was using keyword searching, but this method is problematic because it does not consider synonyms. This is why ontologies are useful in this situation. But one of the issues that comes up when trying to efficiently study traffic is that to fully understand traffic, concepts related to people, streets, and roads must be well understood. Since these are human concepts, they require the addition of fuzzy logic. This is because values that are useful when describing roads, like slipperiness, are not precise concepts and cannot be measured. This would imply that the best solution would incorporate both fuzzy logic and ontology.Traffic Information Retrieval Based on Fuzzy Ontology and RDF on the Semantic Web By Jun Zhai, Yi Yu, Yiduo Liang, and Jiatao Jiang (2008)


See also

;Notations for RDF * TriG (syntax), TRiG * TriX (syntax), TRiX * RDF/XML * RDFa * JSON-LD * Notation3 ;Similar concepts * Entity–attribute–value model * Graph theory – an RDF model is a labeled, directed multi-graph. * Tag (metadata) * SciCrunch * Semantic network ; Other (unsorted): * Semantic technology * Business Intelligence 2.0 (BI 2.0) * Data portability * EU Open Data Portal * Folksonomy * LSID - Life Science Identifier * Swoogle * Universal Networking Language (UNL) * VoID


References


Citations


Sources

*


Further reading


W3C's RDF at W3C
specifications, guides, and resources
RDF Semantics
specification of semantics, and complete systems of inference rules for both RDF and RDFS


External links

* {{Authority control Resource Description Framework, Knowledge representation World Wide Web Consortium standards XML XML-based standards Metadata Semantic Web Bibliography file formats Modeling languages