Re: n-quads & Turtle Levels

On Wed, 2012-05-30 at 10:27 +0100, Andy Seaborne wrote:
> On 30/05/12 00:52, Sandro Hawke wrote:
> > On Mon, 2012-05-28 at 14:01 +0100, Andy Seaborne wrote:
> >>
> >> On 28/05/12 13:11, Ivan Herman wrote:
> >>>> I don't see why. The only spec that has any reason to mention quads
> >>>> is N-Quads. (Well, JSON-LD may too but it uses a definition that's
> >>>> different from Sandro's.) Other uses of quads are implementation
> >>>> strategies and those don't belong into the specs.
> >>> Correct. My question was whether this WG would define NQuads as well
> >>> or not. If we do define NQuads (and I do not believe this has been
> >>> decided pro or con) then we have to properly define Quads and that in
> >>> relations to any formalism we have on named graphs. If we decide that
> >>> NQuads are not to be formally defined by this WG, then indeed this
> >>> section may become unnecessary.
> >>>
> >>> Ivan
> >>>
> >>
> >> Firstly, I think we really ought to define N-Quads; it's in use and
> >> extending the N-Triples work to N-Quads is valuable.
> >
> > I thought so too -- which is why I wrote it up for the rdf-spaces
> > document, but the discussion with Manu in the last telecon gave me
> > second thoughts.
> >
> > He was arguing how bad it was to be proliferating syntaxes.
> There are two facets to proliferation:
> 1/ RDF/XML / RDFa / turtle syntaxes have no family relationship.
> 2/ Turtle / N-Triples do have a family relationship (same DNA - IRIs and 
> <....>, literals in long form are in common).
> (and "we" expect Turtle for humans and N-Triples for dumps?)
> > I'm very
> > sensitive to his criticism: in the OWL WG, having OWL 2 QL, EL, and RL,
> > with the Direct and RDF-Based Semantics, ... it all made so much sense
> > and seemed so necessary.  Outside the OWL WG?  Not so much.)
> >
> > So I was thinking we might frame it as:
> >
> > Turtle Level 0 --- canonical n-triples
> > Turtle Level 1 --- what we're now calling Turtle
> > Turtle Level 2 --- something like Trig that's a superset of Turtle
> A dataset is a set { default graph , (IRI, graph) }
> A graph is not a dataset in the same way a triple or an IRI is not a graph.

I happen to disagree with this.  I think the relationship is much closer
to   graph : dataset :: file : tar file

Or better:     graph : dataset  ::   character : string

In some languages (eg C, C++) the type for character and string are
completely different.  In others (Python, Javascript), there are no
characters -- you just use strings of length 1.     

I think the Python/JS approach works in RDF APIs and languages, too,
saying that when you want to work with a graph, just use a dataset that
doesn't happen to have any named graphs.

It's with these glasses that I think a turtle document can/should just
be an instance of our multiple-graph syntax which doesn't happen to have
any named graphs.
> > I'm not sure N-Triples as currently defined even needs a name in the new
> > regime; it could be Level 0.1 I guess.
> N-triples is a dump format that systems like to use.  It is used, it has 
> utility.  It needs a name - it has a name - and it needs a content type.
> > So, the problem with N-Quads is that it doesn't fit into this scheme.
> > It's an extension to a subset, forking the neat sequence.  I dunno; just
> > a thought.   There's a lot to be said for having some trivial quad
> > syntax.
> >
> > Another thought about canonical syntaxes: let's specify a single TAB
> > between terms.  And we'll require any tabs inside strings be escaped in
> > this canonical form.  That way a TSV parser will correctly put the terms
> > into the right columns, even for N-Quads, where the graph name goes
> > after the literal.   (I think I'd put a tab before the trailing dot, so
> > the last field doesn't end up in the last column's data.)  I believe
> > this gets us past grep(1) all the way to join(1) and friends (sort, cut,
> > uniq, ...).   Not that I've used join(1) in the past 20 years....
> I agree with Richard.
> And I would add it invalidates existing data for no benefit to users.
> While grep etc exist, are they the tools of choice of a majority of RDF 
> applications?  I doubt it - or rather I hope not.

I thought I heard consensus or near-consensus that we should define a
canonical form of N-Triples.

I guess not.

   -- Sandro

Received on Wednesday, 30 May 2012 11:17:35 UTC