Resource Description Framework

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Resource Description Framework

The Resource Description Framework (RDF) is a family of World Wide Web Consortium

World Wide Web Consortium

The World Wide Web Consortium is the main international standards organization for the World Wide Web . It is arranged as a consortium where member organizations maintain full-time staff for the purpose of working together in the development of standards for the World Wide Web....
(W3C) specifications originally designed as a metadata

Metadata

Metadata is "data about other data", of any sort in any media. An item of metadata may describe an individual datum, or content item, or a collection of data including multiple content items and hierarchical levels, for example a database schema....
data model

Data model

A data model in software engineering is an abstract model that describes how Data is represented and accessed. Data models formally define data elements and relationships among data elements for a domain of interest....
. It has come to be used as a general method for conceptual description or modeling, of information that is implemented in web resources; using a variety of syntax formats.

cally speaking, the RDF data model is not different from classic conceptual modeling approaches such as Entity-Relationship

Entity-relationship model

An Entity-Relationship Model in software engineering is an abstract and conceptual representation of data. Entity-relationship modeling is a relational schema database modeling method, used to produce a type of conceptual schema or semantic data model of a system, often a relational database, and its requirements in a top-down fashion....
or Class diagram

Class diagram

In software engineering, a class diagram in the Unified Modeling Language , is a type of static structure diagram that describes the structure of a system by showing the system's class es, their attributes, and the Object-oriented programming between the classes....
s, as it is based upon the idea of making statement

Statement

Statement may refer to:*News release, a statement issued to the news media*statement that is either true or false*Sentence , a type of sentence...
s about resources, in particular, Web resource

Resource (Web)

The concept of resource is primitive in the World Wide Web architecture, and is used in the definition of its fundamental elements. The term was first introduced to refer to targets of Uniform Resource Locators , but its definition has been further extended to include the referent of any Uniform Resource Identifier , or Internationalized Reso...
s, in the form of subject-predicate-object expressions.

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Encyclopedia

The Resource Description Framework (RDF) is a family of World Wide Web Consortium

World Wide Web Consortium

Metadata

Data model

Overview

Basically speaking, the RDF data model is not different from classic conceptual modeling approaches such as Entity-Relationship

Entity-relationship model

Class diagram

Statement

Statement may refer to:*News release, a statement issued to the news media*statement that is either true or false*Sentence , a type of sentence...
s about resources, in particular, Web resource

Resource (Web)

Aspect

Aspect may be:*Aspect , a feature that is linked to many parts of a program, but which is not necessarily the primary function of the program...
s of the resource and expresses a relationship between the subject and the object. For example, one way to represent the notion "The sky has the color blue" in RDF is as the triple: a subject

Subject (grammar)

The subject is one of the two main constituent every sentence can be divided into, according to a tradition that can be tracked back to Aristotle....
denoting "the sky", a predicate

Predicate (grammar)

In traditional grammar, a predicate is one of the two main parts of a sentence . In current semantics, a predicate is an expression that can be true of something....
denoting "has the color", and an object

Object (grammar)

An object in grammar is a sentence element and part of the sentence Predicate . It denotes somebody or something involved in the subject's "performance" of the verb....
denoting "blue". RDF is an abstract model with several serialization formats

Serialization

In computer science, in the context of data storage and transmission, serialization is the process of converting an object into a sequence of bits so that it can be stored on a storage medium or transmitted across a computer network connection link....
(i.e., file formats), and so the particular way in which a resource or triple is encoded varies from format to format.

This mechanism for describing resources is a major component in what is proposed by the W3C's Semantic Web

Semantic Web

The Semantic Web is an evolving extension of the World Wide Web in which the semantics of information and services on the web is defined, making it possible for the web to understand and satisfy the requests of people and machines to use the web content....
activity: an evolutionary stage of the World Wide Web

World Wide Web

The World Wide Web is a very large set of interlinked hypertext documents accessed via the Internet. With a Web browser, one can view Web pages that may contain writing, s, videos, and other multimedia and navigate between them using hyperlinks....
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

Certainty can be defined as either perfect knowledge that has total security from error, or the mental state of being without doubt. Objectively defined, certainty is total continuity and validity of all foundationalism inquiry, to the highest degree of precision....
. RDF's simple data model and ability to model disparate, abstract concepts has also led to its increasing use in knowledge management

Knowledge management

Knowledge Management comprises a range of Best practice used in an organisation to identify, create, represent, distribute and enable adoption of insights and experiences....
applications unrelated to Semantic Web activity.

A collection of RDF statements intrinsically represents a labeled, directed multi-graph

Glossary of graph theory

Graph theory is a growing area in mathematical research, and has a large specialized vocabulary. Some authors use the same word with different meanings....
. As such, an RDF-based data model

Data model

Knowledge representation

Knowledge representation is an area in artificial intelligence that is concerned with how to formally "think", that is, how to use a symbol system to represent "a domain of discourse" - that which can be talked about, along with functions that may or may not be within the domain of discourse that allow inference about the objects within the...
than the relational model

Relational model

The relational model for database management is a database model based on first-order logic, first formulated and proposed in 1969 by Edgar F. Codd....
and other ontological

Ontology (computer science)

In computer science and information science, an ontology is a formal representation of a set of concepts within a Domain of discourse and the relationships between those concepts....
models traditionally used in computing today. However, in practice, RDF data is often persisted in relational database or native representations also called Triple stores, or Quad stores if context (i.e. the named graph) is also persisted for each RDF triple. As RDFS and OWL

Web Ontology Language

The Web Ontology Language is a family of knowledge representation languages for authoring Ontology , and is endorsed by the World Wide Web Consortium....
demonstrate, additional ontology languages can be built upon RDF.

History

There were several ancestors to the W3C's RDF. Technically the closest was MCF

Meta Content Framework

Meta Content Framework was a specification of a format for structuring metadata about web sites and other data. MCF was developed by Ramanathan V....
, a project initiated by Ramanathan V. Guha

Ramanathan V. Guha

Ramanathan V. Guha is an Indian Computer science. He graduated from Indian Institute of Technology Madras. Since May 2005, he has been working at Google....
while at Apple Computer

Apple Computer

Apple Inc., formerly Apple Computer Inc., is an United States multinational corporation which designs and manufactures consumer electronics and software products....
and continued, with contributions from Tim Bray

Tim Bray

Timothy William Bray is a Canadian software developer and entrepreneur. He co-founded Open Text Corporation and Antarctica Systems. Currently, Tim is the Director of Web Technologies at Sun Microsystems....
, during his tenure at Netscape Communications Corporation. Ideas from the Dublin Core

Dublin Core

Platform for Internet Content Selection

The Platform for Internet Content Selection is a specification created by W3C that uses Metadata to label webpages to help parents and teachers control what children and students can access on the Internet....
, the Platform for Internet Content Selection (the W3C's early Web content labelling system) were also key in shaping the direction of the RDF project.

The W3C published a specification of 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 technologies of the W3C. Most newcomers to RDF are unaware that the older specifications even exist.

RDF Topics

Serialization formats

Two common serialization formats

Serialization

In computer science, in the context of data storage and transmission, serialization is the process of converting an object into a sequence of bits so that it can be stored on a storage medium or transmitted across a computer network connection link....
are in use.

The first is an XML format. This format is often called simply RDF because it was introduced among the other W3C specifications defining RDF. However, it is important to distinguish the XML format from the abstract RDF model itself. Its MIME

MIME

Multipurpose Internet Mail Extensions is an Internet standard that extends the format of electronic mail to support:* Text in character sets other than ASCII...
media type, application/rdf+xml, was registered by RFC 3870. It recommends RDF documents to follow the new 2004 specifications.

In addition to serializing RDF as XML, the W3C introduced Notation 3

Notation 3

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....
(or N3) as a non-XML serialization of RDF models designed to be easier to write by hand, and in some cases easier to follow. Because it is based on a tabular notation, it makes the underlying triples encoded in the documents more easily recognizable compared to the XML serialization. N3 is closely related to the Turtle

Turtle (syntax)

Turtle is a serialisation format for Resource Description Framework graphs. A subset of Tim Berners-Lee and Dan Connolly's Notation 3 language, it was defined by Dave Beckett , and is a superset of the minimal N-Triples format....
and N-Triples

N-Triples

N-Triples is a line-based, plain text serialisation format for Resource Description Framework graphs. It is a subset of the Turtle format. N-Triples should not be confused with Notation 3 which is a superset of Turtle....
formats.

Triples may be stored in a triplestore

Triplestore

A triplestore is a purpose-built database for the storage and retrieval of Resource Description Framework metadata.Much like a relational database, one stores information in a triplestore and retrieves it via a query language....
.

Resource identification

The subject of an RDF statement is a resource

Resource (Web)

The concept of resource is primitive in the World Wide Web architecture, and is used in the definition of its fundamental elements. The term was first introduced to refer to targets of Uniform Resource Locators , but its definition has been further extended to include the referent of any Uniform Resource Identifier , or Internationalized Reso...
, possibly as named by a Uniform Resource Identifier

Uniform Resource Identifier

In Information technology, a Uniform Resource Identifier is a Character string of Character s used to Identifier or name a Resource on the Internet....
(URI). Some resources are unnamed and are called blank node

Blank node

In Resource Description Framework, a blank node is a Resource , or node in an RDF graph, which is not identified by a URI. A blank node can be used as subject or object in an RDF triple....
s 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

Unicode

Unicode is a computing industry standard allowing computers to consistently represent and manipulate Character expressed in most of the world's writing systems....
string literal

String literal

A string literal is the representation of a String value within the source code of a computer program. There are numerous alternate notations for specifying string literals, and the exact notation depends on the individual programming language in question....
.

In Semantic Web applications, and in relatively popular applications of RDF like RSS

RSS (file format)

RSS is a family of Web feed formats used to publish frequently updated works?such as blog entries, news headlines, audio, and video?in a standardized format....
and FOAF

FOAF (software)

FOAF is a machine-readable Ontology describing persons, their activities and their relations to other people and objects. Anyone can use FOAF to describe him or herself....
(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 represent absolutely anything (as a fanciful example, the URI could even represent the abstract notion of world peace

World peace

World peace is an ideal of Freedom , peace, and happiness among and within all nations and/or peoples. It is the professed ambition of many past and present world leaders....
).

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

Dublin Core

Statement reification and context

The body of knowledge modeled by a collection of statements may be subjected to reification

Reification (knowledge representation)

Reification in knowledge representation is sometimes used to represent facts that must then be manipulated in some way; for example, to compare logical assertions from different witnesses to determine their credibility....
, 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

Logic is the study of the principles of valid demonstration and inference. Logic is a branch of philosophy, a part of the classical Trivium . The word derives from Greek language ?????? , fem....
(and as illustrated in graphical notations such as conceptual graphs and topic map

Topic map

Topic Maps is a standard for the representation and interchange of knowledge, with an emphasis on the findability of information. The International Organization for Standardization standard is formally known as ISO/IEC 13250:2003....
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.

In first-order logic

First-order logic

First-order logic is a formal deductive system used in mathematics, philosophy, linguistics, and computer science. It goes by many names, including: first-order predicate calculus , the lower predicate calculus, the language of first-order logic or predicate logic....
, as facilitated by RDF without scopes, the only metalevel relation is negation

Negation

In logic and mathematics, negation or not is an operation on logical values, for example, the logical value of a proposition, that sends true to false and false to true....
, 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

Higher-order logic

In mathematics, higher-order logic is distinguished from first-order logic in a number of ways.One of these is the type of Free variables and bound variables appearing in quantifications; in first-order logic, roughly speaking, it is forbidden to quantify over Predicate s....
.

Query and inference languages

The predominant query language for RDF graphs is SPARQL

SPARQL

SPARQL is an RDF query language; its name is a recursive acronym that stands for SPARQL Protocol and RDF Query Language....
. SPARQL is an SQL

SQL

SQL is a database computer language designed for the retrieval and management of data in relational database management systems , database schema creation and modification, and database object access control management....
-like language, and a recommendation

W3C recommendation

A W3C Recommendation is the final stage of a ratification process of the World Wide Web Consortium working group concerning the standard. This designation signifies that a document has been subjected to a public and W3C-member organization's review....
of the W3C as of January 15, 2008.

An example of a SPARQL query to show country capitals in Africa, using a fictional ontology.

PREFIX abc:  .
SELECT ?capital ?country
WHERE

Other ways to query RDF graphs

RDF query language

An RDF query language is a computer language able to retrieve and manipulate data stored in Resource Description Framework format.SPARQL is emerging as the de-facto RDF query language, and is a W3C Recommendation....
include:

RDQL, precursor to SPARQL
SPARQL

SPARQL is an RDF query language; its name is a recursive acronym that stands for SPARQL Protocol and RDF Query Language....
, SQL-like
Versa, compact syntax (non–SQL-like), solely implemented in 4Suite (Python
Python (programming language)

Python is a general-purpose high-level programming language. Its design philosophy emphasizes code readability. Python's core syntax and semantics are Minimalism , while the standard library is large and comprehensive....
)
RQL, one the first declarative languages for uniformly querying RDF schemas and resource descriptions, implemented in RDFSuite.
XUL
XUL

XUL , the XML User Interface Language, is an XML user interface markup language developed by the Mozilla project which operates in Mozilla cross-platform applications such as Mozilla Firefox and Flock ....
has a element in which to declare rules for matching data in RDF. XUL
XUL

XUL , the XML User Interface Language, is an XML user interface markup language developed by the Mozilla project which operates in Mozilla cross-platform applications such as Mozilla Firefox and Flock ....
uses RDF extensively for databinding.

Examples

Example 1: The postal abbreviation for New York

Certain concepts in RDF are taken from logic

Logic

Linguistics

Linguistics is the science study of natural language. Linguistics encompasses a number of sub-fields. An important topical division is between the study of language structure and the study of Meaning ....
, 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 language

English is a West Germanic language that originated in Anglo-Saxon England and has lingua franca status in many parts of the world as a result of the military, economic, scientific, political and cultural influence of the British Empire in the 18th, 19th and early 20th centuries and that of the United States from the mid 20th century onwa...
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 Notation 3

Notation 3

"NY" .

In this example, "urn:x-states:New%20York" is the URI for a resource that denotes the U.S. state New York

New York

The State of New York is a U.S. state in the Mid-Atlantic States and Northeastern United States regions of the United States and is the nation's List of U.S....
, "http://purl.org/dc/terms/alternative" is the URI for a predicate (whose human-readable definition can be found at ), 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.

N-Triples is just one of several standard serialization

Serialization

In computer science, in the context of data storage and transmission, serialization is the process of converting an object into a sequence of bits so that it can be stored on a storage medium or transmitted across a computer network connection link....
formats for RDF. The triple above can also be equivalently represented in the standard RDF/XML format as:

NY

However, because of the restrictions on the syntax of QName

QName

QNames were introduced by XML Namespaces in order to be used as Uniform Resource Identifier references. QName stands for "qualified name" and defines a valid identifier for elements and attributes....
s (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

Wikipedia

Wikipedia is a Free content, multilingualism encyclopedia project supported by the non-profit organization Wikimedia Foundation. Its name is a portmanteau of the words wiki and encyclopedia....
article about Tony Benn

Tony Benn

Anthony "Tony" Neil Wedgwood Benn , formerly 2nd Viscount Stansgate, is a United Kingdom socialist politician and the current President of the Stop the War Coalition....
), 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" .

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

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

Semantics encoding

A semantics encoding is a "translation" between formal languages.For programmers, the most familiar form of encoding is the compilation of a programming language into machine code or byte-code....
and interpretation mechanism so that resources

Resource (computer science)

A resource, or system resource, is any physical or virtual component of limited availability within a computer system. Every device connected to a computer system is a resource....
can be described in a way that particular software can understand it; in other words, so that software can access and use information that it otherwise couldn't use.

Both versions of the statements above are wordy because one requirement for an RDF resource (as a subject or a predicate) is that it be unique. The subject resource must be unique in an attempt to pinpoint the exact resource being described. The predicate needs to be unique in order to reduce the chance that the idea of Title

Title

A title is a Prefix or Suffix added to a person's name to signify either veneration, an official position or a professional or academic qualification....
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

Definition

A definition is a statement of the Meaning of a word or phrase. The term to be defined is known as the definiendum . The words which define it are known as the definiens ....
for the concept

Concept

A concept is a cognition unit of meaning— an abstraction idea or a mental symbol sometimes defined as a "unit of knowledge," built from other units which act as a concept's characteristics....
of a title established by the Dublin Core

Dublin Core

The Dublin Core metadata element set is a standard for cross-domain information Resource description. It provides a simple and standardised set of conventions for describing things online in ways that make them easier to find....
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 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":

Tony Benn Wikipedia Tony Benn

Applications

Creative Commons
Creative Commons

Creative Commons is a non-profit organization devoted to expanding the range of creativity works available for others to build upon legally and to share....
- Uses RDF to embed license information in web pages and mp3 files.
DOAC (Description of a Career)
Description of a Career

Description Of A Career is a semantic web vocabulary created by Ramon A. Parada to describe professional capabilities of a worker. It has been designed to be compatible with the European Union curriculum so those can be generated from a FOAF+DOAC file....
- supplements FOAF to allow the sharing of résumé
Résumé

A r?sum? is a document that contains a summary or listing of relevant job experience and education. The r?sum? or CV is typically the first item that a potential employer encounters regarding the job seeker and is typically used to screen applicants, often followed by an interview, when seeking employment....
information.
FOAF (Friend of a Friend)
FOAF (software)

FOAF is a machine-readable Ontology describing persons, their activities and their relations to other people and objects. Anyone can use FOAF to describe him or herself....
- designed to describe people
Person

The term person in common usage means an individual human being. In the fields of law, philosophy, medicine, and others, the term also has specialised context-specific meanings....
, their interest
Interest

Interest is a fee paid on borrowed assets. It is the price paid for the use of borrowed money , or, money earned by deposited funds .Assets that are sometimes lent with interest include money, shares, consumer goods through hire purchase, major assets such as aircraft finance, and even entire factories in finance lease arrangements....
s and interconnections.
Haystack client
Haystack (PIM)

Haystack is a project at the Massachusetts Institute of Technology to research and develop several Software application around personal information management and the Semantic Web....
- Semantic web browser from MIT CS & AI lab.
IDEAS Group
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....
- developing a formal 4D Ontology for Enterprise Architecture
Enterprise architecture

The term enterprise architecture refers to many things. Like architecture in general, it can refer to a description, a process or a profession....
using RDF as the encoding.
Microsoft shipped a product, Connected Services Framework ,which provides RDF-based Profile Management capabilities.
MusicBrainz
MusicBrainz

MusicBrainz is a project that aims to create an open content music database. Similar to the freedb project, it was founded in response to the restrictions placed on the CDDB....
- Publishes information about Music Albums.
NEPOMUK
NEPOMUK (framework)

NEPOMUK is an open-source software specification that is concerned with the development of a Social Semantic desktop that enriches and interconnects data from different desktop applications using semantic metadata stored as Resource Description Framework....
, 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 KDE4
KDE4

KDE 4 is the current series of releases of the KDE. The first version of this series was released on January 11 2008, and the latest version was released on March 04 2009....
desktop environment.
RDF Site Summary - one of several "RSS
RSS (file format)

RSS is a family of Web feed formats used to publish frequently updated works?such as blog entries, news headlines, audio, and video?in a standardized format....
" languages for publishing information about updates made to a web page; it is often used for disseminating news article summaries and sharing weblog content.
SIOC (Semantically-Interlinked Online Communities)
SIOC

Semantically-Interlinked Online Communities Project is a Semantic Web technology. SIOC provides methods for interconnecting discussion methods such as blogs, forums and mailing lists to each other....
- designed to describe online communities and to create connections between Internet-based discussions from message boards, weblogs and mailing lists.
Many other RDF schemas are available by searching SchemaWeb.

Criticism of RDF

RDF has been criticised in 2001 on the following grounds:

The XML syntax for RDF is too verbose.

XML-RDF is one particular representation of RDF. One example of a more grammatically concise equivalent representation is Notation 3
Notation 3

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 triple (subject, predicate, object) notation simplicity introduces reading and computation disadvantages.

The "triple" is a virtually universal linguistic construct, and has been handled by artificial langues such as PROLOG for many decades.

RDF's ability to reify statements allows for ambiguities.

RDF's ability to add an infinite amount of triples allows an author to negate ambiguity - this really is a matter of the authorship of the knowledge-representation, and not the format of the representation

External links

News and resources

: RDF datasources in Mozilla
Mozilla

Mozilla was the official, public, original name of Mozilla Application Suite by the Mozilla Foundation, currently known as SeaMonkey internet suite....

RDF software tools

Open Source semantic web tools
: freeware
Freeware

Freeware is computer software that is available for use at no cost or for an optional fee. Freeware is different from shareware; the latter obliges the user to pay ....
RDF editor and RDF browser with a drag-and-drop
Drag-and-drop

In computer graphical user interfaces, drag-and-drop or DnD is the action of clicking on a virtual object and dragging it to a different location or onto another virtual object....
interface
: tool to publish relational databases as an RDF-graph
Virtuoso Universal Server
Virtuoso Universal Server

is a middleware and database engine hybrid that combines the functionality of a traditional RDBMS, Object-relational database, virtual database, RDF, XML, free-text, Web Application Server and File Server functionality in a single server product offering....
: a SPARQL
SPARQL

SPARQL is an RDF query language; its name is a recursive acronym that stands for SPARQL Protocol and RDF Query Language....
compliant platform for RDF data management, SQL-RDF integration, and RDF based Linked Data
Linked Data

Linked Data is a term used to describe a method of exposing, sharing, and connecting data on the Semantic Web via dereferenceable URIs....
deployment
: .NET library and toolkit built to create and browse RDF documents easily. It abstracts away the level of RDF triples and elevates the level of the programming work to (OWL) classes and properties.

RDF datasources

: System One's RDF conversion of the English Wikipedia, updated monthly
DBpedia
DBpedia

DBpedia is a community effort to extract structured information from Wikipedia and to make this information available on the Web. DBpedia allows users to ask expressive queries against Wikipedia and to interlink other datasets on the Web with DBpedia data....
: a that exposes an every increasing collection of RDF based Linked Data
Linked Data

Linked Data is a term used to describe a method of exposing, sharing, and connecting data on the Semantic Web via dereferenceable URIs....
sources

Resource Description Framework

Overview

History

RDF Topics

Serialization formats

Resource identification

Statement reification and context

Query and inference languages

Examples

Example 1: The postal abbreviation for New York

Example 2: A Wikipedia article about Tony Benn

Applications

Criticism of RDF

See also

Further reading

External links