Re: [TTL] Standardizing N-Triples

On Fri, Apr 1, 2011 at 8:34 PM, Steve Harris <steve.harris@garlik.com>wrote:

> On 2011-04-01, at 21:39, Nathan wrote:
>
> > Eric Prud'hommeaux wrote:
> >> * Alex Hall <alexhall@revelytix.com> [2011-04-01 15:29-0400]
> >>> On Fri, Apr 1, 2011 at 3:21 PM, Nathan <nathan@webr3.org> wrote:
> >>>
> >>>> Andy Seaborne wrote:
> >>>>
> >>>>> On 01/04/11 20:06, Nathan wrote:
> >>>>>
> >>>>>> Andy Seaborne wrote:
> >>>>>>
> >>>>>>> Are there examples of real worlds data that uses relative IRIs in
> >>>>>>> N-triples? If not, we could decide that theer is no base processing
> in
> >>>>>>> RDF-triples, absolute IRIs only.
> >>>>>>>
> >>>>>> How can we have @base processing if there are no directives or @base
> >>>>>> definitions? I'd strongly suggest we keep this to *IRI*s only.
> >>>>>>
> >>>>> The base is also set by where the file is read from.
> >>>>>
> >>>> Indeed, reliably though? for instance taking in to account the file
> being
> >>>> sent by email, being part of a zip archive, being in the message body
> of a
> >>>> PUT HTTP request, being in the body of a GET HTTP response with a
> >>>> Content-Location which differs from the effective request URI?
> >>>>
> >>>> Personally, I'd quite like that can of worms left closed for
> RDF-Triples :)
> >>>>
> >>> +1, but that reflects my bias as a developer, where often times all I'm
> >>> handed is an input stream with no information about where the content
> came
> >>> from.  It's nice to be able to use that information when it's
> available, but
> >>> I think it's extra complexity that's best left out of a simple format
> like
> >>> N-Triples.
> >> I'm a big fan of relocatable data and often take advantage of the
> >> ability to have a set of interrelated resources which can be moved
> >> from one location to another, or accessed both via e.g. http: and
> >> file: protocols. As an example, the SPARQL test suite manifests have
> >> relative references to the data, queries and expected results. This
> >> allows me to run the tests off the web or to download a tarball to an
> >> arbitrary location and run the tests. Relative references are a very
> >> handy element of web architecture.
> >> I expect that, if we demand absolute IRIs, folks will get around it
> >> with sed scripts and the like, but it will be an unnecessary pain.
> >
> > A very good point Eric, personally I hadn't came across this with
> N-Triples yet due to my own use-cases so far, although I guess in hindsight
> I can see uses for relative IRIs here too..
> >
> > Jury's out for me on this one I'm afraid, can't weigh up the cost /
> possible ambiguity of relative IRIs vs having a simple unambiguous format.
> >
> > Saying that.. I think we can reasonably expect people only to use
> relative IRIs on the web, and not come crying because they've used them in a
> base-less environment..!
>
> Most (all?) of the other RDF syntaxes already allow for relative IRIs, so
> it doesn't add any new requirement to a system that can already handle RDF.
>

The headache (for me at least) isn't resolving the relative IRIs, it's
picking a base IRI to resolve against when one isn't readily available.

I remember being surprised when parsing some Turtle with Jena to find that
it was emitting IRIs relative to the base directory from which I was running
the program.  That isn't to pick on Jena -- if you don't have a base IRI
then the user home directory makes as much sense as any other IRI you could
arbitrarily choose.  The point is that you have to make that choice, and not
all systems do so consistently.


>
> I agree with Eric that it's useful, I'm not sure whether there will be
> systems that only consume NTriples though.
>

Yes, Eric's point about portable archives with cross references between
documents is well taken.

-Alex