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Encyclopedia > Resource Description Framework
Resource Description Framework
File extension: .rdf
MIME type: application/rdf+xml
Developed by: World Wide Web Consortium
Type of format: semantic web
Container for: FOAF, SKOS, ...
Standard(s): Recommendation

Resource Description Framework (RDF) is a family of World Wide Web Consortium (W3C) specifications originally designed as a metadata model but which has come to be used as a general method of modeling information, through a variety of syntax formats. A filename extension is a suffix to the name of a computer file applied to show its format. ... Multipurpose Internet Mail Extensions (MIME) is an Internet Standard that extends the format of e-mail to support text in character sets other than US-ASCII, non-text attachments, multi-part message bodies, and header information in non-ASCII character sets. ... The semantic web is an evolving extension of the World Wide Web in which web content can be expressed not only in natural language, but also in a form that can be understood, interpreted and used by software agents, thus permitting them to find, share and integrate information more easily. ... FOAF (Friend of a Friend) is a project for machine-readable modelling of homepage-like content and social networks founded by Libby Miller and Dan Brickley. ... SKOS or Simple Knowledge Organisation System is a family of formal languages designed for representation of thesauri, classification schemes, taxonomies, subject-heading systems, or any other type of structured controlled vocabulary. ... Standards are produced by many organizations, some for internal usage only, others for use by a groups of people, groups of companies, or a subsection of an industry. ... The World Wide Web Consortium (W3C) is the main international standards organization for the World Wide Web (W3). ... In engineering and manufacturing, the term specification has the following meanings: Technical requirement A specification is a set of requirements. ... Metadata is data about data. ... An abstract model (or conceptual model) is a theoretical construct that represents physical, biological or social processes, with a set of variables and a set of logical and quantitative relationships between them. ...


The RDF metadata model is based upon the idea of making statements about resources in the form of subject-predicate-object expressions, called triples in RDF terminology. 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 a triple of specially formatted strings: a subject denoting "the sky", a predicate denoting "has the color", and an object denoting "blue". The term statement can have several meanings: In programming, a statement is an instruction to execute something that will not return a value. ... The term resource is a foundational term in World Wide Web architecture because it is the root of Uniform Resource Identifiers, also known as URIs and URLs. ... In mathematics, a triple is an n-tuple with n being 3. ... In biology, a trait or character is a genetically inherited feature of an organism. ... Aspect is a piece of information about a topic, usually on look and appearance. ... In computer programming and some branches of mathematics, strings are sequences of various simple objects. ... In linguistics and logic, a predicate is an expression that can be true of something. ...


This mechanism for describing resources is a major component in what is proposed by the W3C's Semantic Web activity: an evolutionary stage of the World Wide Web 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. RDF's simple data model and ability to model disparate, abstract concepts has also led to its increasing use in knowledge management applications unrelated to Semantic Web activity. It has been suggested that this article or section be merged with Component-based software engineering. ... The semantic web is an evolving extension of the World Wide Web in which web content can be expressed not only in natural language, but also in a form that can be understood, interpreted and used by software agents, thus permitting them to find, share and integrate information more easily. ... WWWs historical logo designed by Robert Cailliau The World Wide Web (or simply the Web) is a system of interlinked, hypertext documents that runs over the Internet. ... A related article is titled uncertainty. ... Knowledge management comprises a range of practices used by organisations to identify, create, represent, and distribute knowledge for reuse, awareness, and learning across the organisations. ...

Contents

History

There were several ancestors to W3C's RDF. Technically the closest was MCF, a project initiated by Ramanathan V. Guha while at Apple Computer and continued, with contributions from Tim Bray, during his tenure at Netscape Communications Corporation. Ideas from the Dublin Core community, and from PICS, the Platform for Internet Content Selection (W3C's early Web content labelling system) were also key in shaping the direction of the RDF project. Meta Content Framework (MCF) was a specification of a format for structuring metadata information about web sites and other data. ... Ramanathan V. Guha (1965) is an Indian computer scientist. ... Apple Inc. ... Timothy William Bray (born 1955), commonly known as Tim Bray, co-invented XML and XML namespaces while an Invited Expert at the World Wide Web Consortium between 1996 and 1999. ... Netscape Communications Corporation was the publisher of the Netscape Navigator web browser as well as many other internet and intranet client and server software products. ... The introduction to this article provides insufficient context for those unfamiliar with the subject matter. ... The Platform for Internet Content Selection is a specification created by W3C that uses metadata to label webpages so that parents and teachers to help control what children and students could access on the Internet. ...


The W3C published a specification for RDF's data model and XML syntax as a Recommendation in 1999. Work then began on a new version that was published as a set of related specifications in 2004. While there are a few implementations based on the 1999 Recommendation that have yet to be completely updated, adoption of the improved specifications has been rapid since they were developed in full public view, unlike some earlier W3C technologies. Most newcomers to RDF are unaware that the older specifications even exist. The Extensible Markup Language (XML) is a W3C-recommended general-purpose markup language that supports a wide variety of applications. ...


MIME media type application/rdf+xml was registered by RFC 3870. It recommends RDF documents to follow the new specifications. Multipurpose Internet Mail Extensions (MIME) is an Internet Standard that extends the format of e-mail to support text in character sets other than US-ASCII, non-text attachments, multi-part message bodies, and header information in non-ASCII character sets. ...


Ontologies

A collection of RDF statements intrinsically represents a labeled, directed pseudo-graph. As such, an RDF-based data model is more naturally suited to certain kinds of knowledge representation than the relational model and other ontological models traditionally used in computing today. However, in practice, RDF data is often stored in relational database representations sometimes also called triple stores. As RDFS and OWL demonstrate, additional ontology languages can be built upon RDF. In both computer science and information science, an ontology is a data model that represents a domain and is used to reason about the objects in that domain and the relations between them. ... Graph theory is a growth area in mathematical research, and has a large specialized vocabulary. ... A data model is a model that describes how data are represented and used in an abstract way. ... Knowledge representation is an issue that arises in both cognitive science and artificial intelligence. ... The relational model for database management is a database model based on predicate logic and set theory. ... In both computer science and information science, an ontology is a data model that represents a domain and is used to reason about the objects in that domain and the relations between them. ... A relational database management system (RDBMS) is a database management system (DBMS) that is based on the relational model as introduced by Edgar F. Codd. ... ... The Web Ontology Language (OWL) is a language for defining and instantiating Web ontologies. ... In computer science, an ontology is the attempt to formulate an exhaustive and rigorous conceptual schema within a given domain, a typically hierarchical data structure containing all the relevant entities and their relationships and rules (theorems, regulations) within that domain. ...


Resource identification

The subject of an RDF statement is a resource, possibly as named by a Uniform Resource Identifier (URI). Some resources are unnamed and are called blank nodes or anonymous resources. They are not directly identifiable. The predicate is a resource as well, representing a relationship. The object is a resource or a Unicode string literal. The term resource is a foundational term in World Wide Web architecture because it is the root of Uniform Resource Identifiers, also known as URIs and URLs. ... A Uniform Resource Identifier (URI), is a compact string of characters used to identify or name a resource. ... In RDF, a blank node or anonymous resource or bnode) is a resource, or node in an RDF graph, which is not identified by a URI. A bank node can be used as subject or object in an RDF triple. ... Unicode is an industry standard designed to allow text and symbols from all of the writing systems of the world to be consistently represented and manipulated by computers. ... In computer programming and some branches of mathematics, strings are sequences of various simple objects. ...


In Semantic Web applications, and in relatively popular applications of RDF like RSS and FOAF (Friend of a Friend), resources tend to be represented by URIs that intentionally denote actual, accessible 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 denote the abstract notion of world peace, if desired. For RSS feeds from Wikipedia, see Wikipedia:Syndication. ... FOAF (Friend of a Friend) is a project for machine-readable modelling of homepage-like content and social networks founded by Libby Miller and Dan Brickley. ... HTTP (for HyperText Transfer Protocol) is the primary method used to convey information on the World Wide Web. ...


Therefore, it is necessary for producers and consumers of RDF statements to be in agreement 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 introduction to this article provides insufficient context for those unfamiliar with the subject matter. ...


Examples

Example 1: 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: Logic, from Classical Greek λόγος logos (the word), is the study of the principles and criteria of valid inference and demonstration. ... Linguistics is the scientific study of language, which can be theoretical or applied. ... The introduction to this article provides insufficient context for those unfamiliar with the subject matter. ...


In the English language statement 'New York has the postal abbreviation of NY' , 'New York' would be the subject, 'has the postal abbreviation' the predicate and 'NY' the object. The English language is a West Germanic language that originates in England. ...


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:

<urn:states:New%20York> <http://purl.org/dc/terms/alternative> "NY" .

In this example, "urn:states:New%20York" is the URI for a resource that denotes the U.S. state New York, "http://purl.org/dc/terms/alternative" is the URI for a predicate (whose human-readable definition can be found at [1]), 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. NY redirects here. ...


N-Triples is just one of several standard serialization formats for RDF. The triple above can also be equivalently represented in the standard RDF/XML format as: In computer science, in the context of data storage and transmission in programming languages like Java, serialization is the process of saving an object onto a storage medium (such as a file, or a memory buffer) or to transmit it across a network connection link, either as a series of...

 <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:terms="http://purl.org/dc/terms/"> <rdf:Description rdf:about="urn:states:New%20York"> <terms:alternative>NY</terms:alternative> </rdf:Description> </rdf:RDF> 

However, because of the restrictions on the syntax of QNames (such as terms:alternative above), there are some RDF graphs that are not representable with RDF/XML.


Example 2: 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: Wikipedia - Wikipedia, the free encyclopedia /**/ @import /skins-1. ... Tony Benn about to join March 2005 anti-war demo in London Anthony Neil Wedgwood Benn (born April 3, 1925), known as Tony Benn, formerly 2nd Viscount Stansgate, is a British politician on the left of the Labour Party. ...

<http://en.wikipedia.org/wiki/Tony_Benn> <http://purl.org/dc/elements/1.1/title> "Tony Benn" .
<http://en.wikipedia.org/wiki/Tony_Benn> <http://purl.org/dc/elements/1.1/publisher> "Wikipedia" .

And these statements might be expressed in RDF/XML as:

 <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:dc="http://purl.org/dc/elements/1.1/"> <rdf:Description rdf:about="http://en.wikipedia.org/wiki/Tony_Benn"> <dc:title>Tony Benn</dc:title> <dc:publisher>Wikipedia</dc:publisher> </rdf:Description> </rdf:RDF> 

Of course, 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 the 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 can understand it; in other words, so that software can access and use data that it otherwise couldn't. The word encoding has a number of meanings. ... A resource, also referred to as system resource, is any physical or virtual system component of a computer system with limited availability. ... Computer software (or simply software) refers to one or more computer programs and data held in the storage of a computer for some purpose. ...


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. A title is a prefix or suffix added to a persons name to signify either veneration, an official position or a professional or academic qualification. ... A publisher is a person or entity which engages in the act of publishing. ... This page is a candidate to be moved to Wiktionary. ... A definition is a form of words which states the meaning of a term. ... A concept is an abstract idea or a mental symbol, typically associated with a corresponding representation in language or symbology, that denotes all of the objects in a given category or class of entities, interactions, phenomena, or relationships between them. ... The introduction to this article provides insufficient context for those unfamiliar with the subject matter. ...


The following example 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":

 <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" xmlns:foaf="http://xmlns.com/foaf/0.1/" xmlns:dc="http://purl.org/dc/elements/1.1/"> <rdf:Description rdf:about="http://en.wikipedia.org/wiki/Tony_Benn"> <dc:title>Tony Benn</dc:title> <dc:publisher>Wikipedia</dc:publisher> <foaf:primaryTopic> <foaf:Person> <foaf:name>Tony Benn</foaf:name> </foaf:Person> </foaf:primaryTopic> </rdf:Description> </rdf:RDF> 

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. Reification, in the context of object-oriented programming, is the implementation of an abstract behavior. ...


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 [2] [3]. 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. Logic, from Classical Greek λόγος logos (the word), is the study of the principles and criteria of valid inference and demonstration. ... Introduction John F. Sowas Conceptual graphs (CGs) are a system of logic based on the existential graphs of Charles Sanders Peirce and the semantic networks of artificial intelligence. ... Topic Maps are an ISO standard for the representation and interchange of knowledge, with an emphasis on the findability of information. ...


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. [4] [5]


In first-order logic, as facilitated by RDF without scopes, the only metalevel relation is negation, but the ability to generally state propositions about nested contexts allows RDF to comprise a metalanguage that can be used to define modal and higher-order logic. First-order logic (FOL) is a universal language in symbolic science, and is in use everyday by mathematicians, philosophers, linguists, computer scientists and practitioners of artificial intelligence. ... Negation (i. ... In mathematics, higher-order logic is distinguished from first-order logic in a number of ways. ...


Query and inference languages

Main article: RDF query language

Several query languages for RDF graphs have emerged. RDF query languages allow expressions to be written that can be evaluated against a collection of statements in order to produce, for example, a narrowed set of statements, resources, or object values, or to perform comparisons and operations on such items. RDF queries can be used by knowledge management applications as a basis for inference actions. A RDF query language is a computer language able to retrieve and manipulate data stored in Resource Description Framework format. ... Query languages are computer languages used to make queries into databases and information systems. ... Inference is the act or process of deriving a conclusion based solely on what one already knows. ...


Modeled loosely after SQL, the query language SPARQL is emerging as the de-facto RDF query language. On the track towards status of W3C Recommendation, it was released as a Candidate Recommendation in April 2006, but is back to Working Draft status since October 2006, due to open issues. SQL (commonly expanded to Structured Query Language — see History for the terms derivation) is the most popular computer language used to create, retrieve, update and delete (see also: CRUD) data from relational database management systems. ... SPARQL (recursively, SPARQL Protocol and RDF Query Language) is a Semantic Web recommendation presently (as of 2005) undergoing standardization by the RDF Data Access Working Group (DAWG) of the World Wide Web Consortium. ... A W3C Recommendation is the final stage of a ratification process of the W3C working group concerning the standard. ...


Other notable RDF query and inference languages include:

  • RDQL, precursor to SPARQL, SQL-like
  • Versa, compact syntax (non–SQL-like), solely implemented in 4Suite (Python)
  • XUL has a template element in which to declare rules for matching data in RDF. XUL uses RDF extensively for databinding.

A RDF query language is a computer language able to retrieve and manipulate data stored in Resource Description Framework format. ... SPARQL (recursively, SPARQL Protocol and RDF Query Language) is a Semantic Web recommendation presently (as of 2005) undergoing standardization by the RDF Data Access Working Group (DAWG) of the World Wide Web Consortium. ... In computing, Versa is a query language for RDF data. ... Python is a high-level programming language first released by Guido van Rossum in 1991. ... XUL (pronounced zool ()), the XML User Interface Language, is an XML user interface markup language developed by the Mozilla project. ... XUL (pronounced zool ()), the XML User Interface Language, is an XML user interface markup language developed by the Mozilla project. ...

Applications

  • 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 content.
  • FOAF (Friend of a Friend) - designed to describe people, their interests and interconnections.
  • DOAC (Description of a Career) - supplements FOAF to allow the sharing of résumé information.
  • DOAP (Description of a Project) - designed to describe software projects; uses FOAF to identify the people involved
  • 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. See [6]
  • MusicBrainz - Publishes information about Music Albums. See [7].
  • Creative Commons - Uses RDF to embed license information in web pages and mp3 files.
  • Haystack - Semantic web browser from MIT CS & AI lab. See - [8]
  • Many other RDF schemas are available by searching SchemaWeb
  • Microsoft shipped a product Connected Services Framework which provides an RDF based Profile Management capabilities.

For RSS feeds from Wikipedia, see Wikipedia:Syndication. ... A weblog (now more commonly known as a blog) is a web-based publication consisting primarily of periodic articles (normally, but not always, in reverse chronological order). ... FOAF (Friend of a Friend) is a project for machine-readable modelling of homepage-like content and social networks founded by Libby Miller and Dan Brickley. ... Interest is the rent paid to borrow money. ... Description Of A Career (DOAC) is a semantic vocabulary created by Ramon A. Parada to describe professional capabilities of a worker. ... This article or section does not adequately cite its references or sources. ... For the british film, see Death of a President DOAP (Description Of A Project) is an attempt to make an RDF schema and XML vocabulary to describe open-source projects. ... Semantically-Interlinked Online Communities Project (SIOC) is a Semantic Web technology. ... MusicBrainz (MusicBrainz. ... The Creative Commons (CC) is a non-profit organization devoted to expanding the range of creative work available for others legally to build upon and share. ...

See also

The semantic web is an evolving extension of the World Wide Web in which web content can be expressed not only in natural language, but also in a form that can be understood, interpreted and used by software agents, thus permitting them to find, share and integrate information more easily. ... RDF Schema is a language for describing vocabularies in RDF. RDF Schema is a semantic extension of RDF. It provides mechanisms for describing groups of related resources and the relationships between these resources. ... RDFa is a set of extensions to XHTML being proposed by W3C. RDFa uses attributes from XHTMLs meta and link elements, and generalises them so that they are usable on all elements. ... Meta Content Framework (MCF) was a specification of a format for structuring metadata information about web sites and other data. ... The Web Ontology Language (OWL) is a language for defining and instantiating Web ontologies. ... This article, image, template or category should belong in one or more categories. ... Topic Maps are an ISO standard for the representation and interchange of knowledge, with an emphasis on the findability of information. ... A pictorial representation of a graph In mathematics and computer science, graph theory is the study of graphs, mathematical structures used to model pairwise relations between objects from a certain collection. ... Life Science Identifiers are a uniform way to name and locate pieces of information on the web. ... In machine translation, Universal Networking Language (UNL) is an artificial pivot language, that relies on the semi-automatic translation from the initial text in a natural language into its pivot equivalent. ... A tag is a (relevant) keyword or term associated with or assigned to a piece of information (like picture, article, or video clip), thus describing the item and enabling keyword-based classification of information it is applied to. ... A folksonomy is a user generated taxonomy used to categorize and retrieve Web pages, photographs, Web links and other web content using open ended labels called tags. ...

External links

News and resources

Tutorials and documents

RDF software tools

This article or section does not adequately cite its references or sources. ... Drag-and-drop refers to the act of (or support for the act of) clicking on a virtual object and dragging it to, or onto, another virtual object. ...

RDF datasources


  Results from FactBites:
 
Resource Description Framework: Information from Answers.com (1746 words)
Resource Description Framework (RDF) is a family of World Wide Web Consortium (W3C) specifications originally designed as a metadata model using XML but which has come to be used as a general method of modeling knowledge, through a variety of syntax formats (XML and non-XML).
One way to represent the fact "The sky has the colour blue" in RDF would be as a triple whose subject is "the sky," whose predicate is "has the color", and whose object is "blue." Predicates are traits or aspects about a resource and express a relationship between the subject and the object.
RDF query languages allow expressions to be written that can be evaluated against a collection of statements in order to produce, for example, a narrowed set of statements, resources, or object values, or to perform comparisons and operations on such items.
Resource Description Framework (RDF) Schema Specification (5684 words)
RDF and the RDF Schema language were also based on metadata research in the the Digital Library community.
RDF represents an evolution of the Warwick Framework model in that the Warwick Framework allowed each metadata vocabulary to be represented in a different syntax.
This indicates that a resource is a member of a class, and thus has all the characteristics that are to be expected of a member of that class.
  More results at FactBites »

 
 

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