Re: multiple-graph example in the Primner

* Sandro Hawke <sandro@w3.org> [2013-12-07 11:01-0500]
> On 12/07/2013 10:17 AM, Yves Raimond wrote:
> >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
> 
> Oh, that's pretty.    Yes, something like that.  More below.
> >with an additional statement <http://example.org/bob> a eg:WebSource?
> 
> I'd propose it's the dataset (<>) that's the WebSource, not /bob
> that's the WebSource.   Pat can correct me, but my sense is that
> nothing we say about the thing denoted by the graph name can affect
> what we're saying about the associated graph or how they are
> connected.   To say something about how the graph name's denotation
> and the associated graph are related, we have to say something about
> the dataset itself.
> 
> On the image itself, I'd suggest a few tweaks:
> 
>    - move the "Graph Name" bubbles to the bottom of their sections,
> and label them with some black text, saying "Graph Name: " before
> the graph name.   Or maybe "Named Graph, with name="
>    - similarly label the default graph, at the bottom, with the
> black text "Default Graph".
>    - change the styling of the default graph's
> http://example.org/bob bubble to be like the other subjects, in this
> case using a document/web-page icon like http://sfxvisions.com/SFX/wp-content/uploads/2012/11/text-file-icon.png,
> with the subject URL being http://example.org/bob
>    - Use that same icon for the <> a eg:WebSource triple

I don't know if any "artwork" from the 1999 spec persists in our specs,
but if so, you could use render IRIs as simple ellipses for compatibility.

     - Render IRIs as simple ellipses.


> Now I'm struggling with how to connect the two uses of
> http://example.org/bob.   One option is to put it on the border like
> MonaLisa, making it both a subject in the DG and the denotation of
> the NG.   Another option is to put a dotted arc between them, with a
> clever label I can't quite think of.   Another option is to just
> have them be visually close enough of the screen that it's obvious
> they are the same string.
> 
> Another issue with the diagram is that by using rectangles, it's a
> style that only works for trivial datasets.     Using coloring or
> tagging of the arcs, or having them in layers, allows for arbitrary
> datasets.   So I have some concern that if people learn to visualize
> it this way, they'll get stuck when they try to think of, for
> instance, a subject being shared between 3 or more different NGs.

JJC found 126 venn diagrams that explored permutations of
intersections of six sets. I'm sure folks can just use those
for more complex visualizations...
http://www.combinatorics.org/files/Surveys/ds5/VennTriangleEJC.html


>      -- Sandro
> 
> 
> >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
> >>>>>>>
> >>>>>>>>]]
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>------------------------------------------------------------
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> >>>>>>>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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-- 
-ericP

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Received on Saturday, 7 December 2013 16:32:53 UTC