Re: Yet another serialization format?

On 06/29/2011 04:50 PM, Kingsley Idehen wrote:
> On 6/29/11 3:28 PM, Markus Lanthaler wrote:
>>> Let take the the Facebook URL: http://graph.facebook.com/kidehen, that
>>> resolves to a JSON based graph (not linked data since the properties
>>> and
>>> values are all literals and URIs do not resolve to representations of
>>> their referents).
>> What exactly do you mean by "URIs do not resolve to representations 
>> of their referents"? I'm a bit confused..
>
> I mean just that an HTTP scheme based Identifier that resolves to a 
> Representation of its Referent. The Representation takes the form of 
> an EAV/SPO graph pictorial (Attribute=Value pairs that coalesce around 
> a Named Subject) with serializations formats being negotiable.

I can attempt a slightly more fuzzy, less technically correct, but 
perhaps easier to grasp, explanation for what I believe Kingsley's 
statement meant:

There's a Linked Data object that mentions a Thing. That Thing is 
referred to by a web page (the Referent) for which you can get a 
Representation. You can use HTTP to resolve the web page's URI and get 
back a graph of information that will, somewhere in it, refer to the 
Thing. You can use HTTP to negotiate for various kinds of 
Representations of the same graph (eg: RDFa, JSON-LD, etc).

The whole point is so that, given a Linked Data object, you can always 
"follow your nose" (resolve a URI) when trying to find out what the 
values and properties in the object mean and where they uniquely reside 
on the web. It also allows you to make sure that you're talking about 
the same Thing as someone else who might happen to make statements about 
that Thing using Linked Data.

Now, more specifically towards your question, when Kingsley was saying 
that the JSON graph that is found here:

http://graph.facebook.com/kidehen

{
    "id": "605980750",
    "name": "Kingsley Uyi Idehen",
    "first_name": "Kingsley",
    "middle_name": "Uyi",
    "last_name": "Idehen",
    "link": "http://www.facebook.com/kidehen",
    "username": "kidehen",
    "gender": "male",
    "locale": "en_US"
}

Is not Linked Data, he simply meant that the properties "id", "name", 
etc, and the values "605980750", "kidehen", etc. are literal strings, 
they are not URIs and they have no Linked Data context that could map 
them to URIs (the "@context" concept in JSON-LD). That means that their 
meaning cannot be somehow derived by using the information itself. You 
need some other document or piece of information to be able to 
understand their meaning. In order to "link" your data to other data on 
the web, you must have identifiers and properties that are URIs that can 
be followed to retrieve Representations of the graphs that refer to them 
and give them meaning.

If we want to make the property "name" meaningful in the Linked Data 
world, it should be part of a vocabulary that explains what a "name" is. 
Then "name" should be mapped to a URI that resolves to that vocabulary. 
If we want to be able to refer to identifier "605980750" elsewhere, then 
it should be replaced with a URI that can be resolved to a graph that 
refers to that identifier and, likely, provides more information about it.

-- 
Dave Longley
CTO
Digital Bazaar, Inc.
http://digitalbazaar.com