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 rel ...
s). It is based on the idea of making
statements about
resources (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 denoting "has the color", and an
object 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 ...
in
object-oriented design: entity (sky), attribute (color), and value (blue).
RDF is an abstract model with several
serialization formats (being essentially specialized
file formats). In addition the particular encoding for resources or triples can vary from format to format.
This mechanism for describing resources is a major
component 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 s ...
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 ...
. 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 ...
better suited to certain kinds 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 ...
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 exis ...
models.
As
RDFS,
OWL 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 languages 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 (PICS), an early web content labelling system,
but the project was also shaped by ideas from
Dublin Core, and from the
Meta Content Framework (MCF),
which had been developed during 1995 to 1997 by
Ramanathan V. Guha at
Apple and
Tim Bray at
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 on ...
.
A first public draft of RDF appeared in October 1997, issued by a W3C working group that included representatives from
IBM,
Microsoft,
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 on ...
,
Nokia,
Reuters,
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 demonstra ...
, and the
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 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, around ILRT at
Bristol University
, mottoeng = earningpromotes one's innate power (from Horace, ''Ode 4.4'')
, established = 1595 – Merchant Venturers School1876 – University College, Bristol1909 – received royal charter
, type ...
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 ...
.
RSS 1.0 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 so ...
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.
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), a Canadian ani ...
s and
integers
; : 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, where it is extended.
Serialization formats
Several common
serialization formats are in use, including:
*
Turtle,
a compact, human-friendly format.
*
TriG,
an extension of Turtle to datasets.
*
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
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 dat ...
,
a
JSON-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,
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 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
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, both of which denote
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 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 so ...
(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, w ...
, 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
Merlot is a dark blue–colored wine grape variety, that is used as both a blending grape and for varietal wines. The name ''Merlot'' is thought to be a diminutive of ''merle'', the French name for the blackbird, probably a reference to the c ...
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
In computer hypertext, a URI fragment is a string of characters that refers to a resource that is subordinate to another, primary resource. The primary resource is identified by a Uniform Resource Identifier (URI), and the fragment identifier p ...
.
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 (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 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 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).
* 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 c ...
*
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 versionof 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 (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 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 ca ...
(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
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 i ...
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 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
encoding and interpretation mechanism so that
resources 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 consist ...
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 or
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 defini ...
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
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 semantica ...
– 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 Wiki, 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 lice ...
– 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 releas ...
– Uses RDF to embed license information in web pages and mp3 files.
*
FOAF (Friend of a Friend) – designed to describe
people
A person ( : 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 propert ...
, their interests and interconnections.
*
Haystack client – Semantic web browser from MIT CS & AI lab.
*
IDEAS Group – 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, 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 "
RSS" 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 s ...
content.
*
Simple Knowledge Organization System (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-ins and matching host applications. It includes support for the synthesis and processing of digital audio and CV, events such as MIDI and OSC, and provides a free altern ...
- 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
Fuzzy logic is a form of many-valued logic in which the truth value of variables may be any real number between 0 and 1. It is employed to handle the concept of partial truth, where the truth value may range between completely true and completely ...
. 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
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TRiG
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TRiX
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RDF/XML
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RDFa
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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 dat ...
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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 ...
;Similar concepts
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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 ...
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Graph theory
In mathematics, graph theory is the study of ''graphs'', which are mathematical structures used to model pairwise relations between objects. A graph in this context is made up of '' vertices'' (also called ''nodes'' or ''points'') which are conne ...
– an RDF model is a labeled, directed multi-graph.
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Tag (metadata)
In information systems, a tag is a keyword or term assigned to a piece of information (such as an Internet bookmark, multimedia, database record, or computer file). This kind of metadata helps describe an item and allows it to be found again ...
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SciCrunch
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Semantic network
; Other (unsorted):
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Semantic technology
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Business Intelligence 2.0 (BI 2.0)
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Data portability
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EU Open Data Portal
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Folksonomy
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LSID - Life Science Identifier
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Swoogle
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Universal Networking Language (UNL)
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VoID
References
Citations
Sources
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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
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{{Authority control
Knowledge representation
World Wide Web Consortium standards
XML
XML-based standards
Metadata
Semantic Web
Bibliography file formats
Modeling languages