File | Date | Author | Commit |
---|---|---|---|
src | 2012-12-16 |
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[e0f222] fixed minor issues, updated documentation |
.hgtags | 2012-12-16 |
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[dd405e] Added tag rel2012.12.16 for changeset 5b85ed78d5e1 |
README.md | 2015-07-31 |
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[96c272] renamed readme to .md |
cl-ntriples.asd | 2012-12-16 |
![]() |
[e0f222] fixed minor issues, updated documentation |
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.
CL-NTRIPLES 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 "http://dbpedia.org/data/Chernihiv.ntriples")
(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+ "http://dbpedia.org/property/areaTotalKm")
(defconstant +rdf-label+ "http://www.w3.org/2000/01/rdf-schema#label")
;; querying predicates is now reduced to a simple function call:
;; nt:predicate? TRIPLES PREDICATE &key LANG DATA-TYPE
;; what is the city area in km2?
(nt:predicate? *res* +prop-area-total-km+)
=> (("http://dbpedia.org/resource/Chernihiv"
"http://dbpedia.org/property/areaTotalKm"
((:LITERAL-STRING . "79")
(:URIREF . "http://www.w3.org/2001/XMLSchema#int"))))
;; how do Japanese call this city?
(predicate? *res* +rdf-label+ :lang "ja")
=> (("http://dbpedia.org/resource/Chernihiv"
"http://www.w3.org/2000/01/rdf-schema#label"
(:LITERAL-STRING "チェルニーヒウ" :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.