=Paper=
{{Paper
|id=Vol-449/paper-16
|storemode=property
|title=SPARCool: SPARQL made easy
|pdfUrl=https://ceur-ws.org/Vol-449/Challenge7.pdf
|volume=Vol-449
|dblpUrl=https://dblp.org/rec/conf/esws/Passant09
}}
==SPARCool: SPARQL made easy==
<pdf width="1500px">https://ceur-ws.org/Vol-449/Challenge7.pdf</pdf>
<pre>
              SPARCool: SPARQL made easy

                                 Alexandre Passant

                       Digital Enterprise Research Institute,
                       National University of Ireland, Galway
                           alexandre.passant@deri.org



      Abstract. This paper introduces the motivations and technical details
      behind SPARCool, a web service that provides an easy way to run
      SPARQL queries on the Web by calling a simple URL pattern1 .

      Key words: SPARQL, Linked Data, SPARCool, JSONP


1   Motivations

Thanks to the Linking Open Data2 community project, million of resources,
identified by their URI, are now described on the Web thanks to RDF(S)/OWL
technologies. To efficiently take advantage of it and go further than simple brows-
ing, developers must use either SPARQL or RDF(S)/OWL APIs to query and
use this data. Yet, it can be complex for Web developers that are not necessarily
aware of such languages. SPARCool3 aims to solve this gap by providing a way to
let people easily run SPARQL queries on any URI that follows the Linked Data
principles4 [1] without learning the SPARQL syntax, and then build applications
using the query answers.


2   Using SPARCool

In order to run SPARQL queries with SPARCool, one just have to call the
URL pattern http://sparcool.net/format/predicate[;l=lang]/URI, that
is translated into a SPARQL query applied to the URI given as a parameter. The
format parameter indicates the required output and can be (1) XML SPARQL
Query results, (2) JSON SPARQL Query results, (3) HTML view of the results,
either plain-HTML (for a single result) or using a <ul/> list (for multiple results)
and (4) a redirect to the first query of the answer, for instance for hyperlinks
or images. The predicate must be written using a QName syntax and a set of
prefixes are supported by SPARCool, while the lang parameter is optional.
1
  The work presented in this paper has been funded in part by Science Foundation
  Ireland under Grant No. SFI/08/CE/I1380 (Lı́on-2).
2
  http://linkeddata.org
3
  http://sparcool.net
4
  Especially the three first ones, are the fourth one is not a requirement for SPARCool.
2      Alexandre Passant

    While the two first types of results (XML and JSON serialization of SPARQL
query results) imply additional work if developers want to integrate it into web-
pages, the HTML view and the redirect can be used to directly expose results
in HTML pages. Especially, SPARCool also supports JSONP5 callbacks, so that
the HTML results of SPARCool calls can be embedded directly in (X)HTML
pages on client side, without having to face AJAX cross-domain security issues.
That way, it enables to construct dynamic and constantly up-to-date webpages:
if the information about a particular URI changes (e.g. a foaf:homepage value),
the webpage will be automatically adapted.
    Examples of SPARCool queries, using various result formats, can be found
on the service website: http://sparcool.net.

3   Query translation
http://sparcool.net/j/foaf:name;l=fr/http://example.org/Bob#b will be
translated into the following query6 , and results will be serialized in JSON.
FROM <http://example.org/Bob#b>
SELECT ?value
WHERE {
  <http://example.org/Bob#b> rdf:label ?value .
  FILTER (lang(?value) = ’en’)
}
   Since the FROM parameter is applied to the same URI used in the query
pattern, this URI must follow the Linked Data principles, especially being deref-
erencable and returning (machine-readable) information about itself, whatever
the RDF serialization it (RDFa, RDF/XML, etc.).

4   Implementation
SPARQL is provided thanks to a PHP script (less than 100 lines of code) that
translates the called URI (thanks to Apache RewriteRule) to a SPARCool object
that contains the generated SPARQL query and additional parameters (output
format and JSONP callback if any). The query is then launched using roqet
(part of Redland7 ) and the results are intercepted by the SPARCool object that
sets the proper content-type and returns the results in the browser.

References
1. Tim Berners-Lee. Linked Data. Design issues for the world wide web, World Wide
   Web Consortium, 2006. http://www.w3.org/DesignIssues/LinkedData.html.

5
  http://bob.pythonmac.org/archives/2005/12/05/remote-json-jsonp/
6
  Prefixes ommited
7
  http://librdf.org

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