Resource Description Framework (RDF):
Concepts and Abstract Syntax

W3C Working Draft 23 January 2003

This version:
Latest version:
Previous version:
Graham Klyne (Nine by Nine), <gk@ninebynine.org>
Jeremy J. Carroll (Hewlett Packard Labs), <jjc@hpl.hp.com>
Series editor:
Brian McBride (Hewlett Packard Labs) <bwm@hplb.hpl.hp.com>


The Resource Description Framework (RDF) is a framework for representing information in the Web.

This document defines an abstract syntax on which RDF is based, and which serves to link its concrete syntax to its formal semantics. It also includes discussion of design goals, meaning of RDF documents, key concepts, datatyping, character normalization and handling of URI references.

Status of this Document

This is a W3C Last Call Working Draft of the RDF Core Working Group and has been produced as part of the W3C Semantic Web Activity (Activity Statement).

This document is in the Last Call review period, which ends on 21 February 2003. This document has been endorsed by the RDF Core Working Group.

This document is being released for review by W3C Members and other interested parties to encourage feedback and comments, especially with regard to how the changes made affect existing implementations and content.

In conformance with W3C policy requirements, known patent and IPR constraints associated with this Working Draft are detailed on the RDF Core Working Group Patent Disclosure page.

Comments on this document are invited and should be sent to the public mailing list www-rdf-comments@w3.org. An archive of comments is available at http://lists.w3.org/Archives/Public/www-rdf-comments/.

This is a public W3C Last Call Working Draft for review by W3C Members and other interested parties. This section describes the status of this document at the time of its publication. It is a draft document and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use W3C Working Drafts as reference material or to cite as other than "work in progress". A list of current W3C Recommendations and other technical documents can be found at http://www.w3.org/TR/.

Table of Contents

1. Introduction

The Resource Description Framework (RDF) is a framework for representing information in the Web.

This document defines an abstract syntax on which RDF is based, and which serves to link its concrete syntax to its formal semantics. It also includes discussion of design goals, meaning of RDF documents, key concepts, datatyping, character normalization and handling of URI references.

Normative documentation of the RDF core falls into the following areas:

Within this document, normative sections are explicitly labelled as such. Explicit notes are informative.

The framework is designed so that vocabularies can be layered on top of a core. The RDF core and RDF vocabulary definition (RDF schema) languages [RDF-VOCABULARY] are the first such vocabularies. Others (cf. OWL [OWL] and the applications in the primer [RDF-PRIMER]) are in development.

1.1 Structure of this Document

In section 2, the background rationale and design goals are introduced. Key concepts follow in section 3. The meaning of RDF is discussed in section 4, including discussion of social mechanisms, the interaction between social and formal meaning and the implications of publication of an RDF document.

RDF's abstract syntax is a graph, which can be serialized using XML (but which is quite distinct from XML's tree-based infoset [XML-INFOSET]). The abstract syntax captures the fundamental structure of RDF, independently of any concrete syntax used for serialization. The formal semantics of RDF are defined in terms of the abstract syntax. XML content of literals is described in section 5, and the abstract syntax is defined in section 6 of this document.

Section 7 discusses the role of fragment identifiers in URI references used with RDF.

2. Motivations and Goals

RDF has an abstract syntax that reflects a simple graph-based data model, and formal semantics with a rigorously defined notion of entailment providing a basis for well founded deductions in RDF data.

2.1 Motivation

The development of RDF has been motivated by the following uses, among others:

RDF is designed to represent information in a minimally constraining, flexible way. It can be used in isolated applications, where individually designed formats might be more direct and easily understood, but RDF's generality offers greater value from sharing. The value of information thus increases as it becomes accessible to more applications across the entire Internet.

2.2 Design Goals

The design of RDF is intended to meet the following goals:

2.2.1 A Simple Data Model

RDF has a simple data model that is easy for applications to process and manipulate. The data model is independent of any specific serialization syntax.

Note: the term "model" used here in "data model" has a completely different sense to its use in the term "model theory". See the RDF model theory specification [RDF-SEMANTICS] for more information about "model theory" as used in the literature of mathematics and logic.

2.2.2 Formal Semantics and Inference

RDF has a formal semantics which provides a dependable basis for reasoning about the meaning of an RDF expression. In particular, it supports rigorously defined notions of entailment which provide a basis for defining reliable rules of inference in RDF data.

2.2.3 Extensible URI-based Vocabulary

The vocabulary is fully extensible, being based on URIs with optional fragment identifiers (URI references, or URIrefs). URI references are used for naming all kinds of things in RDF.

The other kind of value that appears in RDF data is a literal.

2.2.4 XML-based Syntax

RDF has a recommended XML serialization form [RDF-SYNTAX], which can be used to encode the data model for exchange of information among applications.

2.2.5 Use XML Schema Datatypes

RDF can use values represented according to XML schema datatypes [XML-SCHEMA2], thus assisting the exchange of information between RDF and other XML applications.

2.2.6 Anyone Can Make Simple Assertions About Anything

To facilitate operation at Internet scale, RDF is an open-world framework that allows anyone to make simple assertions about anything. In general, it is not assumed that all information about any topic is available. A consequence of this is that RDF cannot prevent anyone from making assertions that are nonsensical or inconsistent with the world as people see it, and applications that build upon RDF need to find ways to deal with incomplete and conflicting sources of information. (This is where RDF departs from more prescriptive approaches to representing data in XML, which aim to present information that is well-formed and complete for an application's needs.)

2.2.7 Arbitrary Expression of Simple Facts

RDF can represent arbitrary information that can be expressed as simple facts. (What constitutes a simple fact is discussed later, in section 3.5)

2.2.8 A Basis for Binding Agreements

RDF is intended to convey assertions that are meaningful to the extent that they may, in appropriate contexts, be used to express the terms of binding agreements.

This goal is explored further in section 4.2 below.

3. RDF Concepts

RDF uses the following key concepts:

3.1 Graph Data Model

The underlying structure of any expression in RDF can be viewed as a directed labelled graph, which consists of nodes and labelled directed arcs that link pairs of nodes (these notions are defined more formally in section 6). The RDF graph is a set of triples:

image of the RDF triple comprising (subject, predicate, object)

Each property arc represents a statement of a relationship between the things denoted by the nodes that it links, having three parts:

  1. a property that describes some relationship (also called a predicate),
  2. a value that is the subject of the statement, and
  3. a value that is the object of the statement.

The direction of the arc is significant: it always points toward the object of a statement.

The meaning of an RDF graph is the conjunction (i.e. logical AND) of all the statements that it contains.

3.2 URI-based Vocabulary and Node Identification

Nodes in an RDF graph are URIs with optional fragment identifiers (URI references, or URIrefs), literals, or blank (having no separate form of identification). Arcs are labelled with URI references. (See [URI], section 4, for a description of URI reference forms, noting that relative URIs are not used in an RDF graph. See also section 6.4.)

The URI reference or literal used as a node identifies what that node represents. The label on an arc identifies the relationship between the nodes connected by the arc. The arc label may also be a node in the graph.

A blank node is an RDF graph node that is not a URI reference or a literal. In the RDF abstract syntax, a blank node is just a unique node that can be used in one or more RDF statements, and has no globally distinguishing identity.

A convention used by some linear representations of an RDF graph to allow several statements to reference the same blank node is to use a blank node identifier, which is a local identifier that can be distinguished from all URIs and literals. When graphs are merged, their blank nodes must be kept distinct if meaning is to be preserved; this may call for re-allocation of blank node identifiers.

Note that blank node identifiers are not part of the RDF abstract syntax, and the representation of statements that use blank nodes is entirely dependent on the particular concrete syntax used.

3.3 Datatypes (Normative)

Datatypes are used by RDF in the representation of values such as integers, floating point numbers and dates.

RDF uses the datatype abstraction defined by XML Schema Part 2: Datatypes [XML-SCHEMA2], and may be used with any datatype definition that conforms to this abstraction, even if not actually defined in terms of XML Schema.

A datatype mapping is a set of pairs whose first element belongs to the lexical space of the datatype, and the second element belongs to the value space of the datatype:

With one exception, the datatypes used in RDF have a lexical space consisting of a set of strings. The exception is rdf:XMLLiteral, whose lexical space also includes pairs of strings and language identifiers. The value obtained through its datatype mapping may depend on the language identifier.

For example, the datatype mapping for the XML Schema datatype xsd:boolean, where each member of the value space (represented here as 'T' and 'F') has two lexical representations, is as follows:

Value Space {T, F}
Lexical Space {"0", "1", "true", "false"}
Datatype Mapping {<"true", T>, <"1", T>, <"0", F>, <"false", F>}

RDF predefines just one datatype rdf:XMLLiteral, used for embedding XML in RDF (see section 5).

There is no built-in concept of numbers or dates or other common values. Rather, RDF defers to datatypes that are defined separately, and identified with URI references.The predefined XML Schema datatypes [XML-SCHEMA2] are expected to be widely used for this purpose.

Certain XML Schema built-in datatypes are not suitable for use within RDF. For example, the QName datatype requires a namespace declaration to be in scope during the mapping, and is not recommended for use in RDF.

The defining authority of a URI which identifies a datatype is responsible for specifying the datatype's lexical space, value space and datatype mapping.

RDF provides no mechanism for defining new datatypes. XML Schema Datatypes [XML-SCHEMA2] provides an extensibility framework suitable for defining new datatypes for use in RDF.

3.4 Literals

Literals are used to identify values such as numbers and dates by means of a lexical representation. Anything represented by a literal could also be represented by a URI, but it is often more convenient or intuitive to use literals.

A literal may be the object of an RDF statement, but not the subject or the arc.

Literals may be plain or typed :

Continuing the example from section 3.3, the typed literals which can be defined using the XML Schema datatype xsd:boolean are:

Typed Literal Datatype Mapping Value
<xsd:boolean, "true"> <"true", T> T
<xsd:boolean, "1"> <"1", T> T
<xsd:boolean, "false"> <"false", F> F
<xsd:boolean, "0"> <"0", F> F

3.5 Representation of Simple Facts

Some simple facts indicate a relationship between two objects. Such a fact may be represented as an RDF triple in which the predicate names the relationship, and the subject and object denote the two objects. A familiar representation of such a fact might be as a row in a table in a relational database. The table has two columns, corresponding to the subject and the object of the RDF triple. The name of the table corresponds to the predicate of the RDF triple. A further familiar representation may be as a two place predicate in first order logic.

Relational databases permit a table to have an arbitrary number of columns, a row of which expresses information corresponding to a predicate in first order logic with an arbitrary number of places. Such a row, or predicate, has to be decomposed for representation as RDF triples. A simple form of decomposition introduces a new blank node, corresponding to the row, and a new triple is introduced for each cell in the row. The subject of each triple is the new blank node, the predicate corresponds to the column name, and object corresponds to the value in the cell. The new blank node may also have an rdf:type property whose value corresponds to the table name.

As an example, consider Figure 5 from the [RDF-PRIMER]:

Using a Blank Node
RDF Primer Figure 5: Using a Blank Node

This information might correspond to a row in a table "STAFFADDRESSES", with a primary key STAFFID, and additional columns STREET, STATE, CITY and ZIP.

Thus, a more complex fact is expressed in RDF using a conjunction (logical-AND) of simple binary relationships. RDF does not provide means to express negation (NOT) or disjunction (OR). The expressive power of RDF corresponds to the existential-conjunctive (EC) subset of first order logic [Sowa].

Through its use of extensible URI-based vocabularies, RDF provides for expression of facts about arbitrary subjects; i.e. assertions of named properties about specific named things. A URI can be constructed for any thing that can be named, so RDF facts can be about any such things.

3.6 Entailment

The ideas on meaning and inference in RDF are underpinned by the formal concept of entailment, as discussed in the RDF semantics document [RDF-SEMANTICS]. In brief, an RDF expression A is said to entail another RDF expression B if every possible arrangement of things in the world that makes A true also makes B true. On this basis, if the truth of A is presumed or demonstrated then the truth of B can be inferred .

3.7 RDF Core URI Vocabulary and Namespaces (Normative)

RDF uses URIs to identify resources and properties. Certain URIs are reserved for use by RDF, and may not be used for any purpose not sanctioned the RDF specifications. Specifically, URIs with the following leading substrings are reserved for RDF core vocabulary:

Used with the RDF/XML serialization, these URI prefix strings correspond to XML namespaces [XML-NS] associated with the RDF core vocabulary terms.

Note: these namespace URIs are the same as those used in earlier RDF documents [RDF-MS] [RDF-SCHEMA].

[[[NOTE FOR REVIEWERS: Some terms in these namespaces have been deprecated, some have been added, and some RDF schema terms have had their meaning changed. We invite community feedback regarding the relative costs of adopting these changes under the old namespace URIs vs creating new URIs for this revision of RDF.]]]

Vocabulary terms in the rdf: namespace are listed in section 5.1 of the RDF syntax specification [RDF-SYNTAX].

Vocabulary terms defined in the rdfs: namespace are defined in the RDF schema vocabulary specification [RDF-VOCABULARY].

4. Meaning of RDF (Normative)

There are two aspects to the meaning of an RDF graph. There is the formal meaning as determined by the RDF semantics [RDF-SEMANTICS]. This determines, with mathematical precision, the conclusions that can logically be drawn from an RDF graph. There is also the social meaning of the graph. It is the social meaning that affects what it means to people and how it interacts with human social institutions such as our systems of law.

4.1 Asserted and Non-asserted Forms

RDF/XML expressions, i.e. encodings of RDF graphs, can be used to make claims or assertions about the 'real' world. Such expressions are said to be asserted.

Not every RDF/XML expression is asserted. Some may convey meaning that is partly determined by the circumstances in which they are used. For example, in English, a statement "I don't believe that George is a clown" contains the words "George is a clown", which, considered in isolation, has the form of an assertion that George exhibits certain comic qualities. However, considering the whole sentence, no such assertion is considered to be made.

4.2 Social Meaning

When an RDF graph is asserted in the Web, its publisher is saying something about their view of the world. Such an assertion should be understood to carry the same social import and responsibilities as an assertion in any other format. A combination of social (e.g. legal) and technical machinery (protocols, file formats, publication frameworks) provide the contexts that fix the intended meanings of the vocabulary of some piece of RDF, and which distinguish assertions from other uses (e.g. citations, denials or illustrations).

The technical machinery includes protocols for transferring information (e.g. HTTP, SMTP) and file formats for encapsulating and labelling information (e.g. MIME, XML). A media type, application/rdf+xml [RDF-MIME-TYPE] indicates the use of RDF/XML as distinct from some other XML that happens to look like RDF. Issuing an HTTP GET request and obtaining data with a "200 OK" response code is a technical indication that the received data was published at the request URI; but data received with a "404 Not found" response cannot be considered to be similarly published information.

The social machinery includes the form of publication: publishing some unqualified statements on one's World Wide Web home page would generally be taken as an assertion of those statements. But publishing the same statements with a qualification, such as "here are some common myths", or as part of a rebuttal, would likely not be construed as an assertion of the truth of those statements. Similar considerations apply to the publication of assertions expressed in RDF.

An RDF graph may contain "defining information" that is opaque to logical reasoners. This information may be used by human interpreters of RDF information, or programmers writing software to perform specialized forms of deduction in the Semantic Web.

4.3 Authoritative Definition of Terms

The social conventions surrounding use of RDF assume that any RDF URI reference gains its meaning from some defining individual, organization or context. This applies most notably to RDF predicate URI references.

These social conventions are rooted in the URI specification [URI] and registration procedures [URI-REG]. A URI scheme registration refers to a specification of the detailed syntax and interpretation for that scheme, from which the defining authority for a given URI may be deduced. In the case of http: URIs, the defining specification is the HTTP protocol specification [HTTP], which specifies how to use the HTTP protocol to obtain a resource representation from the host named in the URI; thus, the owner of the indicated DNS domain controls (observable aspects of) the URI's meaning.

Thus, the choice of terms used in published RDF is significant in determining its meaning, through reference to definitions asserted by the defining authorities for those terms.

For important documents, the use of third-party vocabulary should be restricted to terms defined by trustworthy parties (e.g. recognized standards bodies or reputable organizations), or that otherwise have socially well-established meanings.

However, even when a URI reference can be dereferenced as an RDF/XML document, it's use within an asserted RDF graph does not implicitly assert the contents of the referenced document.

4.4 Interaction Between Social and Formal Meaning

Human publishers of RDF content commit themselves to the mechanically-inferred social obligations.

The meaning of an RDF document includes the social meaning, the formal meaning, and the social meaning of the formal entailments. The assertion of an RDF graph G, when G logically entails G', includes the implicit assertion of G'. The implied assertion of G' should be interpreted using the same social conventions that are reasonably used to interpret the assertion of G.

4.5 Example (Informative)

Imagine two websites publishing the following RDF:

(A) http://insult.example.com/lexicon#
asserts the following, and this is all that one can find on the website about that term:
A:Clown rdf:type rdfs:Class .
A:Clown rdfs:comment "A class of foolish people, whose pronouncements are probably ill-considered and not to be taken seriously" .

(B) http://AngloSaxon.example.org/lexicon#
B:Comic rdf:subClassOf <http://insult.example.com/lexicon#Clown> .

Imagine also a third, using the vocabulary previously defined by the first two.

(C) http://skunk.example.org/
asserts the following, assuming that C:JohnSmith is understood to refer to some particular person:

C:JohnSmith rdf:type <http://AngloSaxon.example.org/lexicon#Comic> .

Now, it follows by the formal RDF model theory that these three together entail:

C:JohnSmith rdf:type A:Clown .
<A:Clown> rdfs:comment "A class of foolish people, whose pronouncements are probably ill-considered and not to be taken seriously" .

Given this formal entailment, the social context of rdfs:comment is understood by referring to the [RDF-VOCABULARY] which says it provides: "a human-readable description of a resource". Thus, the person identified as C:JohnSmith might reasonably consider himself to be insulted.

Moreover, since the publishers of the third Web site http://skunk.example.org/ link C:JohnSmith to the vocabulary previously defined to be insulting, it is they who have insulted C:JohnSmith.

5. XML Content within an RDF Graph (Normative)

RDF provides for XML content as a possible literal value. This typically originates from the use of rdf:parseType="Literal" in the RDF/XML Syntax [RDF-SYNTAX].

Such content is indicated in an RDF graph using a typed literal whose datatype is a special built-in datatype, rdf:XMLLiteral.

As part of the definition of this datatype, an ancillary definition is used.

The XML document corresponding to a pair ( str, lang ) is formed as follows:

Concatenate the five strings:

  1. "<rdf-wrapper xml:lang='"
  2. lang
  3. "'>"
  4. str
  5. "</rdf-wrapper>"

Encode the resulting Unicode string in UTF-8 to form the corresponding XML document.

No escaping is applied. The choice of rdf-wrapper is fixed but arbitrary.

The XML document corresponding to a string str is formed as the XML document corresponding to the pair (str, "").

Using this, the datatype rdf:XMLLiteral is defined as follows.

The datatype URI
is http://www.w3.org/1999/02/22-rdf-syntax-ns#XMLLiteral.
The value space
is the set of all XML documents that:
The lexical space
contains all pairs ( string, lang ) where lang is any language identifier [RFC-3066] in lowercase, and string is well-balanced, self-contained XML element content [XML], for which the XML document corresponding to the pair is a well-formed XML document [XML] that also conforms to XML Namespaces [XML-NS].
also contains all strings string which are well-balanced, self-contained XML element content [XML], and for which the corresponding XML document is a well-formed XML document [XML] that also conforms to XML Namespaces [XML-NS].
The mapping
is defined as the function that maps a pair or string to the canonical form [XML-C14N] (with comments) of the corresponding XML document.

Reminder: All other datatypes have a lexical space being a set of strings, and a mapping which maps strings to values.

Note: Not all values of this datatype are compliant with XML 1.1 [XML 1.1]. If compliance with XML 1.1 is desired, then only those values that are fully normalized according to XML 1.1 should be used.

6. Abstract Syntax (Normative)

This section defines the RDF abstract syntax. The RDF abstract syntax is a set of triples, called the RDF graph.

This section also defines equality between RDF graphs. A definition of equality is needed to support the RDF Test Cases [RDF-TESTS] specification.

6.1 RDF Triples

An RDF triple contains three components:

An RDF triple is conventionally written in the order subject, predicate, object.

The predicate is also known as the property of the triple.

6.2 RDF Graph

An RDF graph is a set of RDF triples.

The nodes of an RDF graph is the set of subjects and objects of triples in the graph.

6.3 Graph Equality

Two RDF graphs G and G' are equal if there is a bijection M between the nodes of the two graphs, such that:

  1. M(lit)=lit for all RDF literals lit which are nodes of either graph.
  2. M(uri)=uri for all RDF URI references uri which are nodes of either graph.
  3. The triple ( s, p, o ) is in G if and only if the triple ( M(s), p, M(o) ) is in G'

With this definition, there are the same number of blank nodes in the two graphs, and M shows how each blank node in G can be replaced with a new blank node to give G'.

6.4 RDF URI References

A URI reference within an RDF graph (an RDF URI reference) is a Unicode string [UNICODE] that:

The encoding consists of:

  1. encoding the Unicode string as UTF-8 [RFC-2279], giving a sequence of octet values.
  2. %-escaping octets that do not correspond to permitted US-ASCII characters.

The disallowed octets that must be %-escaped include all those that do not correspond to US-ASCII characters, and the excluded characters listed in Section 2.4 of [URI], except for the number sign (#), percent sign (%), and the square bracket characters re-allowed in [RFC-2732].

Disallowed octets must be escaped with the URI escaping mechanism (that is, converted to %HH, where HH is the 2-digit hexadecimal numeral corresponding to the octet value).

Two RDF URI references are equal if and only if they compare as equal, character by character, as Unicode strings.

Editors' Note: This section is in the scope of the TAG issue IRIEverywhere-27. The editors are expecting a resolution of this issue during the last call period. This may result in updates to this section.

Note: RDF URI references are compatible with the anyURI datatype as defined by XML schema datatypes [XML-SCHEMA2], constrained to be an absolute rather than a relative URI reference, and constrained to be in Unicode Normal Form C [NFC] (for compatibility with [CHARMOD]).

Note: RDF URI references are compatible with International Resource Identifiers as defined by [XML Namespaces 1.1].

Note: The restriction to absolute URI references is found in this abstract syntax. When there is a well-defined base URI, concrete syntaxes, such as RDF/XML, may permit relative URIs as a shorthand for such absolute URI references.

6.5 RDF Literals

A literal in an RDF graph contains three components called:

The lexical form is present in all RDF literals; the language identifier and the datatype URI may be absent from an RDF literal.

A plain literal is one in which the datatype URI is absent.

A typed literal is one in which the datatype URI is present.

Note: Literals in which the lexical form begins with a composing character (as defined by [CHARMOD]) are allowed however they may cause interoperability problems, particularly with XML version 1.1 [XML 1.1].

Note: When using the language identifier, care must be taken not to confuse language with locale. The language identifier only relates to human language text. Presentational issues, how to best represent typed data to the end-user, should be addressed in end-user applications.

6.5.1 Literal Equality

Two literals are equal if and only if all of the following hold:

Note: RDF Literals are distinct and distinguishable from RDF URI references; e.g. http://example.org as an RDF Literal (untyped, without a language identifier) is not equal to http://example.org as an RDF URI reference.

6.5.2 The Value Corresponding to a Typed Literal

The datatype URI refers to a datatype. For XML Schema built-in datatypes, URIs such as http://www.w3.org/2001/XMLSchema#int are used. The URI of the datatype rdf:XMLLiteral may be used. There may be other, implementation dependent, mechanisms by which URIs refer to datatypes.

The value associated with a typed literal is found by applying the datatype mapping associated with the datatype URI to the lexical form. Exceptionally, if the datatype is rdf:XMLLiteral and the literal has a language identifier, then the datatype mapping is applied to the pair form by the lexical form and the language identifier.

If the lexical form is not in the lexical space of the datatype associated with the datatype URI, then no literal value can be associated with the typed literal. Such a case, while in error, is not syntacticly ill-formed.

A typed literal for which the datatype does not map the lexical form to a value is not syntacticly ill-formed.

Note: In application contexts, comparing the values of typed literals (see section 6.5.2) is usually more helpful than comparing their syntactic forms (see section 6.5.1). Similarly, for comparing RDF Graphs, semantic notions of entailment (see [RDF-SEMANTICS]) are usually more helpful than syntactic equality (see section 6.3).

6.6 Blank Nodes

The blank nodes in an RDF graph are drawn from an infinite set. This set of blank nodes, the set of all RDF URI references and the set of all literals are pairwise disjoint.

Otherwise, this set is arbitrary.

RDF makes no reference to any internal structure of blank nodes.

7. Fragment Identifiers

RDF uses an RDF URI Reference , which may include a fragment identifier, as a context free identifier for a resource. RFC 2396 [URI] states that the meaning of a fragment identifier depends on the MIME content-type of a document, i.e. is context dependent.

These apparently conflicting views are reconciled by considering that, in an RDF graph, any RDF URI reference consisting of an absolute URI and a fragment identifier identifies the same thing as the fragment identifier does in an application/rdf+xml [RDF-MIME-TYPE] representation of the resource identified by the absolute URI component. Thus:

This provides a handling of URI references and their denotation that is consistent with the RDF model theory and usage, and also with conventional Web behavior.

8. Acknowledgments

This document contains a significant contribution from Pat Hayes, Sergey Melnik and Patrick Stickler, under whose leadership was developed the framework described in the RDF family of specifications for representing datatyped values, such as integers and dates.

The editors acknowledge valuable contributions from the following: Frank Manola, Pat Hayes, Dan Brickley, Jos de Roo, Dave Beckett, Patrick Stickler, Peter F. Patel-Schneider, Jerome Euzenat, Massimo Marchiori, Tim Berners-Lee, Dave Reynolds and Dan Connolly.

Jeremy Carroll thanks Oreste Signore, his host at the W3C Office in Italy and Istituto di Scienza e Tecnologie dell'Informazione "Alessandro Faedo", part of the Consiglio Nazionale delle Ricerche, where Jeremy is a visiting researcher.

This document is a product of extended deliberations by the RDFcore Working Group, whose members have included: Art Barstow (W3C), Dave Beckett (ILRT), Dan Brickley (ILRT), Dan Connolly (W3C), Jeremy Carroll (Hewlett Packard), Ron Daniel (Interwoven Inc), Bill dehOra (InterX), Jos De Roo (AGFA), Jan Grant (ILRT), Graham Klyne (Nine by Nine), Frank Manola (MITRE Corporation), Brian McBride (Hewlett Packard), Eric Miller (W3C), Stephen Petschulat (IBM), Patrick Stickler (Nokia), Aaron Swartz (HWG), Mike Dean (BBN Technologies / Verizon), R. V. Guha (Alpiri Inc), Pat Hayes (IHMC), Sergey Melnik (Stanford University) and Martyn Horner (Profium Ltd).

This specification also draws upon an earlier RDF Model and Syntax document edited by Ora Lassilla and Ralph Swick, and RDF Schema edited by Dan Brickley and R. V. Guha. RDF and RDF Schema Working Group members who contributed to this earlier work are: Nick Arnett (Verity), Tim Berners-Lee (W3C), Tim Bray (Textuality), Dan Brickley (ILRT / University of Bristol), Walter Chang (Adobe), Sailesh Chutani (Oracle), Dan Connolly (W3C), Ron Daniel (DATAFUSION), Charles Frankston (Microsoft), Patrick Gannon (CommerceNet), R. V. Guha (Epinions, previously of Netscape Communications), Tom Hill (Apple Computer), Arthur van Hoff (Marimba), Renato Iannella (DSTC), Sandeep Jain (Oracle), Kevin Jones, (InterMind), Emiko Kezuka (Digital Vision Laboratories), Joe Lapp (webMethods Inc.), Ora Lassila (Nokia Research Center), Andrew Layman (Microsoft), Ralph LeVan (OCLC), John McCarthy (Lawrence Berkeley National Laboratory), Chris McConnell (Microsoft), Murray Maloney (Grif), Michael Mealling (Network Solutions), Norbert Mikula (DataChannel), Eric Miller (OCLC), Jim Miller (W3C, emeritus), Frank Olken (Lawrence Berkeley National Laboratory), Jean Paoli (Microsoft), Sri Raghavan (Digital/Compaq), Lisa Rein (webMethods Inc.), Paul Resnick (University of Michigan), Bill Roberts (KnowledgeCite), Tsuyoshi Sakata (Digital Vision Laboratories), Bob Schloss (IBM), Leon Shklar (Pencom Web Works), David Singer (IBM), Wei (William) Song (SISU), Neel Sundaresan (IBM), Ralph Swick (W3C), Naohiko Uramoto (IBM), Charles Wicksteed (Reuters Ltd.), Misha Wolf (Reuters Ltd.) and Lauren Wood (SoftQuad).

9. References

9.1 Normative References

RDF/XML Syntax Specification (Revised), Dave Beckett, World Wide Web Consortium, 8 November 2002 (work in progress). This version of the RDF/XML Syntax Specification (Revised) is http://www.w3.org/TR/2002/WD-rdf-syntax-grammar-20021108/. The latest version is at http://www.w3.org/TR/rdf-syntax-grammar/.
RDF Semantics, P. Hayes, World Wide Web Consortium, 12 November 2002 (work in progress). This version of the RDF Semantics is http://www.w3.org/TR/2002/WD-rdf-mt-20021112/. The latest version is at http://www.w3.org/TR/rdf-mt/.
RDF Vocabulary Description Language 1.0: RDF Schema, Dan Brickley, R.V. Guha, World Wide Web Consortium, April 2002 (work in progress). This version of the RDF Vocabulary Description Language is http://www.w3.org/TR/2002/WD-rdf-schema-20021112/. The latest version is at http://www.w3.org/TR/rdf-schema/.
Application/rdf+xml Media Type Registration, A. Swartz, IETF Internet Draft, March 2002 (work in progress). Version available at http://www.ietf.org/internet-drafts/draft-swartz-rdfcore-rdfxml-mediatype-01.txt.
Extensible Markup Language (XML) 1.0, Second Edition, T. Bray, J. Paoli, C.M. Sperberg-McQueen and E. Maler, Editors. World Wide Web Consortium. 6 October 2000. This version is http://www.w3.org/TR/2000/REC-xml-20001006. The latest version of XML is available at http://www.w3.org/TR/REC-xml.
Namespaces in XML, T. Bray, D. Hollander and A. Layman, Editors. World Wide Web Consortium. 14 January 1999. This version is http://www.w3.org/TR/1999/REC-xml-names-19990114/. The latest version of Namespaces in XML is available at http://www.w3.org/TR/REC-xml-names/.
RFC 2279 - UTF-8, a transformation format of ISO 10646, F. Yergeau, IETF, January 1998. This document is http://www.isi.edu/in-notes/rfc2279.txt.
RFC 2396 - Uniform Resource Identifiers (URI): Generic Syntax, T. Berners-Lee, R. Fielding and L. Masinter, IETF, August 1998. This document is http://www.isi.edu/in-notes/rfc2396.txt.
RFC 2616 - Hypertext Transfer Protocol -- HTTP/1.1, R. Fielding, UC Irvine, J. Gettys, J. Mogul, H. Frystyk, L. Masinter, P. Leach, T. Berners-Lee, IETF, August 1998. This document is http://www.isi.edu/in-notes/rfc2616.txt.
RFC 2717 - Registration Procedures for URL Scheme Names, R. Petke and I. King, IETF, November 1999. This document is http://www.isi.edu/in-notes/rfc2717.txt.
RFC 2732 - Format for Literal IPv6 Addresses in URL's, R. Hinden, B. Carpenter and L. Masinter, IETF, December 1999. This document is http://www.isi.edu/in-notes/rfc2732.txt.
The Unicode Standard, Version 3, The Unicode Consortium, Addison-Wesley, 2000. ISBN 0-201-61633-5, as updated from time to time by the publication of new versions. (See http://www.unicode.org/unicode/standard/versions/ for the latest version and additional information on versions of the standard and of the Unicode Character Database).
Unicode Normalization Forms, Unicode Standard Annex #15, Mark Davis, Martin Dürst. (See http://www.unicode.org/unicode/reports/tr15/ for the latest version).
RFC 3066 - Tags for the Identification of Languages, H. Alvestrand, IETF, January 2001. This document is http://www.isi.edu/in-notes/rfc3066.txt.
Canonical XML. J. Boyer. W3C Recommendation, March 2001.
Available at http://www.w3.org/TR/2001/REC-xml-c14n-20010315
Available at http://www.ietf.org/rfc/rfc3076.txt
XML Schema Part 2: Datatypes - W3C Recommendation, World Wide Web Consortium, 2 May 2001.

9.2 Informational References

RDF Test Cases, Jan Grant and Dave Beckett, Editors. Work in progress. World Wide Web Consortium, 29 April 2002. This version of the RDF Test Cases is http://www.w3.org/TR/2002/WD-rdf-testcases-20021112/. The latest version of the RDF Test Cases is at http://www.w3.org/TR/rdf-testcases/.
RDF Primer, F. Manola, E. Miller, Editors, World Wide Web Consortium W3C Working Draft, work in progress, 26 April 2002. This version of the RDF Primer is http://www.w3.org/TR/2002/WD-rdf-primer-20020426/. The latest version of the RDF Primer is at http://www.w3.org/TR/rdf-primer/.
Character Model for the World Wide Web 1.0, M. Dürst, F. Yergeau, R. Ishida, M. Wolf, A. Freytag, T Texin, Editors, World Wide Web Consortium Working Draft, work in progress, 20 February 2002. This version of the Character Model is http://www.w3.org/TR/2002/WD-charmod-20020220/. The latest version of the Character Model is at http://www.w3.org/TR/charmod/.
Extensible Markup Language (XML) 1.1, John Cowan, Editor. World Wide Web Consortium Working Draft 25 April 2002. (Work in progress)
Namespaces in XML 1.1, Tim Bray, Dave Hollander, Andrew Layman, Richard Tobin, Editors. World Wide Web Consortium Working Draft 5 September 2002. (Work in progress)
XML Information Set, John Cowan and Richard Tobin, W3C Recommendation, 24 October 2001. This document is http://www.w3.org/TR/xml-infoset/.
OWL Web Ontology Language 1.0 Reference, Mike Dean, Dan Connolly, Frank van Harmelen, James Hendler, Ian Horrocks, Deborah L. McGuinness, Peter F. Patel-Schneider, and Lynn Andrea Stein. W3C Working Draft 29 July 2002. Latest version is available at http://www.w3.org/TR/owl-ref/.
Knowledge Representation: Logical, Philosophical and Computational Foundations, John F. Sowa, Brookes/Cole, 2000. ISBN 0-534-94965-7.
Resource Description Framework (RDF) Model and Syntax Specification, O. Lassila and R. Swick, Editors. World Wide Web Consortium. 22 February 1999. This version is http://www.w3.org/TR/1999/REC-rdf-syntax-19990222/. The latest version of RDF M&S is available at http://www.w3.org/TR/REC-rdf-syntax/.
Resource Description Framework (RDF) Schema Specification 1.0, Dan Brickley and R. V. Guha, W3C Candidate Recommendation, 27 March 2000. This document is http://www.w3.org/TR/2000/CR-rdf-schema-20000327/.

RDF/XML Metadata