Datalink vocabulary

[Markus Demleitner]

Hi Pat,

On Tue, Sep 23, 2014 at 09:29:55AM -0700, Patrick Dowler wrote:
> General question about this field: how should a client interpret a
> null value for the semantics field? Normally this means "unknown" but

My take: The interpretation is "the data provider messed up".  That's
because it's not unlikely that that's what happened (and for that
reason I'm against overloading NULL as self; it's just too easy to
get a NULL by accident and self is too important a category).

I'm not sure whether we should formally require non-NULL here; on the
one hand, requiring it would let a validator (*obligatory bambi eyes
all around*) flag a hard error if it is.  On the other hand, data
providers will mess it up anyway, and clients should somehow
gracefully fail on NULLs here (I'd say we should recommend just
swallowing rows with NULL semantics; that'd let us use this as an
extension mechanism, too, if need be).

Cheers,

        Markus