Connotea tags

The following SPARQL query returns the "tags" for a Connotea reference using the DOI as the search term (in this case doi:10.1007/bf02224026):

PREFIX dc: <http://purl.org/dc/elements/1.1/>
SELECT ?subject
WHERE {
  ?doi ?bnode 'doi:10.1007/bf02224026'
. ?connoteaURI ?identifier ?doi 
. ?item ?connotea ?connoteaURI
. ?item dc:subject ?subject
}

The graph being queried is this RSS file, which I've put in a triple store.
This query is simply following the path in the RDF from the DOI <connotea:idValue>10.1007/bf02224026</connotea:idValue>.

Note: One potential "gotcha" is that DOI's are not case sensitive, but SPARQL queries are (oh oh).