Hi! > Anyone an idea why this query has a trouble when I add the OPTIONAL keyword? > > *http://tinyurl.com/pgsujp2* > > Doesn't look much harder than the queries in the examples.
It's not because it's harder. It's because ?head can be unbound, and you can not apply label service to unbound variables. If you drop ?headLabel then it works. It is a downside of the label service, not sure yet how to fix it (feel free to submit the Phabricator issue, maybe myself or somebody else has an idea later). -- Stas Malyshev smalys...@wikimedia.org _______________________________________________ Wikidata mailing list Wikidata@lists.wikimedia.org https://lists.wikimedia.org/mailman/listinfo/wikidata
