Hi!
The way that updates work *in all systems* (polling
small lists of
recent changes at intervals and hoping that this leads to a complete
change history), it seems quite possible that such systems will
sometimes miss an update, at least in the long run and under varying
conditions (high server load, network troubles, update script down for a
while, whatever). Insufficient update frequency is maybe not the biggest
problem here (it should be in the range of one to a few minutes for all
of the services).
Very important point with which I agree - it is completely possible that
update polling misses an update, WDQS is no exception and it usually
does not treat it as a problem, as the next update can fill up the
missed one. However the ultimate truth source is on the wikidata site
only. Beware of the caches though - if you ask for the same data on the
same URL twice, I think you can get the same result even if the
underlying data changed in the meantime.
--
Stas Malyshev
smalyshev(a)wikimedia.org