SPARQLScript is already heavily used by the Pimp-My-API tool or the TwitterBot, but yesterday I added a couple of new features and finally had a go at implementing a (forward chaining) rule evaluator (for the reasons mentioned some time ago).
A first version ("LOD Linker") is installed on Semantic CB, with initially 9 rules (feel free to leave a comment here if you need some additional mappings). With SPARQLScript being a superset of SPARQL+, most inference scripts are not much more than a single INSERT + CONSTRUCT query (you can click on the form's "Show inference scripts" button to see the source code):
$ins_count = INSERT INTO <${target_g}>
CONSTRUCT {?res a foaf:Organization } WHERE {
{ ?res a cb:Company }
UNION { ?res a cb:FinancialOrganization }
UNION { ?res a cb:ServiceProvider }
# prevent dupes
OPTIONAL { GRAPH ?g { ?res a foaf:Organization } }
FILTER(!bound(?g))
}
LIMIT 2000
But with the latest SPARQLScript processor (ARC release 2008-09-12) you can run more sophisticated scripts, such as the one below, which infers DBPedia links from wikipedia URLs:
$rows = SELECT ?res ?link WHERE {
{ ?res cb:web_presence ?link . }
UNION { ?res cb:external_link ?link . }
FILTER(REGEX(?link, "wikipedia.org/wiki"))
# prevent dupes
OPTIONAL { GRAPH ?g { ?res owl:sameAs ?v2 } . }
FILTER(!bound(?g))
}
LIMIT 500
$triples = "";
FOR ($row in $rows) {
# extract the wikipedia identifier
$id = ${row.link.replace("/^.*\/([^\/\#]+)(\#.*)?$/", "\1")};
# construct a dbpedia URI
$res2 = "http://dbpedia.org/resource/${id}";
# append to triples buffer
$triples = "${triples} <${row.res}> owl:sameAs <${res2}> . "
}
#insert
if ($triples) {
$ins_count = INSERT INTO <${target_g}> { ${triples} }
}
(I'm using a similar script to generate foaf:name triples by concatenating cb:first_name and cb:last_name.)Inferred triples are added to a graph directly associated with the script. Apart from a destructive rule that removes all email addresses, the reasoning can easily be undone again by running a single DELETE query against the inferred graph.
I'm quite happy with the functionality so far. What's still missing is a way to rewrite bnodes, I don't think that's already possible. But INSERT + CONSTRUCT will leave bnode IDs unchanged, so the inference scripts don't necessarily require URI-denoted resources.
Another cool aspect of SPARQLScript-based inferencing is the possibility to use a federated set of endpoints, each processing only a part of a rule. The initial DBPedia mapper above, for example, uses locally available wikipedia links. However, CrunchBase only provides very few of those. So I created a second script which can retrieve DBPedia identifiers for local company homepages, using a combination of local queries and remote ones against the DBPedia SPARQL endpoint (in small iterations and only for companies with at least one employee, but it works).
