N3 Notation

Contents 1 RDF Triples and N3 2 Short Syntax for N3 (using semicolon) 3 Namespace declarations 4 N3 representation of a RDF graph 5 Rules in N3 6 N3 Rules Processors and Open Issues

RDF Triples and N3

<rdf:Description rdf:about="ex:adrian">
  <foaf:knows rdf:resource="ex:gerd"/>
  <foaf:age rdf:datatype="xs:int">41</ex:age>
</rdf:Description>

// N3 Syntax
ex:adrian foaf:knows ex:gerd.
ex:adrian foaf:age "41"^^xs:int.

Short Syntax for N3 (using semicolon)

ex:adrian foaf:knows ex:gerd; foaf:age "41"^^xs:int.

Namespace declarations

@prefix ex: <http://www.example.org/persons#> 

or

@prefix : <http://www.mydefaultnamespace.org/#> 

for the default namespace.

If nodes are from the default namespace we can write:

:adrian :child [ foaf:age "11"^^xs:int ] , [ foaf:age "3"^^xs:int ].

N3 representation of a RDF graph

// XML Syntax
<rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
    xmlns:m="http://www.example.org/meeting_organization#"
    xmlns:g="http://www.another.example.org/geographical#">
    <rdf:Description about="http://meetings.example.com/cal#m1">
        <m:Location parseType="Resource">
            <g:zip>02139</g:zip>
            <g:lat>14.124425</g:lat>
            <g:long>14.245</g:long>
        </m:Location>
        <m:chair rdf:resource="http://www.example.org/people#fred"/>
    </rdf:Description>
</rdf:RDF>

translates in N3 as:

// N3 notation
@prefix m:  <http://www.example.org/meeting_organization#> .
@prefix g:  <http://www.another.example.org/geographical#> .
<http://meetings.example.com/cal#m1>
  m:Location [ g:zip "02139"; g:lat "14.124425"; g:long "14.245" ];
  m:chair   <http://www.example.org/people#fred>.

Rules in N3

Variables are denoted like any other resource but identified by declarations:

// universally quantified variables
@forAll :x, :y.
{ :x :parent :y } =>  { :y ex:child :x }.

// existentially quantified variables
@forSome :a.
:Joe :home :a.
:a   :owner :Joe.
:a   :phone "555-1212".

You can use ? to denote universally quantifies variables and _ for the existentially quantified ones.

{ :?x :parent :?y } =>  { :?y ex:child :?x }.

:Joe :home :_a.
:_a   :owner :Joe.
:_a   :phone "555-1212".

N3 Rules Processors and Open Issues

• Rules are processed with CWM, a forward chaining reasoner which can be used for querying, checking, transforming and filtering information. Its core language is RDF, extended to include rules, and it uses RDF/XML or RDF/N3 serializations as required
• Open issues: negation, disjunction, existential quantified variables in rule consequent, datatypes usage.

See also: Semantic Web Tutorial Using N3 by Tim Berners-Lee, Sandro Hawke and Dan Connolly