Linking Open Government Data

Source Code and Resources

SparqlProxy is a TWC LOGD service:

• source code: http://code.google.com/p/data-gov-wiki/source/browse/trunk/web/logd.tw.rpi.edu/ws/sparqlproxy.php
• all related XSL files: http://logd.tw.rpi.edu/ws/sparqlproxy/
• tutorial: how to use SparqlProxy
• report issues at TWC LOGD issue tracker.

RESTful Service Interface Description

Parameter	Status	Description
service-uri	stable	URI of SPARQL service.
query	stable	SPARQL query string
query-uri	stable	URI of SPARQL query. Note you can only use one of "query-uri" and "query" because they are mutually exclusive.
output	stable (optional)	the output format. Default is xml. All values a listed as below: xml => SPARQL/XML sparqljson => SPARQL/JSON exhibit => EXHIBIT/JSON gvds => GoogleViz/JSON csv => CSV html => HTML tablerow => Table(Row) tablecol => Table(Col) To keep backward comparability, both "sparqljosn" and "sparql" can be used to output SPARQL/JOSN format.
callback	experimental (optional)	callback function name. This param is only applicable to two output formats: exhibit, sparqljson
tqx	experimental (optional)	for google visluziation api only. e.g. version:0.6;reqId:1;responseHandler:myQueryHandler
refresh-cache	experimental (optional)	SparqlProxy use a cache by default. User may opt out (avoid caching) by setting "refresh-cache=on" in service request
textoutput	experimental (optional)	set "text/plain" as content-type in HTTP response header, so users can view the result in browser. To enable it, add "textoutput=yes" in service request
ui-option	experimental (optional)	SparqlProxy allow users to show the query of SPARQL query result. To enable it, add "ui-option=query" in service request

Example Usage

• Example 1: Standard SPARQL protocol. Use string value for "query" parameter. It will output XML by default. "service-uri" is set to DBPedia.
  http://logd.tw.rpi.edu/ws/sparqlproxy.php?query=SELECT+%3Fs+%3Fp+%3Fo++WHERE+{%3Fs+%3Fp+%3Fo}+limit+10%0D%0A&service-uri=http%3A%2F%2Fdbpedia.org%2Fsparql
• Example 2: Use online SPARQL query. Use the URL of SPARQL file for "query-uri" parameter, and use "gvds" for "output" to output Google Visualization Compatable JSON ).
  http://logd.tw.rpi.edu/ws/sparqlproxy.php?query-uri=http%3A%2F%2Flogd.tw.rpi.edu%2Fquery%2Fstat_list_ten_triples.sparql&service-uri=http%3A%2F%2Fdbpedia.org%2Fsparql&output=gvds
• Example 3: Generate HTML fragment. Use the URL of SPARQL file for "query-uri" parameter, and use "tablecol" for "output" to output a fragment of html table to be embedded in dynamic HTML page).
  http://logd.tw.rpi.edu/ws/sparqlproxy.php?query-uri=http%3A%2F%2Flogd.tw.rpi.edu%2Fquery%2Fstat_list_ten_triples.sparql&service-uri=http%3A%2F%2Fdbpedia.org%2Fsparql&output=tablecol
• Example 4: refresh cache. Since query results may be cached to improve performance, users may add "refresh-cache=on" to refresh query results
  http://logd.tw.rpi.edu/ws/sparqlproxy.php?query-uri=http%3A%2F%2Flogd.tw.rpi.edu%2Fquery%2Fstat_list_ten_triples.sparql&service-uri=http%3A%2F%2Fdbpedia.org%2Fsparql&output=tablecol&refresh-cache=on

A: We maintain two sparqlproxy instances on LOGD server: http://logd.tw.rpi.edu/sparql dedicates to the LOGD sparql endpoint, and http://logd.tw.rpi.edu/ws/sparqlproxy.php allows users to access other sparql endpoints. Users may download the sparqlproxy code and install an instance on their own computer, allowing external users to access their internal triplestores.