Re: the necessity of describing responses in-band

>
> On 7 Okt 2015 at 23:00, Ruben Verborgh wrote:
> > On 7 Okt 2015 at 22:13, John Walker wrote:
> >> Another point I'd like to raise is the use of quads rather than triples.
> >> As you are most likely aware there are no agreed formal semantics for
> RDF
> >> datasets [1].
> >
> > Yes and that's quite horrible.
> > anybody knows why the graph IRI is only a syntactical construct?
>
> It is the graph's name but it's semantics are not clear. It is undefined
> whether the name denotes the graph or not. The reasons for that are because
> the RDF WG at the time couldn't find consensus. Graph names have
> historically used for different purposes (timestamp graphs, record
> provenance, slice data by subject, ...) and it wasn't clear which to elect
> to the "winner" and what would break by doing so.


There's quite a long W3C note on this topic here:
http://www.w3.org/TR/rdf11-datasets/

My sense is that the semantics decided on were really the only reasonable
choice.
Intuitively, we may want to say that a graph name denotes the graph; but
that
stipulation is not required for many (any?) use cases, is fairly
ontologically heavy,
and breaks a large swath of existing usage.

To see the ontological weight, note that the RDF 1.1 Semantics allows
interpretations
with arbitrary mappings between IRI's and Resources in the universe. The
suggested
graph naming semantics requires:

  - All allowable universes of resources must contain all the graphs in a
dataset.
  - Certain IRIs must map to those graphs, simply by virtue of their
position in the
    dataset's quads; no other IRIs exhibit similar behavior.

This rules out a wide swath of otherwise allowable interpretations.
Reasoners are put
in the position of inferring the graph-ness of the resources denoted by the
graph
names, and presumably determining whether their other classes are disjoint.

Concretely, it rules out many interpretations that are in common use: e.g.
the
pattern of grouping statements relevant to a resource <a> in a graph named
<a>.

In short, it would be Range-14 all over again: "wait, that can't be Moby
Dick, it's
clearly just the _graph about Moby Dick_."

I'll pass. :)

- Tom