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Re: [JSON] Initial comments

From: Pierre-Antoine Champin <pchampin@liris.cnrs.fr>
Date: Thu, 24 Feb 2011 23:55:44 +0100
Message-ID: <4D66E1F0.8070409@liris.cnrs.fr>
To: Thomas Steiner <tomac@google.com>
CC: "nathan@webr3.org" <nathan@webr3.org>, RDF WG <public-rdf-wg@w3.org>
Hi all,

Thomas: I have heard that argument against RDF already: too many 
syntaxes confuse the potential users. This has been used to argue 
against the endorsement of Turtle by the WG. Although I see the point of 
this argument, I think the multiplicity of syntaxes emphasizes that RDF 
is *not* a file format, but a data model. So I think we can live with 
that -- but surely, we need to get better at explaining *why* we have so 
many syntaxes, and *when* to use which syntax...

Nathan: I agree with you that there are two ways to consider JSON: easy 
to parse for machines, and easy to write/generate for web developers. 
However I'm not sure the first criterion is relevant here. As Yves 
stresses out in another mail, the problem with RDF syntaxes is not so 
much parsing them than re-constructing the graph structure from the tree 
structure given by the parser.

My guess is that the human-oriented JSON syntax should aim at making it 
easy to produce.

To make RDF easy to consume, we don't need syntaxes (we already have a 
dead-simple syntax: N-Triples), what we need is APIs.

   pa


On 02/24/2011 10:07 AM, Thomas Steiner wrote:
> Nathan, all,
>
>> One is to create a JSON serialization of RDF, capable of serializing all the
>> RDF concepts (anything Turtle will be able to), an optimized machine to
>> machine RDF transportation format.
>
>> The second need is much more complex, to create a JSON format which allows
>> people to publish and work with linked/web data easily.
>
> Assuming I got Nathan mostly right, honestly I'm not entirely sure
> whether I fully agree with his ideas. He basically writes, and correct
> me if I'm wrong, that there is a need for two media types, let's call
> them:
>
> application/rdf-humans+json
> application/rdf-robots+json
>
> I'm quite new to the whole Semantic Web scene (so I beg your pardon
> should I write something stupid and thanks for correcting me in either
> case), however, from the beginning was under the impression that this
> whole scene is not the easiest to enter. As most beginners, I was
> first confronted with RDF/XML. I learnt to prefer Turtle very quickly,
> though. OK, so far, so good. Now, let's consider what this WG (among
> other things of course) tries to enable: to make John Doe Web
> developer grasp the principles of RDF. A Web developer who might be a
> jQuery god (or in the worst case a W3Schools alumnus), but never have
> heard of the Semantic Web. Basically someone who loves JSON, because
> it enables him to easily mash-up several APIs to a cool Web
> application. Long story short, imagine for a minute our community
> confronting this guy with the following made up introduction:
>
> ===
> OK, so, the Semantic Web. You know, triples and such. Subject,
> predicate, object. It's totally easy, look at Open Graph from Facebook
> [sample here]. Open Graph is just the beginning. Look, there's more
> [try to "wow" John Doe Web developer and show him DBpedia,
> MusicBrainz, explain Linked Data, etc.]. Keen to use it: great! OK, so
> there's RDFa for marking up your own content. Look, it's totally
> simple [try to make it look simple]. OK, now, so, you want to use the
> X API [cool Web 3.0 read/write-enabled API]. It's totally easy with
> JavaScript. It's all JSON. It gives you application/rdf-robots+json.
> You can even write to the service using PUT or POST [many real-world
> APIs will even use GET, but let's ignore this for a moment]. You can
> use application/rdf-humans+json. Or you can use
> application/rdf-robots+json, but you don't really want to. Look,
> there's this application/rdf-humans+json2application/rdf-robots+json
> service. Yeah, it even has has a SOAP API for legacy reasons. Oh, and
> for the same reasons, it's also able to return RDF/XML. RDF/XML? Oh,
> you know, that's just another serialization. We used to use it in the
> old days, before the Semantic Web was cool. OK, there're still some
> services around that just speak RDF/XML, but you know, actually, they
> should just move to application/rdf-humans+json. Or
> application/rdf-robots+json. Or both. Hell, simply don't use them.
> ===
>
> OK, most of this is heavily exaggerated, but I guess I made my point
> clear. If we want people to use RDF in JSON, heck, it better be easy.
> Ideally it would fit on a napkin or a beer coaster.
>
>> I'm personally convinced that if we try to mix the two we'll be here for
>> years and tbh, we'll simply fail. So, my first request would for people to
>> either agree or disagree with what I've said above, put it to a vote and
>> move on with doing the two distinct things.
> I'm pretty sure Nathan has very good technical reasons for bringing up
> the idea of two formats. I bring up the above perceptional reasons
> against the technical reasons, and fair enough, Nathan's, for sure,
> costed much more work brain-wise, and all respect for that. Simply,
> first and above we should put the user. Make it fit on a napkin, make
> it fit on a beer coaster, or see it fail with the John Doe Web
> developers of this world. My point of view.
>
>> JSON is so popular because it's focussed on simple key/value objects, with
>> limited value types, essentially a JSON object is as simple as:
>>
>>   { "name": "nathan", "gender": "unknown" }
>>
>> and people can work with that data by doing:
>>
>>   print( obj.name );
>>   obj.gender = "male";
> All agreed.
>
>> I'd place that as a constraint, that if we make it any more complicated than
>> that, people simply won't use it.
> All agreed. But, where do you put subjects?
>
>>  From a linked/web data angle, the most critical parts are to give things
>> IRIs as identifiers, and to have a shared understanding of properties,
>> perhaps better said as use IRIs to name properties.
>>
>> At the bare minimum that's all we need to get by, thus I'd also place these
>> constraints on what we do, that those two needs must be fulfilled.
> Agreed.
>
>> To me, the above simply points to needing a way to specify @id's and some
>> kind of data transformation map for these objects, essentially a simple map
>> from property name to property URI
>>
>>   "name" ->  "http://xmlns.com/foaf/0.1/name"
>>   "gender" ->  "http://xmlns.com/foaf/0.1/gender"
> This sounds straight-forward, however, as soon as you start mixing
> ex:name and foaf:name (and this will happen), you need the concept of
> namespaces (call it CURIEs if you want). I have seen foaf.name or
> foaf_name in some of the proposed JSON formats (was it JRON?), and I
> fear, there's no way around sticking to the idea of namespace.
>
>> The next question is whether that map needs to be in with the JSON, or
>> outwith it (in an external document) - again this seems like an easy design
>> trade-off to make, just as with CSS for HTML an external document makes a
>> lot of sense, especially when you consider the common JSON use-cases (like
>> twitter api), and it also allows bootstrapping on to existing data sources
>> via a Link header or suchlike.
> Not sure I get this, but I think, you're suggesting to introduce
> something like a @profile document as in RDFa, or at least a
> well-known URI where such document would be available, and not be
> touched unless the modification was downwards-compatible. I'm not
> against this idea, thinking of, e.g., well-known Link relations (e.g.,
> @rel="license").
>
>> Additionally, there is often a need to provide custom datatypes and to place
>> restrictions on values for validation and the like, as with xsd and owl,
>> which imho points to the need for something like JSON-Schema.
> And this is where most Web developers (in my humble opinion) will
> start to hate us. JSON is so successful because it limited itself to
> the things that are available in almost every programming language,
> arrays, integers, floats, booleans, objects (did I forget something?).
> Introducing long ints, short ints, this kind of things, just makes
> things brittle, strictly tightened, SOAPish. The Web is just not like
> that.
>
>> That's about it I'm afraid, something to discuss.
> Very happy to get it started :-)
>
> Best,
> Tom
>
Received on Thursday, 24 February 2011 22:56:18 GMT

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