CL-NTRIPLES provides a simple parser for the N-Triples data format as defined by the W3C for storing RDF/Semantic information. N-Triples is a line-based, plain text format for encoding an RDF graph.

Main entry function is PARSE-NT method that parses N-Triples from the given source. This method accepts a file pathname, an input stream, or a string.

Returns a list of triples consisting of three elements: subject, predicate, object. Subjects can be either an uriref or a nodeID. Objects can be of three types: uriref, nodeID or a literal. Depending on the type of the object it is encoded into an association list.

N-Triples data format standard definition is provided in the W3C documents:

Check also the Semantic Web page on CLiki.

Project page on Sourceforge.

Sample usage

CL-NTRIPLES Quickdocs is available through Quicklisp:

(ql:quickload :cl-ntriples)

CL-NTRIPLES was developed for a practical purpose of accessing the wealth of data accumulated by the DBPedia project. For example, let's query information about a Ukrainian city of Chernihiv (wiki, dbpedia):

(defvar page-url "")
(defvar *res* (nt:parse-nt (drakma:http-request page-url)))
;; *res* now contains a list of triples, let's query some predicates
;; for brevity, predicates will defined as variables

(defconstant +prop-area-total-km+ "")
(defconstant +rdf-label+ "")

;; querying predicates is now reduced to a simple function call:

;; what is the city area in km2?
(nt:predicate? *res* +prop-area-total-km+)
=> ((""
  ((:LITERAL-STRING . "79")
   (:URIREF . ""))))

;; how do Japanese call this city?
(predicate? *res* +rdf-label+ :lang "ja")
=> ((""
  (:LITERAL-STRING "???????" :LANG "ja")))


Package provides following functions:

  • PARSE-NT src Parses and returns a list of triples

  • PREDICATE? triples predicate &key lang data-type filters out triples with matching predicates. Additional parameters (lang and data-type) can be used to limit returned triples to those with matching language and data type specifiers.

  • LITERAL-STRING triple returns the literal-string value of the given triple.

Victor Anyakin <>
rdf, semantic web