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Re: (proposal) was Re: defn of Named Graph

From: Pat Hayes <phayes@ihmc.us>
Date: Thu, 3 Oct 2013 21:53:55 -0500
Cc: <public-rdf-wg@w3.org>
Message-Id: <85404CDE-9700-48AB-82C1-200032031794@ihmc.us>
To: Markus Lanthaler <markus.lanthaler@gmx.net>

On Oct 3, 2013, at 10:01 AM, Markus Lanthaler wrote:

> On Friday, September 27, 2013 6:35 PM, Pat Hayes wrote:
>> Let me (only just now surfacing from a few days off-web) suggest:
>> (6) Keep the idea but modify the terminology. As Andy points out,
>> "Named Graph" already has too much baggage (and in any case is weirdly
>> misleading in two ways). But we already have some useful terminology in
>> the LC specs: Concepts 1.1 defines "RDF Source" as a nameable thingie
>> that emits or embodies RDF (and might be labile). So lets take this and
>> run with it, and talk about "fixed RDF Source" as a non-labile species
>> of RDF source, and say that the graph name denotes that. Or even just
>> forget about the "fixed" part:
>> "3. We note that RDF Datasets can be used to state which triples are in
>> certain RDF Sources.
>> 4. We define a class (eg rdf:BasicDataset) of the Datasets which have
>> those semantics."
>> This avoids all the issues that Andy raises, and has the advantage that
>> it has a very smooth segway into datase... sorry, things like datasets
>> but which are allowed to be updated.
> +1 but...
> ... as I've just re-read the definition of RDF source in Concepts, it
> appears that its definition is wrong (or at least inconsistent):
>   We informally use the term RDF source to refer to a persistent yet
> mutable
>   source or container of RDF graphs. An RDF source is a resource that may
> be
>   said to have a state that can change over time. A snapshot of the state
> can
>   be expressed as an RDF graph
> So a RDF source may return *multiple* RDF graphs, i.e., a dataset

No, it can return different graphs at different times, but it always returns a single graph. The dataset equivalent would be a thing like a dataset but where the inner graphs were RDF sources, so that we would have 'named sources' rather than named graphs. Which is exactly what we need to make the idea of 'naming' to work properly. There is currently no terminology for this dataset-source notion, so we will have to invent one or adapt a current term to this wider use. 


> but at the
> same time it is possible to express a snapshot as a *single* RDF *graph*.
> Thus, we should either define something like a "RDF graph source" or say
> that a snapshot of a RDF source can be expressed as a RDF dataset.
> If we are going to use this reuse terminology, I think we should also name
> the classes accordingly. Something like rdf:RdfGraphSource and potentially
> also something like rdf:TripleSource or just rdf:RdfSource.
> --
> Markus Lanthaler
> @markuslanthaler

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Received on Friday, 4 October 2013 02:54:42 UTC

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