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 syntax notations and data serialization formats with Turtle (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 is a standard query language for RDF graphs. RDFS, OWL and SHACL are ontology languages 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, a class diagram in the Unified Modeling Language (UML) is a type of static structure diagram that describes the structure of a system by showing the system's classes, their attributes, operations (or methods), and the rela ...

s). It is based on the idea of making statements about

resource Resource refers to all the materials available in our environment which are technologically accessible, economically feasible and culturally sustainable and help us to satisfy our needs and wants. Resources can broadly be classified upon their ...

s (in particular web resources) in expressions of the form subject–predicate–object, known as '' triples''. 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 denoting "the sky", a

predicate Predicate or predication may refer to: * Predicate (grammar), in linguistics * Predication (philosophy) * several closely related uses in mathematics and formal logic: **Predicate (mathematical logic) **Propositional function **Finitary relation, o ...

denoting "has the color", and an

object Object may refer to: General meanings * Object (philosophy), a thing, being, or concept ** Object (abstract), an object which does not exist at any particular time or place ** Physical object, an identifiable collection of matter * Goal, an ...

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 actuall ...

object-oriented design Object-oriented design (OOD) is the process of planning a Object-oriented programming, system of interacting objects for the purpose of solving a software problem. It is one approach to software design. Overview An Object (computer science), obje ...

: entity (sky), attribute (color), and value (blue). RDF is an abstract model with several serialization formats (being essentially specialized

file format A file format is a standard way that information is encoded for storage in a computer file. It specifies how bits are used to encode information in a digital storage medium. File formats may be either proprietary or free. Some file formats ...

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 Circuit Component may refer to: •Are devices that perform functions when they are connected in a circuit. In engineering, science, and technology Generic systems * System components, an entity with discrete structure, such as an assem ...

in the W3C's 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 enabling documents and other web resources to be accessed over the Internet. Documents and downloadable media are made available to the network through web se ...

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 epistemic property of beliefs which a person has no rational grounds for doubting. One standard way of defining epistemic certainty is that a belief is certain if and o ...

. 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 and information of an organization. It refers to a multidisciplinary approach to achieve organisational objectives by making ...

applications unrelated to Semantic Web activity. A collection of RDF statements intrinsically represents a labeled,

directed Director may refer to: Literature * ''Director'' (magazine), a British magazine * ''The Director'' (novel), a 1971 novel by Henry Denker * ''The Director'' (play), a 2000 play by Nancy Hasty Music * Director (band), an Irish rock band * ''D ...

multi-graph. This makes an RDF

data model A data model is an abstract model that organizes elements of data and standardizes how they relate to one another and to the properties of real-world entities. For instance, a data model may specify that the data element representing a car be co ...

better suited to certain kinds of knowledge representation than are other relational or

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 exi ...

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 data model, providing basic elements for the descr ...

OWL Owls are birds from the order Strigiformes (), which includes over 200 species of mostly solitary and nocturnal birds of prey typified by an upright stance, a large, broad head, binocular vision, binaural hearing, sharp talons, and feathers a ...

and

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 ...

demonstrate, one can build additional

ontology language In computer science and artificial intelligence, ontology languages are formal languages used to construct ontologies. They allow the encoding of knowledge about specific domains and often include reasoning rules that support the processing of th ...

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 to label webpages to help parents and teachers control what children and students could access on the Internet. The W3C Protocol for Web Des ...

(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 (DCMES), is a set of fifteen "core" elements (properties) for describing resources. This fifteen-element Dublin Core has ...

, and from the

Meta Content Framework Meta Content Framework (MCF) is a specification of a content format for structuring metadata about web sites and other data. History MCF was developed by Ramanathan V. Guha at Apple Computer's Advanced Technology Group between 1995 and 1997. Roo ...

(MCF), which had been developed during 1995 to 1997 by Ramanathan V. Guha at

Apple An apple is an edible fruit produced by an apple tree (''Malus domestica''). Apple fruit tree, trees are agriculture, cultivated worldwide and are the most widely grown species in the genus ''Malus''. The tree originated in Central Asia, wh ...

and

Tim Bray Timothy William Bray (born June 21, 1955) is a Canadian software developer, environmentalist, political activist and one of the co-authors of the original XML specification. He worked for Amazon Web Services from December 2014 until May 2020 w ...

Netscape Netscape Communications Corporation (originally Mosaic Communications Corporation) was an American independent computer services company with headquarters in Mountain View, California and then Dulles, Virginia. Its Netscape web browser was onc ...

. A first public draft of RDF appeared in October 1997, issued by a W3C working group that included representatives from IBM,

Microsoft Microsoft Corporation is an American multinational technology corporation producing computer software, consumer electronics, personal computers, and related services headquartered at the Microsoft Redmond campus located in Redmond, Washing ...

Nokia Nokia Corporation (natively Nokia Oyj, referred to as Nokia) is a Finnish multinational corporation, multinational telecommunications industry, telecommunications, technology company, information technology, and consumer electronics corporatio ...

Reuters Reuters ( ) is a news agency owned by Thomson Reuters Corporation. 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 was estab ...

SoftQuad SoftQuad 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 demonstrat ...

, and the

University of Michigan , mottoeng = "Arts, Knowledge, Truth" , former_names = Catholepistemiad, or University of Michigania (1817–1821) , budget = $10.3 billion (2021) , endowment = $17 billion (2021)As o ...

. 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 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. 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, ceremonial county and unitary authority in England. Situated on the River Avon, it is bordered by the ceremonial counties of Gloucestershire to the north and Somerset to the south. Bristol is the most populous city in ...

, around ILRT at Bristol University and HP Labs, and in Boston at

MIT The Massachusetts Institute of Technology (MIT) is a private land-grant research university in Cambridge, Massachusetts. Established in 1861, MIT has played a key role in the development of modern technology and science, and is one of the m ...

RSS 1.0 RSS ( RDF Site Summary or Really Simple Syndication) is a web feed that allows users and applications to access updates to websites in a standardized, computer-readable format. Subscribing to RSS feeds can allow a user to keep track of many di ...

and

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 ...

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

= ; : the class of XML literal values ; : the class of properties ; : the class of RDF statements ; , , : containers of alternatives, unordered containers, and ordered containers (rdfs:Container is a super-class of the three) ; : the class of RDF Lists ; : an instance of rdf:List representing the empty list

= rdfs

= ; : the class resource, everything ; : the class of literal values, e.g. strings and

integer An integer is the number zero (), a positive natural number (, , , etc.) or a negative integer with a minus sign (−1, −2, −3, etc.). The negative numbers are the additive inverses of the corresponding positive numbers. In the language ...

s ; : the class of classes ; : the class of RDF datatypes ; : the class of RDF containers ; : the class of container membership properties, rdf:_1, rdf:_2, ..., all of which are sub-properties of rdfs:member

Properties

=rdf

= ; : an instance of rdf:Property used to state that a resource is an instance of a class ; : the first item in the subject RDF list ; : the rest of the subject RDF list after rdf:first ; : idiomatic property used for structured values ; : the subject of the RDF statement ; : the predicate of the RDF statement ; : the object of the RDF statement rdf:Statement, rdf:subject, rdf:predicate, rdf:object are used for reification (see below).

=rdfs

= ; : the subject is a subclass of a class ; : the subject is a subproperty of a property ; : a domain of the subject property ; : a range of the subject property ; : a human-readable name for the subject ; : a description of the subject resource ; : a member of the subject resource ; : further information about the subject resource ; : the definition of the subject resource This vocabulary is used as a foundation for

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 ...

, where it is extended.

Serialization formats

Several common serialization formats are in use, including: *

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 ...

, a compact, human-friendly format. * TriG, an extension of Turtle to datasets. *

N-Triples N-Triples is a format for storing and transmitting data. It is a line-based, plain text serialisation format for RDF (Resource Description Framework) graphs, and a subset of the Turtle (Terse RDF Triple Language) format. N-Triples should not be ...

, a very simple, easy-to-parse, line-based format that is not as compact as Turtle. *

N-Quads N-Triples is a format for storing and transmitting data. It is a line-based, plain text serialisation format for Resource Description Framework, RDF (Resource Description Framework) graphs, and a subset of the Turtle (syntax), Turtle (Terse RDF Tr ...

, a superset of N-Triples, for serializing multiple RDF graphs. *

JSON-LD JSON-LD (JavaScript Object Notation for Linked Data) is a method of encoding linked data using JSON. One goal for JSON-LD was to require as little effort as possible from developers to transform their existing JSON to JSON-LD. JSON-LD allows data ...

, a

JSON JSON (JavaScript Object Notation, pronounced ; also ) is an open standard file format and data interchange format that uses human-readable text to store and transmit data objects consisting of attribute–value pairs and arrays (or other ser ...

-based serialization. * N3 or

Notation3 Notation3, or N3 as it is more commonly known, is a shorthand non-XML serialization of Resource Description Framework models, designed with human-readability in mind: N3 is much more compact and readable than XML RDF notation. The format is being ...

, 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 RDF/XML is a syntax,RDF/XML Syntax Specification
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

QName A QName, or qualified name, is the fully qualified name of an element, attribute, or identifier in an XML document. A QName concisely associates the URI of an XML namespace with the ''local name'' of an element, attribute, or identifier in that n ...

s. With a little effort, virtually any arbitrary

may also be interpreted as RDF using

GRDDL GRDDL (pronounced "''griddle''") is a markup format for Gleaning Resource Descriptions from Dialects of Languages. It is a W3C Recommendation, and enables users to obtain RDF triples out of XML documents, including XHTML. The GRDDL specification s ...

(pronounced 'griddle'), Gleaning Resource Descriptions from Dialects of Languages. RDF triples may be stored in a type of database called a

triplestore A triplestore or RDF store is a purpose-built database for the storage and retrieval of triples through semantic queries. A triple is a data entity composed of subject–predicate–object, like "Bob is 35" or "Bob knows Fred". Much like a relat ...

Resource identification

The subject of an RDF statement is either a

uniform resource identifier A Uniform Resource Identifier (URI) is a unique sequence of characters that identifies a logical or physical resource used by web technologies. URIs may be used to identify anything, including real-world objects, such as people and places, conc ...

(URI) or a

blank node In RDF, a blank node (also called ''bnode'') is a node in an RDF graph representing a resource for which a URI or literal is not given. The resource represented by a blank node is also called an anonymous resource. According to the RDF standard ...

, both of which denote

s. Resources indicated by

s 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 Unicode, formally The Unicode Standard,The formal version reference is is an information technology Technical standard, standard for the consistent character encoding, encoding, representation, and handling of Character (computing), text expre ...

string literal A string literal or anonymous string is a string value in the source code of a computer program. Modern programming languages commonly use a quoted sequence of characters, formally " bracketed delimiters", as in x = "foo", where "foo" is a string ...

. 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 RSS ( RDF Site Summary or Really Simple Syndication) is a web feed that allows users and applications to access updates to websites in a standardized, computer-readable format. Subscribing to RSS feeds can allow a user to keep track of many di ...

and

(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 The Hypertext Transfer Protocol (HTTP) is an application layer protocol in the Internet protocol suite model for distributed, collaborative, hypermedia information systems. HTTP is the foundation of data communication for the World Wide Web, ...

, 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 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, 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 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 ...

(and as illustrated in graphical notations such as conceptual graphs and

topic map A topic map is a standard for the representation and interchange of knowledge, with an emphasis on the findability of information. Topic maps were originally developed in the late 1990s as a way to represent back-of-the-book index structures s ...

s), 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 for SPARQL Protocol and RDF Query Language) is an RDF query language—that is, a semantic query language for databases—able to retrieve and manipulate data stored in Resource Description ...

. SPARQL is an SQL-like language, and a recommendation of the

W3C 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 ...

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 Python may refer to: Snakes * Pythonidae, a family of nonvenomous snakes found in Africa, Asia, and Australia ** ''Python'' (genus), a genus of Pythonidae found in Africa and Asia * Python (mythology), a mythical serpent Computing * Python (pro ...

). * RQL, one of the first declarative languages for uniformly querying RDF schemas and resource descriptions, implemented in RDFSuite. * SeRQL, part of

Sesame Sesame ( or ; ''Sesamum indicum'') is a flowering plant in the genus ''Sesamum'', also called benne. Numerous wild relatives occur in Africa and a smaller number in India. It is widely naturalized in tropical regions around the world and is cu ...

XUL XUL ( ), which stands for XML User Interface Language, is a user interface markup language developed by Mozilla. XUL is an XML dialect for writing graphical user interfaces, enabling developers to write user interface elements in a manner sim ...

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

(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 (ShEx) is a data modelling language for validating and describing a Resource Description Framework (RDF). It was proposed at the 2012 RDF Validation Workshop as a high-level, concise language for RDF validation. The shapes c ...

(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

and

linguistics Linguistics is the scientific study of human language. It is called a scientific study because it entails a comprehensive, systematic, objective, and precise analysis of all aspects of language, particularly its nature and structure. Linguis ...

, 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 English is a West Germanic language of the Indo-European language family, with its earliest forms spoken by the inhabitants of early medieval England. It is named after the Angles, one of the ancient Germanic peoples that migrated to the is ...

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, "http://purl.org/dc/terms/alternative" is the URI for a predicate (whose human-readable definition can be found here ), and "NY" is a literal string. Note that the URIs chosen here are not standard, and do not 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 Wikipedia is a multilingual free online encyclopedia written and maintained by a community of volunteers, known as Wikipedians, through open collaboration and using a wiki-based editing system. Wikipedia is the largest and most-read refer ...

article about

Tony Benn Anthony Neil Wedgwood Benn (3 April 1925 – 14 March 2014), known between 1960 and 1963 as Viscount Stansgate, was a British politician, writer and diarist who served as a Cabinet minister in the 1960s and 1970s. A member of the Labour Party, ...

), 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

encoding In communications and information processing, code is a system of rules to convert information—such as a letter, word, sound, image, or gesture—into another form, sometimes shortened or secret, for communication through a communication ...

and interpretation mechanism so that

resources Resource refers to all the materials available in our environment which are technologically accessible, economically feasible and culturally sustainable and help us to satisfy our needs and wants. Resources can broadly be classified upon their av ...

can be described in a way that particular

software Software is a set of computer programs and associated documentation and data. This is in contrast to hardware, from which the system is built and which actually performs the work. At the lowest programming level, executable code consists ...

can understand it; in other words, so that software can access and use information that it otherwise could not 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 A title is one or more words used before or after a person's name, in certain contexts. It may signify either generation, an official position, or a professional or academic qualification. In some languages, titles may be inserted between the f ...

Publisher Publishing is the activity of making information, literature, music, software and other content available to the public for sale or for free. Traditionally, the term refers to the creation and distribution of printed works, such as books, newsp ...

will be ambiguous to software working with the description. If the software recognizes ''http://purl.org/dc/elements/1.1/title'' (a specific

definition A definition is a statement of the meaning of a term (a word, phrase, or other set of symbols). Definitions can be classified into two large categories: intensional definitions (which try to give the sense of a term), and extensional definitio ...

for the

concept Concepts are defined as abstract ideas. They are understood to be the fundamental building blocks of the concept behind principles, thoughts and beliefs. They play an important role in all aspects of cognition. As such, concepts are studied by s ...

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 DBpedia (from "DB" for " database") is a project aiming to extract structured content from the information created in the Wikipedia project. This structured information is made available on the World Wide Web. DBpedia allows users to semanti ...

– Extracts facts from Wikipedia articles and publishes them as RDF data. * YAGO – Similar to DBpedia extracts facts from Wikipedia articles and publishes them as RDF data. *

Wikidata Wikidata is a collaboratively edited multilingual knowledge graph hosted by the Wikimedia Foundation. It is a common source of open data that Wikimedia projects such as Wikipedia, and anyone else, can use under the CC0 public domain license ...

– Collaboratively edited knowledge base hosted by the Wikimedia Foundation. *

Creative Commons Creative Commons (CC) is an American non-profit organization and international network devoted to educational access and expanding the range of creative works available for others to build upon legally and to share. The organization has release ...

– Uses RDF to embed license information in web pages and mp3 files. * FOAF (Friend of a Friend) – designed to describe

people A person (plural, : people) is a being that has certain capacities or attributes such as reason, morality, consciousness or self-consciousness, and being a part of a culturally established form of social relations such as kinship, ownership of pr ...

, their interests and interconnections. * Haystack client – Semantic web browser from MIT CS & AI lab. *

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 ...

– developing a formal 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 MusicBrainz is a MetaBrainz project that aims to create a collaborative music database that is similar to the freedb project. MusicBrainz was founded in response to the restrictions placed on the Compact Disc Database (CDDB), a database for so ...

– Publishes information about Music Albums. *

NEPOMUK Nepomuk (; german: Pomuk) is a town in Plzeň-South District in the Plzeň Region of the Czech Republic. It has about 3,700 inhabitants. It is known as the birthplace of Saint John of Nepomuk, who was born here around 1340 and whose statue can b ...

, 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 SC 4 desktop environment. * 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 "

" languages for publishing information about updates made to a web page; it is often used for disseminating news article summaries and sharing

weblog A blog (a truncation of "weblog") is a discussion or informational website published on the World Wide Web consisting of discrete, often informal diary-style text entries (posts). Posts are typically displayed in reverse chronological order ...

content. *

Simple Knowledge Organization System 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 ...

(SKOS) – a KR representation intended to support vocabulary/thesaurus applications * 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 LV2 (LADSPA Version 2) is a set of royalty-free open standards for plug-in (computing), plug-ins and matching host applications. It includes support for the audio synthesis, synthesis and digital signal processing, processing of digital audio and ...

- 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)

References

Citations

Sources

External links

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