W3C home > Mailing lists > Public > public-rdf-wg@w3.org > December 2013

Re: multiple-graph example in the Primner

From: Yves Raimond <yves.raimond@bbc.co.uk>
Date: Sat, 7 Dec 2013 15:17:03 +0000
To: Sandro Hawke <sandro@w3.org>
CC: Kingsley Idehen <kidehen@openlinksw.com>, "public-rdf-wg@w3.org" <public-rdf-wg@w3.org>
Message-ID: <1386429423.754.1.camel@RD000190>
On Sat, 2013-12-07 at 10:12 -0500, Sandro Hawke wrote:
> On 12/07/2013 09:54 AM, Kingsley Idehen wrote:
> > On 12/7/13 8:28 AM, Sandro Hawke wrote:
> >> Kingsley Idehen <kidehen@openlinksw.com> wrote:
> >>> On 12/7/13 7:54 AM, Sandro Hawke wrote:
> >>>> Pat, I agree with you about the situation except I believe there's a
> >>> way out, which is why I stopped objecting back when we were making
> >>> these decisions.  The way out is to define some vocabulary which
> >>> communicates from Alice to Bob what kind of dataset semantics Alice is
> >>> using.   That vocabulary doesn't need to be defined in a W3C
> >>> recommendation to work.  So the primer just needs to posit that such
> >>> vocabulary might exist, and give the example as a hypothetical.
> >>> Alternatively, we could define that vocabulary (non rec track) right
> >>> now and use it in the primer with a caution that this is only one of
> >>> many possible ways to use datasets.
> >>>>        - Sandro
> >>> Yes, a vocabulary can be used to solve the problem. Net effect, we
> >>> still
> >>> don't need a confusing and contradictory example in the spec :-)
> >>>
> >> I don't see any need for it to be confusing or contradictory. I'd
> >> suggest we choose the semantics where URLs used as graph names denote
> >> sources which yield the associated graph.   I believe that's what the
> >> overwhelming majority of readers will expect, so when they read the
> >> example they will feel reassured that they can do what they
> >> expected.   The only confusing thing will be our caveats, if we're
> >> not careful.
> >>
> >>    - Sandro
> > The following examples will lead to confusion:
> >
> > ## Relative Resource URL serving as a Named Graph IRI
> > <>
> > {<#s> <#p> <#o> } .
> >
> > ## variation of the above
> >
> > <.ttl>
> > {<#s> <#p> <#o> } .
> >
> > ## Absolute Resource URL serving as a Named Graph IRI
> >
> > <http://example.org/example.ttl>
> > {<#s> <#p> <#o> } .
> >
> > ## 3 Named Graphs where two are derived from Resource URLs and one is
> > an inferred Default (or System) Named Graph which maybe be associated
> > with
> > ## {<#s> <#p> <#o> } .
> > ## OR
> > ## a Union of the Default, <.ttl>, and <> .
> >
> > <.ttl>
> > {<#s> <#p> <#o> } .
> > <>
> > {<#s> <#p> <#o> } .
> >
> >
> > All of the examples above cover implementation and usage scenarios
> > that are best covered via related specs such as SPARQL (for querying)
> > and concrete syntaxes (NQuad, TriG etc.).
> >
> > It is best for the RDF spec, primer, and related collateral to focus
> > on RDF semantics for triples based structured data representation. All
> > examples should be simple for the reader to understand and follow :-)
>
> I don't think the example has to be that complicated.   I think if we
> just include in the TrigG details a triple like "<> a eg:WebSource" (and
> mention that's a suitably defined class) then we're technically correct,
> and users aren't particularly confused. (I'm happy to have it be
> rdf:WebSource defined in a WG Note, if we want).
>
> If the Primer also included a diagram of the dataset being discussed --
> drawn as an RDF graph of the merge of the two named graphs and the
> default graph, color coded and segmented by their names -- then I think
> it wouldn't be confusing at all.

Like
https://dvcs.w3.org/hg/rdf/raw-file/default/rdf-primer/example-multiple-graphs.jpg with an additional statement <http://example.org/bob> a eg:WebSource?

Yves

>
>        -- Sandro
>
>
> >
> > Kingsley
> >>
> >>> Kingsley
> >>>> Pat Hayes <phayes@ihmc.us> wrote:
> >>>>> On Dec 5, 2013, at 4:53 AM, Guus Schreiber <guus.schreiber@vu.nl>
> >>>>> wrote:
> >>>>>
> >>>>>> In the telecon yesterday there were some flames about the graph
> >>>>> metadata examples in the Primer.
> >>>>>> My position:
> >>>>>> - There needs to be at least one example triple in the Primer in
> >>>>> which a graph name is being used. Dropping this completely is for
> >>> the
> >>>>> editors a no-go.
> >>>>>
> >>>>> Including such an example is a no-go for me. I will formally object
> >>> (or
> >>>>> protest, or register a dissent, I am not sure of the exact W3C
> >>> process
> >>>>> involved here) if the WG publishes any document which implies that
> >>> such
> >>>>> usage is in any way supported by the RDF 1.1 specifications. That is
> >>>>> *exactly* the semantic stumbling-point at which we were unable to
> >>>>> provide any semantics for datasets. RDF 1.1 does NOT imply in any
> >>> way
> >>>>> that the use of a graph-name in an RDF triple can or should be
> >>>>> understood to refer to the graph. On the contrary, it explicitly
> >>> denies
> >>>>> the validity of such an assumption.
> >>>>>
> >>>>>> - We are happy to consider other examples. Please suggest.
> >>>>>> - We're happy to include other/updated caveats
> >>>>>>
> >>>>>> Current phrasing included below. Text suggestions very much
> >>>>> appreciated!
> >>>>>> Guus
> >>>>>>
> >>>>>> From
> >>> https://dvcs.w3.org/hg/rdf/raw-file/default/rdf-primer/index.html#subsection-multiple-graphs

> >>>
> >>>>> :
> >>>>>> [[
> >>>>>> We can write down triples that include a graph name, for example:
> >>>>>>
> >>>>>>    <http://example.org/bob> <is published by> <http://example.org>.
> >>>>>>    <http://example.org/bob> <has license>
> >>>>>>        <http://creativecommons.org/licenses /by/3.0/>.
> >>>>>>
> >>>>>> These two triples could be interpreted as license and provenance
> >>>>> information of the graph http://example.org/bob.

> >>>>>> NOTE
> >>>>>> RDF does not define the way in which the graph name and the graph
> >>> are
> >>>>> related. It is therefore up to application developers to decide how
> >>> to
> >>>>> interpret such triples.
> >>>>>
> >>>>> That does not deal with the central difficulty. RDF is intended for
> >>> use
> >>>>> in publishing data on the open Web. The issue involved here is, if
> >>>>> Alice publishes an RDF dataset, and Bob reads it, how can Bob know
> >>>>> whether a graph name used in RDF in the datset should be interpreted
> >>> as
> >>>>> referring to the graph it names? And the clear, unambiguous answer
> >>>>> given by our RDF specs is, Bob cannot know this. There is no way
> >>>>> specified to record or transmit this information through RDF or any
> >>>>> means usable by an RDF engine. Alice might conform to the metadata
> >>>>> useage needed by PROV, and Bob might read this and interpret it
> >>>>> differently, without failing in any way to conform to RDF. So as far
> >>> as
> >>>>> RDF is concerned, this usage is invisible. Vague references to
> >>>>> "application developers" does not deal with this issue.
> >>>>>
> >>>>> Pat
> >>>>>
> >>>>>> ]]
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>> ------------------------------------------------------------
> >>>>> IHMC                                     (850)434 8903 home
> >>>>> 40 South Alcaniz St.            (850)202 4416   office
> >>>>> Pensacola                            (850)202 4440   fax
> >>>>> FL 32502                              (850)291 0667 mobile
> >>>>> (preferred)
> >>>>> phayes@ihmc.us       http://www.ihmc.us/users/phayes

> >>>>
> >>>>
> >>
> >>
> >>
> >
> >
>
>



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Received on Saturday, 7 December 2013 15:17:36 UTC

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