> Blazegraph for example looks like does not
handle them out of the box

As Wikidata is an Open Wiki, I think we can't avoid the query engine having to deal with cycles from time to times. I can't imagine the Wikidata query engine having troubles with cycles. It must be robust.

2015-10-24 1:50 GMT+02:00 Stas Malyshev <smalyshev@wikimedia.org>:
Hi!

> least one Wikipedia) are considered to refer to equivalent classes on
> Wikidata, which could be expressed by a small subclass-of cycle. For

We can do it, but I'd rather we didn't. The reason is that it would
require engine that queries such data (e.g. SPARQL engine) to be
comfortable with cycles in property paths (especially ones with + and
*), and not every one is (Blazegraph for example looks like does not
handle them out of the box). It can be dealt with, I assume, but why
create trouble for ourselves?

> We also have/had cycles involving instance-of, which is definitely an
> error. ;-)

Right. So I think we need to mark properties that should not form cycles
with
https://www.wikidata.org/wiki/Q18647519 (asymmetric property) and have
constraints checking scripts/bots find out such cases and alert about them.
--
Stas Malyshev
smalyshev@wikimedia.org

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