Hi Adrian,

the query.wikidata.org service run on Blazegraph that implements OpenRDF. So it's strange to obtain two different behaviours. However some triplestore accepts also weak syntax (e.g. with parenthesis) and may be the case.

To make the query run in Jena you can just change "((str ?year) AS ?year)" into "((str ?year) AS ?yearString)".

Best,

Alessio

2017-08-18 14:47 GMT+02:00 Adrian Bielefeldt <Adrian.Bielefeldt@mailbox.tu-dresden.de>:

Hello everyone,

I was wondering about the example query "Average number of children per year". When I try to parse this using OpenRDF, I get the error "projection alias 'year' was previously used", in Jena "Variable used when already in-scope: ?year in ((str ?year) AS ?year)". This seems to be in line with the sparql specifications.

However, query.wikidata.org accepts it just fine. So I was wondering how exactly this kind of situation is being resolved.

Greetings,

Adrian


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