String addition in ARQ?

Hi,
I've been trying to figure out an issue with addition of strings in
SPARQL. According to the DAWG evaluation test at:
http://www.w3.org/2009/sparql/docs/tests/summary.html#functions-plus-1
"1" + "2" != "12", but ARQ run via Fuseki-1.0.1 would seem to disagree. I
also tried running the following similar query on dbpedia
# :x6 :p "1" ; :q "2" .
SELECT ?x ?y ( ?x + ?y AS ?sum)
WHERE

VALUES( ?x ?y ) {
( "1" "2" )

ORDER BY ?x ?y ?sum

and it seems to agree with the W3C expected results. Is this a bug in ARQ?

Thanks,
Tim