Update: We seem to have an issue with the 4store hosting the dataset, so the data is stale since the end of February. Update 2: All should be back to normal and in sync. Please comment on this post if you spot any issue, or general slowliness.

Last year, we got OpenLink and Talis to crawl BBC Programmes and provide two SPARQL end-points on top of the aggregated data. However, getting the data by crawling it means that the end-points did not have all the data, and that the data can get quite outdated -- especially as our programme data changes a lot.

At the moment, our data comes from two sources: PIPs (the central programme database at the BBC) and PIT (our content mangement system for programme information). In order to populate the /programmes database, we monitor changes on these two sources and replicate them on our database. We have a small piece of Ruby/ActiveRecord software (that we call the Tapp) which handles this process.

I made a small experiment, converting our ActiveRecord objects to RDF and hooking an HTTP POST or an HTTP DELETE request to a 4store instance for each change we receive. This means that this 4store instance is kept in sync with upstream data sources.

It took a while to backfill, but it is now up-to-date. Check out the SPARQL end-point, a test SPARQL query form and the size of the endpoint (currently about 44 million triples).

The end-point holds all information about services, programmes, categories, versions, broadcasts, ondemands, time intervals and segments, as defined within the Programme Ontology. All of these resources are held within their own named graph, which means we have a very large number of graphs (about 5 million). It makes it far easier to update the endpoint, as we can just replace the whole graph whenever something changes for a resource.

This is still highly experimental though, and and I already found a few bugs: some episodes seem to be missing (for example, some Strictly Come Dancing episodes are missing, for some reason). I've also encountered some really weird crashes of the machine hosting the end-point when concurrently pushing a large number of RDF documents at it - I still didn't succeed to identify the cause of it. To summarise: it might die without notice :-)

Here are some example SPARQL queries:

  • All programmes related to James Bond:
PREFIX po: <http://purl.org/ontology/po/>
PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>
SELECT ?uri ?label
WHERE {
  ?uri po:category 
    <http://www.bbc.co.uk/programmes/people/bmFtZS9ib25kLCBqYW1lcyAobm8gcXVhbGlmaWVyKQ#person> ; rdfs:label ?label
}
  • FInd all Eastenders broadcast dates after 2009-01-01, along with the type of the version that was broadcast:
PREFIX event: <http://purl.org/NET/c4dm/event.owl#> 
PREFIX tl: <http://purl.org/NET/c4dm/timeline.owl#> 
PREFIX po: <http://purl.org/ontology/po/> 
PREFIX xsd: <http://www.w3.org/2001/XMLSchema#>
SELECT ?version_type ?broadcast_start
WHERE
{ <http://www.bbc.co.uk/programmes/b006m86d#programme> po:episode ?episode .
  ?episode po:version ?version .
  ?version a ?version_type .
  ?broadcast po:broadcast_of ?version .
  ?broadcast event:time ?time .
  ?time tl:start ?broadcast_start .
  FILTER ((?version_type != <http://purl.org/ontology/po/Version>) && (?broadcast_start > "2009-01-01T00:00:00Z"^^xsd:dateTime))}

PREFIX po: <http://purl.org/ontology/po/>
PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>
PREFIX mo: <http://purl.org/ontology/mo/>
PREFIX foaf: <http://xmlns.com/foaf/0.1/>
PREFIX event: <http://purl.org/NET/c4dm/event.owl#>
PREFIX tl: <http://purl.org/NET/c4dm/timeline.owl#>
PREFIX owl: <http://www.w3.org/2002/07/owl#> 
SELECT DISTINCT ?programme ?label
WHERE {
  ?event1 po:track ?track1 .
  ?track1 foaf:maker ?maker1 . ?maker1 owl:sameAs <http://www.bbc.co.uk/music/artists/67f66c07-6e61-4026-ade5-7e782fad3a5d#artist> .
  ?event2 po:track ?track2 .
  ?track2 foaf:maker ?maker2 . ?maker2 owl:sameAs <http://www.bbc.co.uk/music/artists/fb7272ba-f130-4f0a-934d-6eeea4c18c9a#artist> .
  ?event1 event:time ?t1 .
  ?event2 event:time ?t2 .
  ?t1 tl:timeline ?tl .
  ?t2 tl:timeline ?tl .
  ?version po:time ?t .
  ?t tl:timeline ?tl .
  ?programme po:version ?version .
  ?programme rdfs:label ?label .
}