[Bigdata-developers] Handling of URL encoded strings in SPARQL queries submitted via HTTP

[Steve B. <ste...@va...>]

We have set up a Blazegraph instance at https://sparql.vanderbilt.edu 
and have loaded it with data.  Those data include multilingual 
translations of a controlled vocabulary.  The problem I'm having occurs 
when I send via HTTP to the endpoint a query that contains URL encoded 
literals that represent non-ASCII UTF-8 characters from other 
languages.  Here is a query that contains a literal with the character 
"ú" (URL encoded as %C3%BA):

SELECT DISTINCT ?term where {
?term <http://www.w3.org/2000/01/rdf-schema#isDefinedBy> 
<http://rs.tdwg.org/cv/status/>.
?term <http://www.w3.org/2004/02/skos/core#hiddenLabel> 'Común'.
}

If I paste the query into the Blazegraph SPARQL endpoint GUI box at 
https://sparql.vanderbilt.edu, I get a single result: the URI 
<http://rs.tdwg.org/cv/status/extant> as I should.  However, if I URL 
encode the query and sent it to the same Blazegraph endpoint via HTTP 
GET as:

https://sparql.vanderbilt.edu/sparql?query=SELECT%20DISTINCT%20%3Fterm%20where%20%7B%0A%3Fterm%20%3Chttp%3A%2F%2Fwww.w3.org%2F2000%2F01%2Frdf-schema%23isDefinedBy%3E%20%3Chttp%3A%2F%2Frs.tdwg.org%2Fcv%2Fstatus%2F%3E.%0A%3Fterm%20%3Chttp%3A%2F%2Fwww.w3.org%2F2004%2F02%2Fskos%2Fcore%23hiddenLabel%3E%20%27Com%C3%BAn%27.%0A%7D

there are no results.  I'm confident that the URL encoding is correct 
because if the same query is sent via HTTP GET to our old 
Callimachus-based endpoint, it returns the correct URI:

http://rdf.library.vanderbilt.edu/sparql?query=SELECT%20DISTINCT%20%3Fterm%20where%20%7B%0A%3Fterm%20%3Chttp%3A%2F%2Fwww.w3.org%2F2000%2F01%2Frdf-schema%23isDefinedBy%3E%20%3Chttp%3A%2F%2Frs.tdwg.org%2Fcv%2Fstatus%2F%3E.%0A%3Fterm%20%3Chttp%3A%2F%2Fwww.w3.org%2F2004%2F02%2Fskos%2Fcore%23hiddenLabel%3E%20%27Com%C3%BAn%27.%0A%7D

The problem appears to be with the endpoint's handling of the encoded 
literal characters.  If I change the literal to one that does not 
contain non-ASCII characters, such as "common" (a hidden label synonym 
of "Común"), so that the query is:

SELECT DISTINCT ?term where {
?term <http://www.w3.org/2000/01/rdf-schema#isDefinedBy> 
<http://rs.tdwg.org/cv/status/>.
?term <http://www.w3.org/2004/02/skos/core#hiddenLabel> 'common'.
}

the URL encoded HTTP GET:

https://sparql.vanderbilt.edu/sparql?query=SELECT%20DISTINCT%20%3Fterm%20where%20%7B%0A%3Fterm%20%3Chttp%3A%2F%2Fwww.w3.org%2F2000%2F01%2Frdf-schema%23isDefinedBy%3E%20%3Chttp%3A%2F%2Frs.tdwg.org%2Fcv%2Fstatus%2F%3E.%0A%3Fterm%20%3Chttp%3A%2F%2Fwww.w3.org%2F2004%2F02%2Fskos%2Fcore%23hiddenLabel%3E%20%27common%27.%0A%7D

produces the correct result.

I am at a loss as to where to go with this as far as trouble-shooting is 
concerned.  It's possible that there is some incorrect server 
configuration setting that I don't know about.  I suppose it's also 
possible that it's a bug.  This is a rather serious problem for us 
because we have significant multilingual data in the triplestore and 
users need to be able to search against it.

Steve Baskauf

-- 
Steven J. Baskauf, Ph.D., Senior Lecturer
Vanderbilt University Dept. of Biological Sciences

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