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).

To speed up access to remote data source, please make sure that the sources have caching enabled (setting Cache-Control: public and Expires header).

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
Rules (optional)
(e.g., http://qcrumb.com/rdfs++.rules)
Result format (alternatively, use an Accept header)

XQuery Form

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

Query

News

2012-07-06
Update to ARQ 2.9.2, speed-up recovery from exceptions, added text regarding caching.
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.

Notes

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/.