> I don't see why it is an issue that some external identifiers don't
> translate to URIs. What complex logic is involved here? In RDF we should
> just add the plain identifier like we have it now as the default value,

If we say "since external IDs are in fact URIs, since they refer to
external databases, then let's mark them as URI property and render them
as full URI - i.e. let's instead of:

wd:Q1000336 wdt:P646 "/m/03pvzn"

say this:

wd:Q1000336 wdt:P646 <https://www.freebase.com/m/03pvzn>

This may make a lot of sense, since the interesting URL that people
would like to see may be the latter, and the former is kind of
chopped-off form of it we use for our internal purposes. OTOH, what if
it wasn't easy or possible to generate the latter from the former
automatically? Then we need some logic to figure that out.