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RDF 1.2 XML Syntax

The Resource Description Framework (RDF) is a general-purpose language for representing information in the Web.

This document defines an XML syntax for RDF called RDF/XML in terms of Namespaces in XML, the XML Information Set [[XML-INFOSET]] and XML Base [[XMLBASE]].

RDF 1.2 XML Syntax introduces triple terms as a fourth kind of RDF term which can be used as the object of another triple, making it possible to make statements about other statements. Triple terms are typically not used explicitly as the annotation construction is generally preferred. RDF 1.2 XML Syntax also adds support for directional language-tagged strings.

This document is a part of the RDF 1.2 document suite. The document defines the RDF/XML syntax, a concrete syntax for RDF [[RDF12-CONCEPTS]].

There have been no substantive changes to this document since [[rdf-syntax-grammar]]. Minor editorial changes, if any, are detailed in .

This document defines the XML [[XML11]] syntax for RDF graphs.

This document revises the original RDF/XML grammar [[RDF-SYNTAX-GRAMMAR-19990222]] in terms of XML Information Set [[XML-INFOSET]] information items which moves away from the rather low-level details of XML, such as particular forms of empty elements. This allows the grammar to be more precisely recorded and the mapping from the XML syntax to the RDF Graph more clearly shown. The mapping to the RDF graph is done by emitting statements in the N-Triples [[RDF12-N-TRIPLES]] format.

• A document describing the basic concepts underlying RDF, as well as abstract syntax ("RDF Concepts and Abstract Syntax") [[RDF12-CONCEPTS]]
• A document describing the formal model-theoretic semantics of RDF ("RDF Semantics") [[RDF12-SEMANTICS]]
• Specifications of concrete syntaxes for RDF:
  • Turtle [[RDF12-TURTLE]] and TriG [[RDF12-TRIG]]
  • JSON-LD [[JSON-LD11]] (JSON based)
  • RDFa [[RDFA-PRIMER]] (for HTML embedding)
  • N-Triples [N-TRIPLES] and N-Quads [N-QUADS] (line-based exchange formats)
• A document describing RDF Schema [[RDF-SCHEMA]], which provides a data-modeling vocabulary for RDF data.

For a longer introduction to the RDF/XML syntax with a historical perspective, see "RDF: Understanding the Striped RDF/XML Syntax" [[STRIPEDRDF]].

This section introduces the RDF/XML syntax, describes how it encodes RDF graphs and explains this with examples. If there is any conflict between this informal description and the formal description of the syntax and grammar in sections and , the latter two sections take precedence.

The RDF Concepts and Abstract Syntax document [[RDF12-CONCEPTS]] defines the RDF data model and the RDF abstract syntax. Along with the RDF Semantics [[RDF12-SEMANTICS]] this provides an abstract syntax with a formal semantics for it. The RDF data model has nodes and labeled directed arcs that link pairs of nodes and this is represented as a set of RDF triples where each triple contains a subject node, predicate and object node. Nodes are IRIs, literals, or blank nodes. Blank nodes may be given a document-local identifier called a blank node identifier. Predicates are IRIs and can be interpreted as either a relationship between the two nodes or as defining an attribute value (object node) for some subject node.

In order to encode the graph in XML, the nodes and predicates have to be represented in XML terms — element names, attribute names, element contents and attribute values. RDF/XML uses XML QNames as defined in Namespaces in XML [[XML-NAMES]] to represent IRIs. All QNames have a namespace name which is an IRI and a short local name. In addition, QNames can either have a short prefix or be declared with the default namespace declaration and have no prefix (but still have a namespace name)

The IRI represented by a QName is determined by appending the local name part of the QName after the namespace name (IRI) part of the QName. This is used to shorten the IRI of all predicates and some nodes. IRIs identifying subject and object nodes can also be stored as XML attribute values. RDF literals which can only be object nodes, become either XML element text content or XML attribute values.

A graph can be considered a collection of paths of the form node, predicate arc, node, predicate arc, node, predicate arc, ... node which cover the entire graph. In RDF/XML these turn into sequences of elements inside elements which alternate between elements for nodes and predicate arcs. This has been called a series of node/arc stripes. The node at the start of the sequence turns into the outermost element, the next predicate arc turns into a child element, and so on. The stripes generally start at the top of an RDF/XML document and always begin with nodes.

Several RDF/XML examples are given in the following sections building up to complete RDF/XML documents. is the first complete RDF/XML document.

An RDF graph is given in where the nodes are represented as ovals which contain their IRIs where they have them, all the predicate arcs are labeled with IRIs, and string literal nodes have been written in rectangles.

If we follow one node, predicate arc ... , node path through the graph shown in :

The left-hand side of the graph corresponds to the node/predicate arc stripes:

1. Node with IRI http://www.w3.org/TR/rdf-syntax-grammar
2. Predicate Arc labeled with IRI http://example.org/terms/editor
3. Node with no IRI
4. Predicate Arc labeled with IRI http://example.org/terms/homePage
5. Node with IRI http://purl.org/net/dajobe/

In RDF/XML, the sequence of 5 nodes and predicate arcs on the left-hand side of corresponds to the usage of five XML elements of two types, for the graph nodes and predicate arcs. These are conventionally called node elements and property elements respectively. In the striping shown in , rdf:Description is the node element (used three times for the three nodes) and ex:editor and ex:homePage are the two property elements.

The graph consists of some nodes that are IRIs (and others that are not, called blank node elements) and this can be added to the RDF/XML using the rdf:about attribute on node elements to give the result in :

Adding the other two paths through the graph to the RDF/XML in gives the result in (this example fails to show that the blank node is shared between the two paths, see ):

There are several abbreviations that can be used to make common uses easier to write down. In particular, it is common that a subject node in the RDF graph has multiple outgoing predicate arcs. RDF/XML provides an abbreviation for the corresponding syntax when a node element about a resource has multiple property elements. This can be abbreviated by using multiple child property elements inside the node element describing the subject node.

Taking , there are two node elements that can take multiple property elements. The subject node with IRI http://www.w3.org/TR/rdf-syntax-grammar has property elements ex:editor and dc:title and the node element for the blank node can take ex:homePage and ex:fullName. This abbreviation gives the result shown in (this example does show that there is a single blank node):

When a predicate arc in an RDF graph points to an object node which has no further predicate arcs, which appears in RDF/XML as an empty node element <rdf:Description rdf:about="..."> </rdf:Description> (or <rdf:Description rdf:about="..." />) this form can be shortened. This is done by using the IRI of the object node as the value of an XML attribute rdf:resource on the containing property element and making the property element empty.

In this example, the property element ex:homePage contains an empty node element with the IRI http://purl.org/net/dajobe/. This can be replaced with the empty property element form giving the result shown in :

When a property element's content is string literal, it may be possible to use it as an XML attribute on the containing node element. This can be done for multiple properties on the same node element only if the property element name is not repeated (required by XML — attribute names are unique on an XML element) and any in-scope xml:lang on the property element's string literal (if any) are the same (see ) This abbreviation is known as a Property Attribute and can be applied to any node element.

This abbreviation can also be used when the property element is rdf:type and it has an rdf:resource attribute the value of which is interpreted as a IRI object node.

In :, there are two property elements with string literal content, the dc:title and ex:fullName property elements. These can be replaced with property attributes giving the result shown in :

To create a complete RDF/XML document, the serialization of the graph into XML is usually contained inside an rdf:RDF XML element which becomes the top-level XML document element. Conventionally the rdf:RDF element is also used to declare the XML namespaces that are used, although that is not required. When there is only one top-level node element inside rdf:RDF, the rdf:RDF can be omitted although any XML namespaces MUST still be declared.

The XML specification also permits an XML declaration at the top of the document with the XML version and possibly the XML content encoding. This is optional but recommended.

Completing the RDF/XML could be done for any of the correct complete graph examples from onwards but taking the smallest and adding the final components, gives a complete RDF/XML representation of the original graph in :

Description of graph (example07.rdf, output example07.nt).

It is possible to omit rdf:RDF in above since there is only one rdf:Description inside rdf:RDF but this is not shown here.

RDF/XML permits the use of the xml:lang attribute as defined by 2.12 Language Identification of XML 1.1 [[XML11]] to allow the identification of content language. The xml:lang attribute can be used on any node element or property element to indicate that the included content is in the given language. Typed literals which includes XML literals are not affected by this attribute. The most specific in-scope language present (if any) is applied to property element string literal content or property attribute values. The xml:lang="" form indicates the absence of a language identifier.

Some examples of marking content languages for RDF properties are shown in :

Complete example of xml:lang (example08.rdf, output example08.nt)

RDF 1.2 introduces the concept of a base direction which can be used to specify the initial text direction of language-tagged strings to create a directional language-tagged strings. This is specified by adding the `its:dir` attribute on any node element or property element, where `its` is the typical prefix used for the ITS namespace `http://www.w3.org/2005/11/its`. The supported values for `its:dir` are `"ltr"`, and `"rtl"` as required for directional language-tagged strings.

Some examples of marking base direction for RDF properties are shown in :

Complete example of its:dir (example09.rdf, output example09.nt)

The `its:dir` attribute is specifically tied to version 2.0 of [[ITS]], as indicated by the `its:version="2.0"` on the top-level XML document element.

RDF allows XML literals [RDF12-CONCEPTS] to be given as the object node of a predicate. These are written in RDF/XML as content of a property element (not a property attribute) and indicated using the rdf:parseType="Literal" attribute on the containing property element.

An example of writing an XML literal is given in where there is a single RDF triple with the subject node IRI http://example.org/item01, the predicate IRI http://example.org/stuff/1.0/prop (from ex:prop) and the object node with XML literal content beginning a:Box.

RDF allows typed literals to be given as the object node of a predicate. Typed literals consist of a literal string and a datatype IRI. These are written in RDF/XML using the same syntax for literal string nodes in the property element form (not property attribute) but with an additional rdf:datatype="datatypeURI" attribute on the property element. Any IRI can be used in the attribute.

An example of an RDF typed literal is given in where there is a single RDF triple with the subject node IRI http://example.org/item01, the predicate IRI http://example.org/stuff/1.0/size (from ex:size) and the object node with the typed literal ("123", http://www.w3.org/2001/XMLSchema#int) to be interpreted as an XML Schema [[XMLSCHEMA11-2]] datatype int.

Blank nodes in the RDF are distinct but have no IRI. It is sometimes required that the same blank node is referred to in the RDF/XML in multiple places, such as at the subject and object of several RDF triples. In this case, a blank node identifier can be given to the blank node for identifying it in the document. Blank node identifiers in RDF/XML are scoped to the containing XML Information Set [[XML-INFOSET]] document information item. A blank node identifier is used on a node element to replace rdf:about="IRI" or on a property element to replace rdf:resource="IRI" with rdf:nodeID="blank node identifier" in both cases.

Taking and explicitly giving a blank node identifier of abc to the blank node in it gives the result shown in . The second rdf:Description property element is about the blank node.

Blank nodes (not IRI nodes) in RDF graphs can be written in a form that allows the <rdf:Description> </rdf:Description> pair to be omitted. The omission is done by putting an rdf:parseType="Resource" attribute on the containing property element that turns the property element into a property-and-node element, which can itself have both property elements and property attributes. Property attributes and the rdf:nodeID attribute are not permitted on property-and-node elements.

Taking the earlier , the contents of the ex:editor property element could be alternatively done in this fashion to give the form shown in :

If all of the property elements on a blank node element have string literal values with the same in-scope xml:lang value (if present) and each of these property elements appears at most once and there is at most one rdf:type property element with a IRI object node, these can be abbreviated by moving them to be property attributes on the containing property element which is made an empty element.

Taking the earlier , the ex:editor property element contains a blank node element with two property elements ex:fullname and ex:homePage. ex:homePage is not suitable here since it does not have a string literal value, so it is being ignored for the purposes of this example. The abbreviated form removes the ex:fullName property element and adds a new property attribute ex:fullName with the string literal value of the deleted property element to the ex:editor property element. The blank node element becomes implicit in the now empty ex:editor property element. The result is shown in .

      <?xml version="1.0"?>
      <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
                  xmlns:dc="http://purl.org/dc/elements/1.1/"
                  xmlns:ex="http://example.org/stuff/1.0/">

        <rdf:Description rdf:about="http://www.w3.org/TR/rdf-syntax-grammar"
                  dc:title="RDF 1.2 XML Syntax">
          <ex:editor ex:fullName="Dave Beckett" />
                  <!-- Note the ex:homePage property has been ignored for this example -->
        </rdf:Description>

      </rdf:RDF>
    

It is common for RDF graphs to have rdf:type predicates from subject nodes. These are conventionally called typed nodes in the graph, or typed node elements in the RDF/XML. RDF/XML allows such triples to be expressed more concisely by replacing the rdf:Description node element name with the namespaced-element corresponding to the IRI of the value of the type relationship. There may, of course, be multiple rdf:type predicates but only one can be used in this way, the others MUST remain as property elements or property attributes.

The typed node elements are commonly used in RDF/XML with the built-in classes in the RDF Vocabulary: rdf:Seq, rdf:Bag, rdf:Alt, rdf:Statement, rdf:Property and rdf:List.

For example, the RDF/XML in 15 could be written as shown in .

RDF/XML allows further abbreviating IRIs in XML attributes in two ways. The XML Infoset provides a base URI attribute xml:base that sets the base IRI for resolving relative IRI references, otherwise the base IRI is that of the document. The base IRI applies to all RDF/XML attributes that deal with IRIs which are rdf:about, rdf:resource, rdf:ID and rdf:datatype.

The rdf:ID attribute on a node element (not on a property element; there it has another meaning) can be used instead of rdf:about and gives a relative IRI reference equivalent to # concatenated with the rdf:ID attribute value. So for example if rdf:ID="name", that would be equivalent to rdf:about="#name". rdf:ID provides an additional check since the same name can only appear once in the scope of an xml:base value (or document, if none is given), so is useful for defining a set of distinct, related terms relative to the same IRI.

Both forms require a base IRI to be determined, either from an in-scope xml:base or from the URL of the RDF/XML document.

shows abbreviating the node IRI of http://example.org/here/#snack using an xml:base of http://example.org/here/ and an rdf:ID on the rdf:Description node element. The object node of the ex:prop predicate is an IRI resolved from the rdf:resource XML attribute value using the in-scope base IRI to give the IRI http://example.org/here/fruit/apple.

RDF has a set of container membership properties and corresponding property elements that are mostly used with instances of the rdf:Seq, rdf:Bag, and rdf:Alt classes which may be written as typed node elements. The list properties are rdf:_1, rdf:_2 etc. and can be written as property elements or property attributes as shown in . There is an rdf:li special property element that is equivalent to rdf:_1, rdf:_2 in order, explained in detail in . The mapping to the container membership properties is always done in the order that the rdf:li special property elements appear in XML — the document order is significant. The equivalent RDF/XML to written in this form is shown in .

RDF/XML allows an rdf:parseType="Collection" attribute on a property element to let it contain multiple node elements. These contained node elements give the set of subject nodes of the collection. This syntax form corresponds to a set of triples connecting the collection of subject nodes, the exact triples generated are described in detail in . The collection construction is always done in the order that the node elements appear in the XML document. Whether the order of the collection of nodes is significant is an application issue and not defined here.

shows a collection of three nodes elements at the end of the ex:hasFruit property element using this form.

The rdf:ID attribute can be used on a property element to reify the triple that it generates (See for the full details). The identifier for the triple should be constructed as an IRI made from the relative IRI reference # concatenated with the rdf:ID attribute value, resolved against the in-scope base IRI. So for example if rdf:ID="triple", that would be equivalent to the IRI formed from relative IRI reference #triple against the base IRI. Each (rdf:ID attribute value, base IRI) pair has to be unique in an RDF/XML document, see constraint-id.

shows a rdf:ID being used to reify a triple made from the ex:prop property element giving the reified triple the IRI http://example.org/triples/#triple1.

A triple term may be the object of an RDF triple. triple terms in RDF graphs can be written in a form that allows a triple term to be written as a resource encoding a single RDF triple. This is done by adding the `rdf:parseType="Triple"` attribute on a property element to describe a single triple term, which may not appear as a triple within the graph, itself; see .

Triple terms play a similar role to Reifying Statements, the difference being that triple terms are are a core part of the RDF 1.2 Abstract Syntax [[RDF12-CONCEPTS]], while Reifying Statements emit triples to describe another triple in the asserted graph. Triple terms describe triples that are not necessarily asserted. See for a way to combine asserting and describing a triple at the same time.

RDF 1.2 XML Syntax also includes syntax for annotating triples by both asserting the triple, via an explicit identifier, and having the reifier associated with that triple terms be the subject or object of further triples. If explicitly identified, the same reifier can then be used as the subject or object of additional triples and/or triple terms.

A reifier can be added as a property attribute using either the `rdf:annotation` (for IRI reifier) or `rdf:annotationNodeID` (for blank node reifier). This reifier can also be used as the subject of other triples as a way to associate those triples with the triple term composed of the subject, predicate, and object associated with a property element.

All use of string without further qualification refers to a Unicode [[UNICODE]] character string; a sequence of characters represented by a code point in Unicode.

Definition:

An RDF/XML Document is an RDF Document written in the XML syntax for RDF as defined in this document.

Conformance:

An RDF/XML Document is a conforming RDF/XML document if it adheres to the specification defined in this document.

Contact:

Dan Brickley

See also:

How to Register a Media Type for a W3C Specification

Internet Media Type registration, consistency of use
TAG Finding 3 June 2002 (Revised 4 September 2002)

The Internet Media Type (formerly known as MIME Type) for RDF/XML is application/rdf+xml — [[RFC3870]].

It is recommended that RDF/XML files have the extension ".rdf" (all lowercase) on all platforms.

It is recommended that RDF/XML files stored on Macintosh HFS file systems be given a file type of "rdf " (all lowercase, with a space character as the fourth letter).

Features introduced in RDF 1.2 require a version announcement on an in-scope node element with an `rdf:version` attribute with a defined value other than `"1.1"`. Acceptable values for `rdf:version` are defined in 2.1 Version Lables in [[RDF12-CONCEPTS]]. Parser behavior for version values is otherwise undefined and MAY be used to signal errors or warnings.

The `application/rdf+xml` media type has been registered at IANA as [[RFC3870]].

The RDF/XML format is used to express arbitrary application data, which may include the expression of personally identifiable information (PII) or other information which could be considered sensitive. Authors publishing such information are advised to carefully consider the needs and use of publishing such information, as well as the applicable regulations for the regions where the data is expected to be consumed and potentially revealed (e.g., GDPR, CCPA, others), particularly whether authorization measures are needed for access to the data.

See the Security Considerations Section of [[RFC3870]].

The RDF namespace IRI (or namespace name) is http://www.w3.org/1999/02/22-rdf-syntax-ns# and is typically used in XML with the prefix rdf although other prefix strings may be used. The RDF Vocabulary is identified by this namespace name and consists of the following names only:

Syntax names — not concepts

RDF Description ID about annotation annotationNodeID datatype li nodeID parseType resource version

Class names

Seq Bag Alt Statement Property XMLLiteral List

Property names

subject predicate object type value first rest _n
where n is a decimal integer greater than zero with no leading zeros.

Resource names

nil

Any other names are not defined and SHOULD generate a warning when encountered, but should otherwise behave normally.

Within RDF/XML documents it is not permitted to use XML namespaces whose namespace name is the RDF namespace IRI concatenated with additional characters.

Throughout this document the terminology rdf:name will be used to indicate name is from the RDF Vocabulary and it has a IRI of the concatenation of the RDF namespace IRI and name. For example, rdf:type has the IRI http://www.w3.org/1999/02/22-rdf-syntax-ns#type

The RDF Concepts document [[RDF12-CONCEPTS]] defines the four types of RDF data that can act as node and/or predicate:

IRI

IRIs can act as node (both subject and object) and as predicate.

IRIs can be either:

• given as XML attribute values interpreted as relative IRI references that are resolved against the in-scope base IRI as described in to give resolved IRIs
• transformed from XML namespace-qualified element and attribute names (QNames)
• transformed from rdf:ID attribute values.

Within RDF/XML, XML QNames are transformed into IRIs by appending the XML local name to the namespace name (IRI). For example, if the XML namespace prefix foo has namespace name (IRI) http://example.org/somewhere/ then the QName foo:bar would correspond to the IRI http://example.org/somewhere/bar. Note that this restricts which IRIs can be made and the same IRI can be given in multiple ways.

The rdf:ID values are transformed into IRIs by appending the attribute value to the result of appending "#" to the in-scope base IRI which is defined in

Literal

Literals can only act as object nodes.

Literals always have a datatype. Language-tagged strings get the datatype rdf:langString. When there is no language tag or datatype specified, the literal is treated as if the datatype xsd:string was specified.

Blank Node

Blank nodes can act as subject node and as object node.

Blank nodes have distinct identity in the RDF graph. When the graph is written in a syntax such as RDF/XML, these blank nodes may need document-local identifiers and a syntax in order to preserve this distinction. These local identifiers are called blank node identifiers and are used in RDF/XML as values of the rdf:nodeID attribute with the syntax given in Production nodeIdAttr. Blank node identifiers in RDF/XML are scoped to the XML Information Set [[XML-INFOSET]] document information item.

If no blank node identifier is given explicitly as an rdf:nodeID attribute value then one will need to be generated (using generated-blank-node-id, see ). Such generated blank node identifiers MUST not clash with any blank node identifiers derived from rdf:nodeID attribute values. This can be implemented by any method that preserves the distinct identity of all the blank nodes in the graph, that is, the same blank node identifier is not given for different blank nodes. One possible method would be to add a constant prefix to all the rdf:nodeID attribute values and ensure no generated blank node identifiers ever used that prefix. Another would be to map all rdf:nodeID attribute values to new generated blank node identifiers and perform that mapping on all such values in the RDF/XML document.

Triple Term

Triple terms can only act as object nodes.

A triple term describes a triple, which may, or may not, be asserted in the graph.

RDF/XML supports XML Base [[XMLBASE]] which defines a ·base-iri· accessor for each ·root event· and ·element event·. Relative IRI references are resolved into IRIs according to the algorithm specified in [[XMLBASE]] and as per [[[RFC3986]]] [[RFC3986]] using only the basic algorithm in section 5.2. These specifications do not specify an algorithm for resolving a fragment identifier alone, such as #foo, or the empty string "" into an IRI. In RDF/XML, a fragment identifier is transformed into an IRI by appending the fragment identifier to the in-scope base IRI. The empty string is transformed into an IRI by substituting the in-scope base IRI.

An empty same document reference "" resolves against the URI part of the base IRI; any fragment part is ignored. See Uniform Resource Identifiers (URI) [[RFC3986]].

Implementation Note (Informative): When using a hierarchical base URI that has no path component (/), it must be added before using as a base IRI for resolving.

constraint-id

Each application of production idAttr matches an attribute. The ·rdf-term· accessor of the matched attribute is unique within a single RDF/XML document.

The syntax of the names MUST match the rdf-id production.

This document specifies the syntax of RDF/XML as a grammar on an alphabet of symbols. The symbols are called events in the style of the XPATH   Information Set Mapping. A sequence of events is normally derived from an XML document, in which case they are in document order as defined below in . The sequence these events form are intended to be similar to the sequence of events produced by the [[SAX]] XML API from the same XML document. Sequences of events may be checked against the grammar to determine whether they are or are not syntactically well-formed RDF/XML.

The RDF 1.2 Concepts and Abstract Syntax specification [[!RDF12-CONCEPTS]] defines four types of RDF terms: IRIs, literals, blank nodes, and triple terms. Literals are composed of a lexical form and an optional language tag [[!BCP47]] – possibly including a base direction – or datatype IRI. An extra type, prefix, is used during parsing to map string identifiers to namespace IRIs.

The grammar productions may include actions which fire when the production is recognized. Taken together these actions define a transformation from any syntactically well-formed RDF/XML sequence of events into a set of triples by mapping matching productions to RDF terms or their components (e.g., language tags, lexical forms of literals). Grammar productions change the parser state and emit triples.

The model given here illustrates one way to create a representation of an RDF Graph from an RDF/XML document. It does not mandate any implementation method — any other method that results in a representation of the same RDF Graph may be used.

In particular:

• This specification permits any representation of an RDF graph; in particular, it does not require the use of N-Triples [[RDF12-N-TRIPLES]].
• This specification does not require the use of [[XPATH]] or [[SAX]]
• This specification places no constraints on the order in which software transforming RDF/XML into a representation of a graph, constructs the representation of the graph.
• Software transforming RDF/XML into a representation of a graph MAY eliminate duplicate predicate arcs.

The syntax does not support non-well-formed XML documents, nor documents that otherwise do not have an XML Information Set [[XML-INFOSET]]; for example, that do not conform to Namespaces in XML [[XML-NAMES]].

The Infoset requires support for XML Base [[XMLBASE]]. RDF/XML uses the information item property [base IRI], discussed in

This specification requires an XML Information Set [[XML-INFOSET]] which supports at least the following information items and properties for RDF/XML:

document information item

[document element], [children], [base IRI]

element information item

[local name], [namespace name], [children], [attributes], [parent], [base IRI]

attribute information item

[local name], [namespace name], [normalized value]

character information item

[character code]

There is no mapping of the following items to data model events:

• processing instruction information item
• unexpanded entity reference information item
• comment information item
• document type declaration information item
• unparsed entity information item
• notation information item
• namespace information item

Other information items and properties have no mapping to syntax data model events.

Element information items with reserved XML Names (see Name in [[[XML11]]]) are not mapped to data model element events. These are all those with property [prefix] beginning with xml (case independent comparison) and all those with [prefix] property having no value and which have [local name] beginning with xml (case independent comparison).

All information items contained inside XML elements matching the parseTypeLiteralPropertyElt production form XML literals and do not follow this mapping. See parseTypeLiteralPropertyElt for further information.

This section is intended to satisfy the requirements for Conformance in the [[XML-INFOSET]] specification. It specifies the information items and properties that are needed to implement this specification.

There are nine types of event defined in the following subsections. Most events are constructed from an Infoset information item (except for IRI, blank node, literal with no explicit datatype and typed literal). The effect of an event constructor is to create a new event with a unique identity, distinct from all other events. Events have accessor operations on them and most have the string-value, IRI, rdf-term, literal, or bnode accessors that may be a static value or computed.

Constructed from a document information item and takes the following accessors and values.

document-element

Set to the value of document information item property [document-element].

children

Set to the value of document information item property [children].

base-iri

Set to the value of document information item property [base IRI].

language

Set to the empty string.

direction

Set to the empty string.

graph

The graph used for collecting emitted triples, initialized to a new RDF graph.

Constructed from an element information item and takes the following accessors and values:

local-name

Set to the value of element information item property [local name].

namespace-name

Set to the value of element information item property [namespace name].

children

Set to the value of element information item property [children].

parent

Set to the value of element information item property [parent].

base-iri

Set to the value of element information item property [base IRI].

attributes

Made from the value of element information item property [attributes] which is a set of attribute information items.

If this set contains an attribute information item xml:lang ([namespace name] property with the value `"http://www.w3.org/XML/1998/namespace"` and [local name] property value "lang") it is removed from the set of attribute information items and the ·language· accessor is set to the [normalized-value] property of the attribute information item.

If the element has a version accessor with the value `"1.2-basic"`, `"1.2"` or greater, this set contains an attribute information item its:dir ([namespace name] property with the value `"http://www.w3.org/2005/11/its"` and [local name] property value "dir") it is removed from the set of attribute information items and the ·direction· accessor is set to the [normalized-value] property of the attribute information item, which MUST be one of `"ltr"`, `"rtl"`, or the empty string.

If the element has a version accessor with the value `"1.2-basic"`, `"1.2"` or greater, this set contains an attribute information item its:version ([namespace name] property with the value `"http://www.w3.org/2005/11/its"` and [local name] property value "version") it is removed from the set of attribute information items and the ·its-version· accessor is set to the [normalized-value] property of the attribute information item.

All remaining reserved XML Names (see Name in [[[XML11]]]) are now removed from the set. These are, all attribute information items in the set with property [prefix] beginning with xml (case independent comparison) and all attribute information items with [prefix] property having no value and which have [local name] beginning with xml (case independent comparison) are removed. Note that the [base IRI] accessor is computed by XML Base before any xml:base attribute information item is deleted.

The remaining set of attribute information items are then used to construct a new set of Attribute Events which is assigned as the value of this accessor.

IRI

Set to an IRI constructed from the concatenation of the value of the namespace-name accessor and the value of the local-name accessor.

li-counter

Set to the integer value 1.

language

Set from the ·attributes· as described above. If no value is given from the attributes, the value is set to the value of the language accessor on the parent event (either a Root Event or an Element Event), which may be the empty string.

direction

Set from the ·attributes· as described above. If no value is given from the attributes, the value is set to the value of the direction accessor on the parent event (either a Root Event or an Element Event), which may be the empty string.

version

Set from the ·attributes· as described above. If no value is given from the attributes, the value is set to the value of the version accessor on the parent event (either a Root Event or an Element Event).

its-version

Set from the ·attributes· as described above. If no value is given from the attributes, the value is set to the value of the version accessor on the parent event (either a Root Event or an Element Event), which SHOULD be set to `"2.0"`.

subject

Has no initial value. Takes a value that is an Identifier event, or a triple term. This accessor is used on elements that deal with one node in the RDF graph, this generally being the subject of an RDF triple.

graph

The graph used for collecting emitted triples. The initial value is taken from the parent event (either a Root Event or an Element Event), or a new RDF graph, if not set. May be modified by a `parseType="Triple"` attribute.

Has no accessors. Marks the end of the containing element in the sequence.

Constructed from an attribute information item and takes the following accessors and values:

local-name

Set to the value of attribute information item property [local name].

namespace-name

Set to the value of attribute information item property [namespace name].

string-value

Set to the value of the attribute information item property [normalized value] as specified by [[XML11]] (if an attribute whose normalized value is a zero-length string, then the string-value is also a zero-length string).

IRI

If ·namespace-name· is present, set to an IRI constructed from the concatenation of the value of the ·namespace-name· accessor and the value of the ·local-name· accessor. Otherwise if ·local-name· is ID, about, parseType, resource, type, or version, set to an IRI constructed from the value of the concatenation of the RDF namespace IRI and the value of the local-name accessor. Other non-namespaced ·local-name· accessor values are forbidden.

The support for a limited set of non-namespaced names is REQUIRED and intended to allow RDF/XML documents specified in [[RDF-SYNTAX-GRAMMAR-19990222]] to remain valid; new documents SHOULD NOT use these unqualified attributes and applications MAY choose to warn when the unqualified form is seen in a document.

The construction of IRIs from XML attributes can generate the same IRIs from different XML attributes. This can cause ambiguity in the grammar when matching attribute events (such as when rdf:about and about XML attributes are both present). Documents that have this are illegal.

rdf-term

The value is an IRI constructed from string-value resolved against the ·base-iri· accessor of the containing element.

Constructed from a sequence of one or more consecutive character information items. Has the single accessor:

string-value

Set to the value of the string made from concatenating the [character code] property of each of the character information items.

An event for an IRI which has the following accessors:

identifier

Takes a string value used as an IRI.

rdf-term

The value is an IRI constructed from the value of the ·identifier· accessor.

These events are constructed by giving a value for the ·identifier· accessor.

For further information on identifiers in RDF, see .

An event for an triple term which has the following accessors:

rdf-term

The value is a triple term.

These events are constructed by giving a value to the rdf-term accessor.

An event for a blank node identifier which has the following accessors:

identifier

Takes a string value.

blank-node

The value is a blank node with local identifier taken from the ·identifier· accessor. Within an RDF/XML document, all blank nodes identified by the same identifier represent the same blank node.

These events are constructed by giving a value for the ·identifier· accessor.

For further information on identifiers in RDF, see .

RDF/XML literals without an explicit datatype in RDF 1.2 are treated as syntactic sugar for a literal with datatype xsd:string (when no language tag is present), as a literal with datatype rdf:langString (when a language tag is present and a direction is not present), or as a literal with datatype rdf:dirLangString (when both a language tag and a direction are present). The mapping to N-Triples as defined in this subsection is not affected by this change.

An event for a literal without an explicit datatype which can have the following accessors:

literal-value

Takes a string value.

literal-language

Takes a string value used as a language tag in language-tagged string.

literal-direction

Takes a string value used as a direction tag in a directional language-tagged strings.

literal

The value is an RDF literal constructed from the other accessors as follows.

If ·literal-language· is the empty string then the value is an RDF literal with the lexical form taken from the value of the ·literal-value· accessor and datatype IRI `xsd:string`.

Otherwise, if the ·literal-direction· is the empty string, then the value is a language-tagged string with the lexical form taken from the value of the ·literal-value· accessor and the language tag taken from the value of the ·literal-language· accessor.

Otherwise the value is a directional language-tagged string with the lexical form taken from the value of the ·literal-value· accessor, the language tag taken from the value of the ·literal-language· accessor, and the base direction taken from the value of the ·literal-direction· accessor.

These events are constructed by giving values for the ·literal-value·, ·literal-language·, and ·literal-direction· accessors.

Interoperability Note (Informative): Literals beginning with a Unicode combining character are allowed however they may cause interoperability problems. See [[?CHARMOD]] for further information.

An event for a typed literal which can have the following accessors:

literal-value

Takes a string value.

literal-datatype

Takes a string value used as an IRI.

literal

The value is an RDF literal with the lexical form taken from the value of the ·literal-value· accessor and datatype IRI taken from the value of the ·literal-datatype· accessor.

These events are constructed by giving values for the ·literal-value· and ·literal-datatype· accessors.

Interoperability Note (Informative): Literals beginning with a Unicode combining character are allowed however they may cause interoperability problems. See [[CHARMOD]] for further information.

Implementation Note (Informative): In XML Schema (part 1) [[XMLSCHEMA11-2]], white space normalization occurs during validation according to the value of the whiteSpace facet. The syntax mapping used in this document occurs after this, so the whiteSpace facet formally has no further effect.

To transform the Infoset into the sequence of events in document order, each information item is transformed as described above to generate a tree of events with accessors and values. Each element event is then replaced as described below to turn the tree of events into a sequence in document order.

1. The original element event
2. The value of the children accessor recursively transformed, a possibly empty ordered list of events.
3. An end element event

The following notation is used to describe matching the sequence of data model events as given in and the actions to perform for the matches. The RDF/XML grammar is defined in terms of mapping from these matched data model events to triples, using notation of the form:

number event-type event-content

where the event-content is an expression matching event-types (as defined in ), using notation given in the following sections. The number is used for reference purposes. The grammar action may include generating new triples to the graph.

The following sections describe the general notation used and that for event matching and actions.

If the RDF/XML is a standalone XML document (identified by presentation as an `application/rdf+xml` RDF media type object, or by some other means) then the grammar may start with production doc or production nodeElement.

If the content is known to be RDF/XML by context, such as when RDF/XML is embedded inside other XML content, then the grammar can either start at Element Event  RDF (only when an element is legal at that point in the XML) or at production nodeElementList (only when element content is legal, since this is a list of elements). For such embedded RDF/XML, the ·base-iri· value on the outermost element MUST be initialized from the containing XML since no Root Event  will be available. Note that if such embedding occurs, the grammar may be entered several times but no state is expected to be preserved.

Add tests for embedded RDF/XML.

The start node is referred to as the top-level XML document element.

rdf:RDF | rdf:ID | rdf:about | rdf:parseType | rdf:resource | rdf:nodeID | rdf:datatype | rdf:version

A subset of the syntax terms from the RDF Vocabulary in which are used in RDF/XML.

All the syntax terms from the RDF Vocabulary in which are used in RDF/XML.

rdf:aboutEach | rdf:aboutEachPrefix | rdf:bagID

These are the names from the RDF Vocabulary that have been withdrawn from the language. See the resolutions of Issue rdfms-aboutEach-on-object, Issue rdfms-abouteachprefix and Last Call Issue timbl-01 for further information.

The IRIs that are allowed on node elements.

The URIs that are allowed on property elements.

The IRIs that are allowed on property attributes.

For node element e, the processing of some of the attributes has to be done before other work such as dealing with children events or other attributes. These can be processed in any order:

• If there is an attribute a with a.IRI == rdf:ID, then e.subject := iri(identifier := resolve(e, concat("#", a.string-value))).
• If there is an attribute a with a.IRI == rdf:nodeID, then e.subject := bnodeid(identifier:=a.string-value).
• If there is an attribute a with a.IRI == rdf:about then e.subject := iri(identifier := e.rdf-term).

If e.subject is empty, then e.subject := bnodeid(identifier := generated-blank-node-id()).

The following can then be performed in any order:

• If e.IRI != rdf:Description then the following statement is added to e.parent.graph:
• If there is an attribute a in propertyAttr with a.IRI == rdf:type then u:=iri(identifier:=e.rdf-term) and the following triple is e.parent.graph:
• For each attribute a matching propertyAttr (and not rdf:type), the Unicode string a.string-value SHOULD be in Normal Form C [[NFC]], o := literal(literal-value := a.string-value, literal-language := e.language, literal-direction := e.direction) and the following statement is added to e.parent.graph:
• Handle the propertyEltList children events in document order.

If element e has e.IRI = rdf:li then apply the list expansion rules on element e.parent in to give a new IRI u and e.IRI := u.

The action of this production MUST be done before the actions of any sub-matches (resourcePropertyElt ... emptyPropertyElt). Alternatively the result MUST be equivalent to as if it this action was performed first, such as performing as the first action of all of the sub-matches.

For element e, and the single contained nodeElement n, first n MUST be processed using production nodeElement. Then the following statement is added to e.parent.graph:

If the rdf:ID attribute a is given, the above statement is reified with i := iri(identifier := resolve(e, concat("#", a.string-value))) using the reification rules in and e.subject := i

If either the rdf:annotation or rdf:annotationNodeID attributes a are given, the statement above is used to create a triple term t, and the following statement is added to e.parent.graph:

Note that the empty literal case is defined in production emptyPropertyElt.

For element e, and the text event t. The Unicode string t.string-value SHOULD be in Normal Form C [[NFC]]. If the rdf:datatype attribute d is given then o := typed-literal(literal-value := t.string-value, literal-datatype := d.rdf-term) otherwise o := literal(literal-value := t.string-value, literal-language := e.language, literal-direction := e.direction) and the following statement is added to e.parent.graph:

If the rdf:ID attribute a is given, the above statement is reified with i := iri(identifier := resolve(e, concat("#", a.string-value))) using the reification rules in and e.subject := i.

If either the rdf:annotation or rdf:annotationNodeID attributes a are given, the statement above is used to create a triple term t, and the following statement is added to e.parent.graph:

For element e and the literal l that is the rdf:parseType="Literal" content. l is not transformed by the syntax data model mapping into events (as noted in section ) but remains an XML Infoset of XML Information items.

l is transformed into the lexical form of an XML literal in the RDF graph x (a Unicode string) by the following algorithm. This does not mandate any implementation method — any other method that gives the same result may be used.

1. Use l to construct an XPath sequence [[XPATH-DATAMODEL-30]].
2. Apply https://www.w3.org/TR/xpath-functions-30/#func-serialize [[XPATH-FUNCTIONS-30]] to this sequence to give an xsd:string x.
3. The Unicode string x is used as the lexical form of l
4. This Unicode string x SHOULD be in NFC Normal Form C [[NFC]]

Then o := typed-literal(literal-value := x, literal-datatype := http://www.w3.org/1999/02/22-rdf-syntax-ns#XMLLiteral ) and the following statement is added to e.parent.graph:

If the rdf:ID attribute a is given, the above statement is reified with i := iri(identifier := resolve(e, concat("#", a.string-value))) using the reification rules in and e.subject := i.

If either the rdf:annotation or rdf:annotationNodeID attributes a are given, the statement above is used to create a triple term t, and the following statement is added to e.parent.graph:

For element e with possibly empty element content c.

n := bnodeid(identifier := generated-blank-node-id()).

Add the following statement to e.parent.graph:

If the rdf:ID attribute a is given, the statement above is reified with i := iri(identifier := resolve(e, concat("#", a.string-value))) using the reification rules in and e.subject := i.

If either the rdf:annotation or rdf:annotationNodeID attributes a are given, the statement above is used to create a triple term t, and the following statement is added to e.parent.graph:

If the element content c is not empty, then use event n to create a new sequence of events as follows:

Then process the resulting sequence using production nodeElement.

For element e with element content c.

Create a new sequence of events as follows:

Then process the resulting sequence using production nodeElement.

After processing the node sequence, e.parent.graph MUST be an RDF graph containing a single triple.

e.subject := triple(s, p, o), where s, p, and o are the subject, predicate, and object of the sole triple in e.parent.graph.

Add the following statement added to e.parent.graph:

For element event e with possibly empty nodeElementList l. Set s:=list().

For each element event f in l, n := bnodeid(identifier := generated-blank-node-id()) and append n to s to give a sequence of events.

If s is not empty, n is the first event identifier in s and the following statement is added to e.parent.graph:

otherwise the following statement is added to e.parent.graph:

If the rdf:ID attribute a is given, either of the the above statements is reified with i := iri(identifier := resolve(e, concat("#", a.string-value))) using the reification rules in .

If either the rdf:annotation or rdf:annotationNodeID attributes a are given, the statement above is used to create a triple term t, and the following statement is added to e.parent.graph:

If s is empty, no further work is performed.

For each event n in s and the corresponding element event f in l, the following statement is added to e.parent.graph:

For each consecutive and overlapping pair of events (n, o) in s, the following statement is added to e.parent.graph:

If s is not empty, n is the last event identifier in s, the following statement is added to e.parent.graph:

n.rdf-term <http://www.w3.org/1999/02/22-rdf-syntax-ns#rest> <http://www.w3.org/1999/02/22-rdf-syntax-ns#nil> .

All rdf:parseType attribute values other than the strings "Resource", "Literal", "Collection", or "Triple" are treated as if the value was "Literal". This production matches and acts as if production parseTypeLiteralPropertyElt was matched. No extra triples are generated for other rdf:parseType values.

• If there are no attributes or only the optional rdf:ID attribute i, or the optional attributes `rdf:annotation` or `rdf:annotationNodeID` a, then o := literal(literal-value:="", literal-language := e.language, literal-direction := e.direction) and the following statement is added to e.parent.graph:

  and then if i is given, the above statement is reified with iri(identifier := resolve(e, concat("#", i.string-value))) using the reification rules in .

  and then if a is given, the statement above is used to create a triple term t, and the following statement is added to e.parent.graph:

• Otherwise

  • If rdf:resource attribute i is present, then r := iri(identifier := i.rdf-term)
  • If rdf:nodeID attribute i is present, then r := bnodeid(identifier := i.string-value)
  • If neither, r := bnodeid(identifier := generated-blank-node-id())

  The following are done in any order:

  • For all propertyAttr attributes a (in any order)

    • If a.IRI == rdf:type then u:=iri(identifier:=i.rdf-term) and the following triple is added to e.parent.graph:

    • Otherwise Unicode string a.string-value SHOULD be in Normal Form C [[NFC]], o := literal(literal-value := a.string-value, literal-language := e.language, literal-direction := e.direction) and the following statement is added to e.parent.graph:

  • Add the following statement to the graph:

    and then if rdf:ID attribute i is given, the above statement is reified with iri(identifier := resolve(e, concat("#", i.rdf-term))) using the reification rules in .

    and then if either the rdf:annotation or rdf:annotationNodeID attributes a are given, the statement above is used to create a triple term t, and the following statement is added to e.parent.graph:

Constraint:: constraint-id applies to the values of rdf:ID attributes

This production MAY be ignored unless rdf:version is `"1.2"` or greater.

This production MAY be ignored unless rdf:version is `"1.2"` or greater.

For the given IRI event r and the statement with terms s, p and o corresponding to the N-Triples:

add the following statements to the graph:

r.rdf-term <http://www.w3.org/1999/02/22-rdf-syntax-ns#subject> s .
r.rdf-term <http://www.w3.org/1999/02/22-rdf-syntax-ns#predicate> p .
r.rdf-term <http://www.w3.org/1999/02/22-rdf-syntax-ns#object> o .
r.rdf-term <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://www.w3.org/1999/02/22-rdf-syntax-ns#Statement> .

For the given element e, create a new IRI u := concat("http://www.w3.org/1999/02/22-rdf-syntax-ns#_", e.li-counter), increment the e.li-counter property by 1 and return u.

There are some RDF graphs as defined in [[RDF12-CONCEPTS]] that cannot be serialized in RDF/XML. These are the graphs that:

Use property names that cannot be turned into XML namespace-qualified names.

An XML namespace-qualified name (QName) has restrictions on the legal characters such that not all property URIs can be expressed as these names. It is recommended that implementors of RDF serializers, in order to break a URI into a namespace name and a local name, split it after the last XML non-NCName character, ensuring that the first character of the name is a Letter or '_'. If the URI ends in a non-NCName character then throw a "this graph cannot be serialized in RDF/XML" exception or error.

Use inappropriate reserved names as properties

For example, a property with the same URI as any of the syntaxTerms production.

Implementation Note (Informative): When an RDF graph is serialized to RDF/XML and has an XML Schema Datatype (XSD), it SHOULD be written in a form that does not require whitespace processing. XSD support is NOT required by RDF or RDF/XML so this is optional.

There is a standardized approach for associating RDF compatible metadata with SVG — the metadata element which was explicitly designed for this purpose as defined in Section 21 Metadata of the [[[SVG10]]] [[SVG10]] and [[[SVG11]]] [[SVG11]].

This document contains two example graphs in SVG with such embedded RDF/XML inside the metadata element: figure 1 and figure 2.

This document is a product of extended deliberations by the RDF Core working group, whose members have included: Art Barstow (W3C) Dave Beckett (ILRT), Dan Brickley (W3C/ILRT), Dan Connolly (W3C), Jeremy Carroll (Hewlett Packard), Ron Daniel (Interwoven Inc), Bill dehOra (InterX), Jos De Roo (AGFA), Jan Grant (ILRT), Graham Klyne (Clearswift and 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), 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), RV 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.), Lauren Wood (SoftQuad).

Gavin Carothers provided the RDF 1.1 update for the Production parseTypeLiteralPropertyElt. Ivan Herman provided valuable comments and reworked Figs 1 and 2.

This specification is a product of extended deliberations by the members of the RDFcore Working Group and the RDF and RDF Schema Working Group.

The following people provided valuable contributions to the document:

• Dan Brickley, W3C/ILRT
• Jeremy Carroll, HP Labs, Bristol
• Graham Klyne, Nine by Nine
• Bijan Parsia, MIND Lab at University of Maryland at College Park

In addition to the editors, the following people have contributed to this specification:

Recognize members of the Task Force? Not an easy to find list of contributors.

• Adds and .
• Updates reference for [[SAX]].
• Removes the statement that the `rdf:HTML` datatype cannot be serialized in RDF/XML.
• Adds and rdf:version.
• The processing model now emits RDF terms and triples directly, rather than N-Triples [[RDF12-N-TRIPLES]]; this is more consistent with other concrete RDF syntaxes. The names of some event accessors have been updated accordingly.
• Adds , , and to support Triple Terms.
• Adds and rules for creating reifiers for Triple Terms, allowing them to be used as the subject or object of other triples.

This appendix contains XML schemas for validating RDF/XML forms. These are example schemas for information only and are not part of this specification.

This is an example schema in RELAX NG Compact (for ease of reading) for RDF/XML. Applications can also use the RELAX NG XML version. These formats are described in [[[RELAXNG-SCHEMA]]] [[RELAXNG-SCHEMA]].

The RNGC schema has been updated to attempt to match the grammar but this has not been checked or used to validate RDF/XML.

    #
    # RELAX NG Compact Schema for RDF/XML Syntax
    #
    # This schema is for information only and NON-NORMATIVE
    #
    # It is based on one originally written by James Clark in
    # https://lists.w3.org/Archives/Public/www-rdf-comments/2001JulSep/0248.html
    # and updated with later changes.
    #

    namespace local = ""
    namespace rdf = "http://www.w3.org/1999/02/22-rdf-syntax-ns#"
    datatypes xsd = "http://www.w3.org/2001/XMLSchema-datatypes"
    namespace its = "http://www.w3.org/2005/11/its"

    start = doc

    # I cannot seem to do this in RNGC so they are expanded in-line

    # coreSyntaxTerms = rdf:RDF | rdf:ID | rdf:annotation | rdf:annotationNodeID | rdf:about | rdf:parseType | rdf:resource | rdf:nodeID | rdf:datatype | rdf:version
    # syntaxTerms = coreSyntaxTerms | rdf:Description | rdf:li
    # oldTerms    = rdf:aboutEach | rdf:aboutEachPrefix | rdf:bagID
    # nodeElementIRIs       = * - ( coreSyntaxTerms | rdf:li | oldTerms )
    # propertyElementURIs   = * - ( coreSyntaxTerms | rdf:Description | oldTerms )
    # propertyAttributeIRIs = * - ( coreSyntaxTerms | rdf:Description | rdf:li | oldTerms )

    # Also needed to allow rdf:li on all property element productions
    # since we can't capture the rdf:li rewriting to rdf_<n> in relaxng

    # Need to add these explicitly
    xmllang = attribute xml:lang { text }
    xmlbase = attribute xml:base { text }
    # and to forbid every other xml:* attribute, element

    doc =
      RDF | nodeElement

    RDF =
      element rdf:RDF {
         xmllang?, xmlbase?, nodeElementList
    }

    nodeElementList =
      nodeElement*

      # Should be something like:
      #  ws* , (  nodeElement , ws* )*
      # but RELAXNG does this by default, ignoring whitespace separating tags.

    nodeElement =
      element * - ( local:* | rdf:RDF | rdf:ID | rdf:about | rdf:parseType |
                    rdf:resource | rdf:nodeID | rdf:datatype | rdf:li |
                    rdf:aboutEach | rdf:aboutEachPrefix | rdf:bagID ) {
          (idAttr | nodeIdAttr | aboutAttr )?, xmllang?, xmlbase?, propertyAttr*, propertyEltList
      }

      # It is not possible to say "and not things
      # beginning with _ in the rdf: namespace" in RELAX NG.

    ws =
      " "

      # Not used in this RELAX NG schema; but should be any legal XML
      # whitespace defined by https://www.w3.org/TR/2000/REC-xml-20001006#NT-S


    propertyEltList =
      propertyElt*

      # Should be something like:
      #  ws* , ( propertyElt , ws* )*
      # but RELAXNG does this by default, ignoring whitespace separating tags.

    propertyElt =
      resourcePropertyElt |
      literalPropertyElt |
      parseTypeLiteralPropertyElt |
      parseTypeResourcePropertyElt |
      parseTypeTriplePropertyElt |
      parseTypeCollectionPropertyElt |
      parseTypeOtherPropertyElt |
      emptyPropertyElt

    resourcePropertyElt =
      element * - ( local:* | rdf:RDF | rdf:ID |
                    rdf:annotation | rdf:annotationNodeID |
                    rdf:about | rdf:parseType |
                    rdf:resource | rdf:nodeID | rdf:datatype | rdf:version |
                    its:dir | its:version |
                    rdf:Description | rdf:aboutEach | rdf:aboutEachPrefix | rdf:bagID |
                    xml:* ) {
          idAttr?, (annotationAttr | annotationNodeIDAttr)?, xmllang?, xmlbase?, versionAttr?, dirAttr?, itsVersionAttr?, nodeElement
      }

    literalPropertyElt =
      element * - ( local:* | rdf:RDF | rdf:ID |
                    rdf:annotation | rdf:annotationNodeID |
                    rdf:about | rdf:parseType |
                    rdf:resource | rdf:nodeID | rdf:datatype | rdf:version |
                    its:dir | its:version |
                    rdf:Description | rdf:aboutEach | rdf:aboutEachPrefix | rdf:bagID |
                    xml:* ) {
          idAttr? , (annotationAttr | annotationNodeIDAttr)?, datatypeAttr?, xmllang?, xmlbase?, versionAttr?, dirAttr?, itsVersionAttr?, text
      }

    parseTypeLiteralPropertyElt =
      element * - ( local:* | rdf:RDF | rdf:ID |
                    rdf:annotation | rdf:annotationNodeID |
                    rdf:about | rdf:parseType |
                    rdf:resource | rdf:nodeID | rdf:datatype | rdf:version |
                    its:dir | its:version |
                    rdf:Description | rdf:aboutEach | rdf:aboutEachPrefix | rdf:bagID |
                    xml:* ) {
          idAttr?, (annotationAttr | annotationNodeIDAttr)?, parseLiteral, xmllang?, xmlbase?, versionAttr?, dirAttr?, itsVersionAttr?, literal
      }

    parseTypeResourcePropertyElt =
      element * - ( local:* | rdf:RDF | rdf:ID |
                    rdf:annotation | rdf:annotationNodeID |
                    rdf:about | rdf:parseType |
                    rdf:resource | rdf:nodeID | rdf:datatype | rdf:version |
                    its:dir | its:version |
                    rdf:Description | rdf:aboutEach | rdf:aboutEachPrefix | rdf:bagID |
                    xml:* ) {
          idAttr?, (annotationAttr | annotationNodeIDAttr)?, parseResource, xmllang?, xmlbase?, versionAttr?, dirAttr?, itsVersionAttr?, propertyEltList
      }

    parseTypeTriplePropertyElt =
      element * - ( local:* | rdf:RDF | rdf:about | rdf:parseType |
                    rdf:resource | rdf:nodeID | rdf:datatype | rdf:version |
                    its:dir | its:version |
                    rdf:Description | rdf:aboutEach | rdf:aboutEachPrefix | rdf:bagID |
                    xml:* ) {
          idAttr?, (annotationAttr | annotationNodeIDAttr)?, parseResource, xmllang?, xmlbase?, versionAttr?, dirAttr?, itsVersionAttr?, propertyEltList
      }

    parseTypeCollectionPropertyElt =
      element * - ( local:* | rdf:RDF | rdf:ID |
                    rdf:annotation | rdf:annotationNodeID |
                    rdf:about | rdf:parseType |
                    rdf:resource | rdf:nodeID | rdf:datatype | rdf:version |
                    its:dir | its:version |
                    rdf:Description | rdf:aboutEach | rdf:aboutEachPrefix | rdf:bagID |
                    xml:* ) {
          idAttr?, (annotationAttr | annotationNodeIDAttr)?, xmllang?, xmlbase?, versionAttr?, dirAttr?, itsVersionAttr?, parseCollection, nodeElementList
      }

    parseTypeOtherPropertyElt =
      element * - ( local:* | rdf:RDF | rdf:ID |
                    rdf:annotation | rdf:annotationNodeID |
                    rdf:about | rdf:parseType |
                    rdf:resource | rdf:nodeID | rdf:datatype | rdf:version |
                    its:dir | its:version |
                    rdf:Description | rdf:aboutEach | rdf:aboutEachPrefix | rdf:bagID |
                    xml:* ) {
          idAttr?, (annotationAttr | annotationNodeIDAttr)?, xmllang?, xmlbase?, versionAttr?, dirAttr?, itsVersionAttr?, parseOther, any
      }

    emptyPropertyElt =
       element * - ( local:* | rdf:RDF | rdf:ID |
                     rdf:annotation | rdf:annotationNodeID |
                     rdf:about | rdf:parseType |
                     rdf:resource | rdf:nodeID | rdf:datatype | rdf:version |
                     its:dir | its:version |
                     rdf:Description | rdf:aboutEach | rdf:aboutEachPrefix | rdf:bagID |
                     xml:* ) {
           idAttr?, (resourceAttr | nodeIdAttr | datatypeAttr )?, xmllang?,
           xmlbase?, versionAttr?, dirAttr?, itsVersionAttr?, propertyAttr*
       }

    idAttr =
      attribute rdf:ID {
          IDsymbol
      }

    nodeIdAttr =
      attribute rdf:nodeID {
          IDsymbol
      }

    aboutAttr =
      attribute rdf:about {
          IRI
      }

    propertyAttr =
      attribute * - ( local:* | rdf:RDF | rdf:ID |
                      rdf:annotation | rdf:annotationNodeID |
                      rdf:about | rdf:parseType |
                      rdf:resource | rdf:nodeID | rdf:datatype | rdf:version |
                      rdf:li | its:dir | | its:version
                      rdf:Description | rdf:aboutEach |
                      rdf:aboutEachPrefix | rdf:bagID |
                      xml:* ) {
          string
      }

    resourceAttr =
      attribute rdf:resource {
          IRI
      }

    datatypeAttr =
      attribute rdf:datatype {
          IRI
      }

    parseLiteral =
      attribute rdf:parseType {
          "Literal"
      }

    parseResource =
      attribute rdf:parseType {
          "Resource"
      }

    parseTriple =
      attribute rdf:parseType {
          "Triple"
      }

    parseCollection =
      attribute rdf:parseType {
          "Collection"
      }

    parseOther =
      attribute rdf:parseType {
          text
      }

    versionAttr =
      attribute rdf:version {
          text
      }

    dirAttr =
      attribute its:dir {
          text
      }

    itsVersionAttr =
      attribute its:version {
          text
      }

    IRI =
      string

    literal =
      any

    IDsymbol =
      xsd:NMTOKEN

    any =
      mixed { element * { attribute * { text }*, any }* }
    

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