Re: Blank Nodes Re: Toward easier RDF: a proposal

Henry you mentioned keys earlier, I should be clearer and say that by
incomplete I mean in terms of key attributes for equality checking. For a
blank node of type Person it's not likely the attribute "ancestor" would be
a key, that information could be missing, it's more likely something like
nationality and social security number for example would be relied upon.

It's definitely useful to work with partial information, but I'd type it as
such. A blank node with a numerator property but not a denominator property
I would allow to exist but I wouldn't type it as a Fraction.

Just FYI, in Swift there is what you describe, they're called "optionals".
There can be a value there of a specific type, or nothing, and yes you do
end up with lots of if statements but they're useful.

Anthony

On Mon, Dec 3, 2018 at 2:33 PM Henry Story <henry.story@bblfish.net> wrote:

>
>
> > On 3 Dec 2018, at 23:10, Anthony Moretti <anthony.moretti@gmail.com>
> wrote:
> >
> > Cheers for agreeing William. On the topic of incomplete blank nodes
> Henry I'd give them another type, the partial address example you give I'd
> give the type AddressComponent, or something to that effect. I could be
> wrong, but it's not a valid Address if it's a blank node and no other
> information in the graph completes it.
>
> So saying that you know a Person without specifying all their family tree
> all the way to
> Adam and Eve would be incomplete information then! 8‑0
>
> A database can get corrupted and information go missing. Knowing that
> there was a relation
> from a to b to c without knowing b but knowing that b lived at a certain
> street, might
> allow you to find the missing information.
>
> This is exactly the role existential quantifiers play. They allow us to
> make a statement
> without specifying the object precisely, but require us then to be
> committed to accepting
> that the graph will be true when the blank node is replaced at one point
> by the correct
> name.
>
> In a way you can get this in OO programming by allowing every object's
> value to be null,
> but then you end up with a lot of if then statements, unless you have some
> monadic null.
> In a way I find RDF here a lot more satisfactory as it takes incomplete
> information into
> account.
>
> Henry
> >
> > Anthony
> >
> > On Mon, Dec 3, 2018 at 1:56 PM William Waites <wwaites@tardis.ed.ac.uk>
> wrote:
> > > standards like schema:PostalAddress should possibly define relevant
> > > operations like equality checking too.
> >
> > Exactly.
> >
> >
>
>