Re: the necessity of describing responses in-band

On Oct 8, 2015, at 8:23 AM, Markus Lanthaler <markus.lanthaler@gmx.net> wrote:
> 
>> On 6 Okt 2015 at 14:17, Ruben Verborgh wrote:
>> I've written a blog post that describes the necessity
>> of describing responses in-band:
>>    http://ruben.verborgh.org/blog/2015/10/06/turtles-all-the-way-down/
> 
> Nice post! One question I have is why you blanked the URL bar in the second
> screenshot? Even if the resource itself isn't self-describing, the client
> would still know how it retrieved it, no?
> 
> I have to say though, that I'm not a big fan of exchanging named graphs as
> they have undefined semantics...

As I recall, it was expected that other specifications might define the semantics of names graph related to their use. It was RDF that did not define any semantics. I think, in this case, using named graphs in the context of LDP/Hydra could be given semantics. For example, the graph name <http://www.w3.org/ns/hydra> might be defined to represent API provisioning triples using the Hydra spec. A non-Hydra aware client wouldn't know what to do with them, but if the Hydra spec defined such usage, then it could have meaning for a Hydra-aware client.

Gregg

>> 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. 
> 
> 
>> Seemed much more logical to make it the name of the graph,
>> would give the term "named graph" a more logical meaning.
>> And if you want a graph that has nothing to do with the name,
>> just pick a different name then anyway.
>> 
>>> But do you think that using quads would come at the risk of
> interoperability
>>> issues?
>> 
>> Hard to predict, but I don't think so.
> 
> With the current state of affairs I think using datasets on the public Web
> is basically made impossible. The only thing that's defined, is that if a
> client expects a RDF graph but gets a dataset instead, it should use the
> dataset's default graph and ignore the named graphs.
> 
> 
>>> What would happen if someone did a LOAD operation of one of these quads
>>> documents into a store?
>> 
>> Nothing bad, it seems. Do you think of scenarios where things go wrong?
> 
> As it is undefined, it depends solely on the implementation.
> 
> 
> --
> Markus Lanthaler
> @markuslanthaler
> 
>

Received on Friday, 9 October 2015 03:15:41 UTC