RDF Serialization Formats

RDF is an abstract model, NOT a file format.

Multiple serializations exist to represent this abstract model in a textual format. Different ways of writing down the same graph lead to exactly the same triples and are thus logically equivalent.

The use cases for each:

• The Turtle family covers all the basic concepts for serializing RDF:

  • N-Triples: Streaming, bulk processing, and line-oriented tools (e.g. grep, wc).

  • N-Quads: Same as N-Triples, but when you need named graphs.

  • Turtle: Reading, writing, and editing RDF by hand.

  • TriG: Same as Turtle, but when you need named graphs.

• JSON-LD: Web APIs and schema.org markup.

• RDFa: Embedding RDF directly in HTML pages for search engines.

• RDF/XML: Legacy systems that expect XML.

Turtle Family ​

N-Triples ​

N-Triples is the simplest format. The rules are:

• Each line represents exactly one triple, terminated by a period.

• Every IRI must be written in full inside <>, with no prefixes or shortcuts allowed.

• Each line is fully self-contained, so no parser state is needed between lines.

This design enables line-oriented processing: files can be grep-ed for an IRI, wc -l-ed to count triples, or cat-ed together and the result remains valid N-Triples.

<http://example.org/bob#me> <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://xmlns.com/foaf/0.1/Person> .
<http://example.org/bob#me> <http://xmlns.com/foaf/0.1/knows> <http://example.org/alice#me> .
<http://example.org/bob#me> <http://schema.org/birthDate> "1990-07-04"^^<http://www.w3.org/2001/XMLSchema#date> .
<http://www.wikidata.org/entity/Q12418> <http://purl.org/dc/terms/title> "Mona Lisa" .
<http://www.wikidata.org/entity/Q12418> <http://purl.org/dc/terms/title> "La Joconde"@fr .

Literals are written as follows:

• Datatypes are appended via ^^, e.g. "1990-07-04"^^<...xsd#date>.

• String literals (xsd:string) may omit the datatype: "Mona Lisa" is equivalent to "Mona Lisa"^^xsd:string.

• Language-tagged strings use @lang after the closing quote, e.g. "La Joconde"@fr. Their implicit datatype is rdf:langString and is never written explicitly.

N-Quads ​

N-Quads extends N-Triples with support for RDF datasets. An optional fourth element on each line holds the graph IRI. Lines without a fourth element belong to the default graph and are otherwise identical to N-Triples.

<http://example.org/bob#me> <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://xmlns.com/foaf/0.1/Person> <http://example.org/bob> .
<http://www.wikidata.org/entity/Q12418> <http://purl.org/dc/terms/title> "Mona Lisa" <https://www.wikidata.org/wiki/Special:EntityData/Q12418> .
<http://example.org/bob> <http://purl.org/dc/terms/publisher> <http://example.org> .

Like N-Triples, N-Quads is used for exchanging large RDF datasets with line-oriented tools.

Turtle ​

Turtle is a superset of N-Triples: every valid N-Triples document is valid Turtle. It adds readability shortcuts on top:

• PREFIX/BASE: declare namespace prefixes so short forms like foaf:knows expand to full IRIs.

• ;: repeat the same subject with a new predicate-object pair.

• ,: repeat the same subject and predicate with a new object.

• a: shorthand for rdf:type.

• #: line comment.

• _:label: a blank node with a local reusable label.

• [ ... ]: an anonymous blank node inline (syntactic sugar for a fresh _: label plus extra triples).

PREFIX foaf: <http://xmlns.com/foaf/0.1/>
PREFIX schema: <http://schema.org/>
PREFIX xsd: <http://www.w3.org/2001/XMLSchema#>
PREFIX dcterms: <http://purl.org/dc/terms/>
PREFIX wd: <http://www.wikidata.org/entity/>

<http://example.org/bob#me>
    a foaf:Person ;                          # rdf:type shorthand
    foaf:knows <http://example.org/alice#me> ;
    schema:birthDate "1990-07-04"^^xsd:date ;
    foaf:topic_interest wd:Q12418 .

wd:Q12418
    dcterms:title "Mona Lisa", "La Joconde"@fr ;   # comma: same subject+predicate
    dcterms:creator <http://dbpedia.org/resource/Leonardo_da_Vinci> .

Language and direction (RDF 1.2), see RDF Data Model: Literals:

• "value"@lang: a language-tagged string.

• "value"@lang--rtl (or --ltr): a directional language-tagged string.

wd:Q12418
    dcterms:title "Mona Lisa"@en ;
    dcterms:title "La Joconde"@fr ;
    dcterms:title "موناليزا"@ar--rtl .

Turtle 1.2 provides three syntaxes for reifying triples, see RDF Data Model: Triple Terms:

• {| P O ; ... |}: an unnamed inline annotation attached directly to the preceding triple.

• << S P O >> in subject position: an unnamed reifier referencing a triple term.

• ~ <iri> or ~ _:label after a triple: a named reifier that can be referenced elsewhere.

# Unnamed inline annotation
<bob#me> foaf:topic_interest wd:Q12418
    {| dcterms:date "1998-10-04"^^xsd:date |} .

# Named reifier
<bob#me> foaf:topic_interest wd:Q12418
    ~ <http://example.org/bob#interest-1> .

<http://example.org/bob#interest-1>
    a prov:Influence ;
    dcterms:date "1998-10-04"^^xsd:date .

TriG ​

TriG extends Turtle with support for RDF datasets. Triples are wrapped in GRAPH <iri> { ... } to assign them to a named graph. The GRAPH keyword is optional. Triples outside any block form the default graph. In RDF 1.2, every Turtle document is also valid TriG (the names are kept for historical reasons).

PREFIX foaf: <http://xmlns.com/foaf/0.1/>
PREFIX dcterms: <http://purl.org/dc/terms/>
PREFIX wd: <http://www.wikidata.org/entity/>

GRAPH <http://example.org/bob> {
    <http://example.org/bob#me>
        a foaf:Person ;
        foaf:topic_interest wd:Q12418 .
}

GRAPH <https://www.wikidata.org/wiki/Special:EntityData/Q12418> {
    wd:Q12418
        dcterms:title "Mona Lisa" ;
        dcterms:creator <http://dbpedia.org/resource/Leonardo_da_Vinci> .
}

# Default graph
<http://example.org/bob>
    dcterms:publisher <http://example.org> ;
    dcterms:rights <http://creativecommons.org/licenses/by/3.0/> .

JSON-LD ​

JSON-LD provides a JSON syntax for RDF graphs and datasets. It is designed for minimal friction when converting existing JSON to RDF and for use in Web APIs and schema.org markup.

A @context object maps friendly JSON keys to full IRIs and specifies datatypes, so the rest of the document reads like regular JSON. The @context can be inlined or referenced as an external URL.

Each JSON object represents an RDF resource, with the following special keys:

• @id: the IRI of the resource.

• @type: maps to rdf:type.

• Nested objects express related resources.

• @graph: serializes a full RDF dataset.

{
  "@context": {
    "foaf": "http://xmlns.com/foaf/0.1/",
    "Person": "foaf:Person",
    "knows": { "@id": "foaf:knows", "@type": "@id" },
    "birthdate": {
      "@id": "http://schema.org/birthDate",
      "@type": "http://www.w3.org/2001/XMLSchema#date"
    },
    "dcterms": "http://purl.org/dc/terms/",
    "title": "dcterms:title",
    "creator": { "@id": "dcterms:creator", "@type": "@id" }
  },
  "@id": "http://example.org/bob#me",
  "@type": "Person",
  "birthdate": "1990-07-04",
  "knows": "http://example.org/alice#me",
  "interest": {
    "@id": "http://www.wikidata.org/entity/Q12418",
    "title": "Mona Lisa",
    "creator": "http://dbpedia.org/resource/Leonardo_da_Vinci"
  }
}

The context controls how values are interpreted:

• "@type": "@id": the value is treated as an IRI, not a plain string.

• "@type": "<datatype IRI>": a datatype is attached to the literal value.

• "@reverse": "<property IRI>": the triple direction is inverted, so "key": "x" becomes <x> <property> <current resource>.

RDFa ​

RDFa embeds RDF triples as attributes inside HTML (or XML) so search engines can extract structured data while crawling. The RDF lives directly in the page the browser already renders, with no separate file needed.

RDFa introduces the following HTML attributes:

• prefix: declares namespace shorthands, similar to Turtle PREFIX.

• resource: specifies the IRI of the subject (or object when used without property).

• typeof: asserts rdf:type for the enclosing element's resource.

• property: names the predicate IRI; the object is taken from href, resource, or element content.

• datatype: provides an explicit datatype for a literal; HTML semantics can supply it implicitly (e.g. the <time> element implies xsd:date).

<body
  prefix="foaf: http://xmlns.com/foaf/0.1/ schema: http://schema.org/ dcterms: http://purl.org/dc/terms/"
>
  <div resource="http://example.org/bob#me" typeof="foaf:Person">
    <p>
      Bob knows
      <a property="foaf:knows" href="http://example.org/alice#me">Alice</a> and
      was born on
      <time property="schema:birthDate" datatype="xsd:date">1990-07-04</time>.
    </p>
    <p>
      Bob is interested in
      <span
        property="foaf:topic_interest"
        resource="http://www.wikidata.org/entity/Q12418"
        >the Mona Lisa</span
      >.
    </p>
  </div>
  <div resource="http://www.wikidata.org/entity/Q12418">
    <p>
      The <span property="dcterms:title">Mona Lisa</span> was painted by
      <a
        property="dcterms:creator"
        href="http://dbpedia.org/resource/Leonardo_da_Vinci"
        >Leonardo da Vinci</a
      >.
    </p>
  </div>
</body>

RDF/XML ​

RDF/XML is the original RDF serialization from the late 1990s, written in XML. It is verbose and today mostly appears in legacy systems.

RDF/XML is structured as follows:

• All triples are nested inside an <rdf:RDF> root element that carries xmlns: namespace declarations.

• Each <rdf:Description rdf:about="..."> block groups triples that share a subject.

• Property subelements name the predicate: IRI objects use rdf:resource="...", literal objects are placed as element content.

• The rdf:datatype attribute attaches a datatype; omitting it defaults to xsd:string.

• Namespace prefixes apply only to XML element and attribute names, so full IRIs are required in rdf:about, rdf:resource, and rdf:datatype attribute values.

<?xml version="1.0" encoding="utf-8"?>
<rdf:RDF xmlns:dcterms="http://purl.org/dc/terms/"
         xmlns:foaf="http://xmlns.com/foaf/0.1/"
         xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
         xmlns:schema="http://schema.org/">
  <rdf:Description rdf:about="http://example.org/bob#me">
    <rdf:type rdf:resource="http://xmlns.com/foaf/0.1/Person"/>
    <schema:birthDate rdf:datatype="http://www.w3.org/2001/XMLSchema#date">1990-07-04</schema:birthDate>
    <foaf:knows rdf:resource="http://example.org/alice#me"/>
    <foaf:topic_interest rdf:resource="http://www.wikidata.org/entity/Q12418"/>
  </rdf:Description>
  <rdf:Description rdf:about="http://www.wikidata.org/entity/Q12418">
    <dcterms:title>Mona Lisa</dcterms:title>
    <dcterms:creator rdf:resource="http://dbpedia.org/resource/Leonardo_da_Vinci"/>
  </rdf:Description>
</rdf:RDF>