Turtle Trouble (was: Re: [protocol] Patch formats)

This email's been in my head for awhile (too long probably) and this patch
thread tipped it to the point of my fingers typing what's in my brain. :)
So here goes...

First (and foremost, maybe), I actually really like Turtle. :)

However....it requires a way of thinking that the prevailing systems
(non-graph databases, browsers, JS runtimes, etc) don't currently think in.

We've addressed that in the data model by preferring / promoting the
JSON-LD representation in examples--while still providing the Turtle
representation for those that support it.

Where things fall down for me (at least) are with the protocol
specification--which, being based on LDP (which is otherwise quite
fabulous) comes with the requirement that:
http://www.w3.org/TR/ldp/#h4_ldprs-HTTP_GET
> ...MUST respond with a Turtle representation...when the request includes
an Accept header specifying text/turtle
> ...SHOULD respond with a text/turtle...whenever the Accept request header
is absent.
> ...MUST respond with a application/ld+json representation...when the
request includes an Accept header specifying application/ld+json

What this means practically (afaik) is that an Annotation API server MUST
be able to transform their stored info into both Turtle and JSON-LD
(regardless of which was sent in).

There aren't (that I've found) terribly many Turtle-to-JSON-LD
transformation libraries. I've used this one (recently relicensed to Apache
License 2.0) with varied success:
https://github.com/warpr/turtle-to-jsonld

However, that (plus it's dependencies) provides a transformation to a
JSON-LD format that may actually not be what one wants in the end, and then
requires yet-more transformation and more understanding of the "meta model"
by the API server (and/or database) to move between the formats.

Here's where this hits the PATCH format options....

On Sat, Jun 6, 2015 at 12:57 AM, Ivan Herman <ivan@w3.org> wrote:

>
> > On 05 Jun 2015, at 20:51 , Robert Sanderson <azaroth42@gmail.com> wrote:
> >
> >
> > In reading back through the discussion at the face to face about the
> protocol draft, it was noted that there are many possible patch formats,
> including LDPatch, JSON Patch, Sparql Update, diff and so on.  All would be
> possible to use, and some easier in different circumstances.
> >
> > Do we want to:
> >
> > a)  Specify one as a requirement (MUST) and let the others be usable
> (MAY)
> > b)  Not specify any as a requirement and just remain silent on which one
> to use.
> >
> > If B is the preference, then we would need to decide how the server
> advertises which of the PATCH formats it implements so that clients can
> determine how (if at all) they can interact.
> >
> > My preference is A, and to pick LDPatch (by reference) as part of the
> LDP stable of specifications, but what do people think?
>
> My preference is also A, although the issue of advertising may still be
> relevant. ('may'. We may decide not to address this issue.)
>

If the database or API server you are building supports a graph-based "meta
model" then supporting the transformation between Turtle and JSON-LD or
LDPatch or anything else triple-based is "just some more code." :)

However, if your database does not (most databases don't...even if they
"speak" JSON), then handling LDPatch is an even farther reach than
supporting Turtle.

Here's an LDPatch example for those who are curious:
http://www.w3.org/TR/ldpatch/#full-example


>
>  > Benjamin suggested at the F2F a preference for JSON Patch, for example.
>

Good memory, Rob! :)

The preference is completely along these lines:
 - most available tooling supports JSON
 - "understanding" the `-LD` bit of JSON-LD is at some level "optional" (at
least for storage, basic parsing, and transportation)
 - if a PATCH format is chosen, it should be equally "dumb" (in the best
possible way) ;)

Because:
 - if developers can deal with annotations as JSON (+/- the `-LD` knowhow),
they can start using annotation data now with very little additional effort
added to their stack
 - if developers *want* to use PATCH, having the option of a patch format
equally as "dump" (just dealing with keys and values, not triples), means
(again) that they can start with (nearly) what they already know and have.

Here's the list of examples from the JSON Patch (RFC 6902) spec:
http://tools.ietf.org/html/rfc6902#appendix-A


>
> I do not have a strong feeling on whether it is json patch or ldpatch, not
> really familiar with the details and certainly no experience. I. I have a
> slight preference to JSON, however; as far as I can see, LDPatch is based
> on a turtle syntax, and we did make a decision to put JSON-LD forward as
> our primary syntax in the model (in view of our constituency). In this
> respect JSON patch seems to be more in line with the rest.
>

I suppose it comes down to "cutting with the grain" of what's already in
place--with the option to "be smarter" if you know how to be. :)

I'm all for having Turtle as an *option* and (if I have that) also having
LDPatch as an *option.*

However, if these become mandatory, I fear we're cutting off a large part
of the potential integration, implementation, and consuming developers.

I'd love to see annotation data as widely used as feeds were "back in the
day."

I think it's possible, but (at least right now) I think that means keeping
the "smarter" graph stuff as optional bits and not required defaults--as
they are in LDP.

Ideally, we find a way to spec our Annotation API that is at once "simple"
and also LDP compatible.

Is that feasible?

Did any of this make sense? :)

Thanks for listening regardless. ;)

Cheers,
Benjamin
--
Developer Advocate
http://hypothes.is/


>
> (Maybe there is an Abis possibility: require JSON and LDPatch? Or is that
> too much?)
>
> Ivan
>
> >
> > Thanks!
> >
> > Rob
> >
> > --
> > Rob Sanderson
> > Information Standards Advocate
> > Digital Library Systems and Services
> > Stanford, CA 94305
>
>
> ----
> Ivan Herman, W3C
> Digital Publishing Activity Lead
> Home: http://www.w3.org/People/Ivan/
> mobile: +31-641044153
> ORCID ID: http://orcid.org/0000-0003-0782-2704
>
>
>
>
>