Can somebody please explain (in simple terms)
what's the difference
between "all" and "truthy" RDF dumps? I've read the explanation
available on the wiki  but I still don't get it.
Technically "truthy" is the set of statements with best non-deprecated
rank for the property. Semantically, it is the value you most likely
expect as the answer to a simple question "what is X of Y", like "what
is the population of London" or "who is the wife of the US president?"
If I'm just a user of the data, because I want to
information about a particular item and link items with other
graphs... what am I missing/leaving-out by using "truthy" instead of
Historical data - i.e. current population vs. all historic population
figures, current spouse vs.all previous marriages, current head of state
vs. list of all people occupying the office. Some other data, possibly,
such as official name vs. alias (provided that is expressed as a
property), commonly accepted value vs. alternative possibilities, etc.
A practical example would be appreciated since it will
things, I suppose.
Current (as in, latest/best available for now) population of London
would be found as "truthy" value (wdt), all other population figures -
e.g. historical figures - will be under "all" (p/ps/psv).