qcrumb.com

Qcrumb.com is a query evaluation service for remote data sources. You can link to results (which are cached for a day or so).

The service supports SPARQL and XQuery.

SPARQL Form

You can specify data sources using FROM/FROM NAMED clauses which the query processor loads during query evaluation.

The query processor can optionally take into account rules (roughly equivalent to Datalog).

Query: PREFIX sdmx-measure: <http://purl.org/linked-data/sdmx/2009/measure#> PREFIX dcterms: <http://purl.org/dc/terms/> PREFIX eus: <http://ontologycentral.com/2009/01/eurostat/ns#> PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> PREFIX qb: <http://purl.org/linked-data/cube#> PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#> SELECT ?time ?value ?geo FROM <http://estatwrap.ontologycentral.com/data/tsieb020> FROM <http://estatwrap.ontologycentral.com/dic/geo> WHERE { ?s qb:dataSet <http://estatwrap.ontologycentral.com/id/tsieb020#ds> . ?s dcterms:date ?time . ?s eus:geo ?g . ?g rdfs:label ?geo . ?s sdmx-measure:obsValue ?value . FILTER (lang(?geo) = "en") } ORDER BY ?geo
Rules (optional): (e.g., http://qcrumb.com/rdfs++.rules)
Result format (alternatively, use an Accept header)

You can access data sources using the expath http-client extension.

2012-02-29: Added functx extension
2012-02-29: Added XQuery engine
2011-12-02: Results expire after one day; uses "Vary: Accept" header now for correct caching
2011-09-12: Added more caching
2011-08-17: Added support for text/nx result format (for use with NxParser)
2011-07-16: Added support for rules (currently in Jena Rule format), included a set of rdfs++ rules
2011-02-11: Returns gziped results if requested; empty accept header returns text/plain rather than an exception
2011-01-06: HTTP POST available
2011-01-05: Now uses a Access-Control-Allow-Origin header to enable Cross-Origin Resource Sharing.

We currently use ARQ for SPARQL and BaseX for XQuery.

The latest version of this query processor is available as free online service at http://qcrumb.com/.