Special characters in URI in SPARQL

Question

Hi all,

Given a dataset with URIs of the format http://example.com/a:someA/b:someB, I want to use a Sparql PREFIX to shorten the queries. When I run on Virtuoso:

PREFIX mysite:<http://example.com/>
select * where { mysite:a:something/b:somethingelse ?p ?o }

I get the error 37000 Error SP030: SPARQL compiler, line 2: Undefined namespace prefix at '' before '?p'

Clearly, the problem is the character : in the query. What is the best solution in this case? Should I remove all the : from the URIs to make them usable in SPARQL?

Thanks for any hint,

Mulone

Accepted Answer

In SPARQL 1.1 you can write:

PREFIX mysite:<http://example.com/>
select * where { mysite:a:something\/b:somethingelse ?p ?o }

Note in front of the /. Multiple colons are allowed in prefixed names, only the first separates the prefix from the local part. These changes were in a later last call draft, and are in the final publication, to align SPARQL and the standardisation of Turtle, which is work-in-progress by the RDF working group. Virtuoso coverage will vary.

The SPARQL validator at http://www.sparql.org/query-validator.html is up to date with these changes.

Answer 2

You can escape such characters using a backslash:

PREFIX mysite:<http://example.com/>
select * where { mysite:a\:something\/b\:somethingelse ?p ?o }

If for some reason your SPARQL engine does not accept this (escaping chars like this is a SPARQL 1.1 feature, not all engines will have implemented it), you can either choose to just use the entire URI in the query for such cases:

PREFIX mysite:<http://example.com/>
select * where { <http://example.com/a:something/b:somethingelse> ?p ?o }

...or you can of course modify your data (if it's your own data to edit) so that you don't use such chars in URIs.

Special characters in URI in SPARQL

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