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Re: JSON Resource Description ?

From: Gregg Kellogg <gregg@greggkellogg.net>
Date: Fri, 8 Feb 2013 17:11:23 -0500
To: Kingsley Idehen <kidehen@openlinksw.com>
CC: "public-rdf-wg@w3.org" <public-rdf-wg@w3.org>
Message-ID: <64F59D3F-F0AB-4E3F-9CA4-4AFFBB569853@greggkellogg.net>
On Feb 8, 2013, at 12:55 PM, Kingsley Idehen <kidehen@openlinksw.com> wrote:

> On 2/8/13 3:35 PM, Gregg Kellogg wrote:
>> >From what I can see, JRD [1] is basically a JSON version of XRD [2]. I worked with XRD in the past, and it is useful for semantically describing the endpoints of a service, and the properties of URLs used by that service.
>> 
>> I don't really see that this could be considered as an alternative for JSON-LD, or a reasonably RDF representation.
>> 
>> Gregg Kellogg
>> 
>> [1]http://hueniverse.com/2010/05/jrd-the-other-resource-descriptor/
>> [2]http://docs.oasis-open.org/xri/xrd/v1.0/xrd-1.0.html
>> 
>> gregg@greggkellogg.net
> Gregg,
> 
> What makes the following impossible in JRD notation?
> 
> ##  RDF model statements in Turtle notation start ##
> 
> <> a <http://xmlns.com/foaf/0.1/Document> .
> <http://xmlns.com/foaf/0.1/Document> <http://xmlns.com/foaf/0.1/maker> <#i> .
> 
> ## End ##

My memory of XRD (the basis for JRD) is sketchy, but you might be able to describe this as follows:

<root  xmlns="http://docs.oasis-open.org/ns/xri/xrd-1.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <XRD>
    <Subject></Subject>
    <Link rel="http://www.w3.org/1999/02/22-rdf-syntax-ns#type" href="http://xmlns.com/foaf/0.1/Document"/>
  </XRD>
  <XRD>
    <Subject>http://xmlns.com/foaf/0.1/Document</Subject>
    <Link rel="http://xmlns.com/foaf/0.1/maker" href="#i"/>
  </XRD>
</root>

This is certainly not what XRD is intended for, however (at least IMO). I have not heard of anyone using XRD to describe RDF documents, in any case.

AFAIKT, the related JRD might be the following:

[
  {
    "subject": "",
    "links": {
      "http://www.w3.org/1999/02/22-rdf-syntax-ns#type": [ { "href": "http://xmlns.com/foaf/0.1/Document" } ]
   },
  {
    "subject": "http://xmlns.com/foaf/0.1/Document",
    "links": {
      "http://xmlns.com/foaf/0.1/maker": [ { "href": "#i" } ]
    }
  }
]

The fact that XRD/JRD include many other "properties" for things like Title, Alias, and Expires makes it seem special purpose for describing limited properties of resources needed to interact with them over HTTP. I expect that if someone looking for an XRD/JRD document saw it used to express general RDF, they wouldn't know what to do with it.

* Relations seem to be mostly used in the token space (e.g., "author", "copyright") and are not fully qualified.
* Links are intended to be used to identify related resources, not for describing purely semantic relationships such as rdf:type or foaf:maker. Certainly, these are IRIs and should be dereferencable, but in practice, dereferencing them is not necessary for general interaction.

It might be an interesting exercise for someone to fully spec out how to represent and interpret RDF in XSD/JRD, but the format is not optimized for that purpose.

If you have some experience in interpreting XRD as RDF, I'd be interested to hear about it.

Gregg

> -- 
> 
> Regards,
> 
> Kingsley Idehen	
> Founder & CEO
> OpenLink Software
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Received on Friday, 8 February 2013 22:12:06 GMT

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