RE: Model of Claims

Hi Manu

Thanks a lot for your clarifications.

What I still don't get:
> 
> > Shouldn't <did:example:ebfeb1f712ebc6f1c276e12ec21> be a named graph
> > containing something: like :Pat :ageOver 21 ?
> 
> <did:example:ebfeb1f712ebc6f1c276e12ec21> NQuads should be contained in
> a named graph (e.g. _:graph1), which contain stuff like :Pat :ageOver 21.

If you're using the notion of quads the element additional to the ones in the triple (the 4th element I N-Quads) would be the graph label. If the graph however is _:graph1 then imho that should be the value of the vc:claim property, so the dataset would look like this:

@prefix : <https://w3id.org/>.
@prefix ex: <http://vocab.example.org/> .
@prefix foaf: <http://xmlns.com/foaf/0.1/> .
@prefix xsd: <http://www.w3.org/2001/XMLSchema#>.

{
<http://example.gov/credentials/3732> a :Credential, :ProofOfAgeCredential;
    :issuer <https://dmv.example.gov>;
    :issued "2010-01-01"^^xsd:date;
    :claim _:graph1;
    :signature [
            a :LinkedDataSignature2015;
            :created "2016-06-18T21:10:38Z"^^xsd:dateTime;
            :creator <https://example.com/jdoe/keys/1>;
            :domain <json-ld.org>;
            :nonce "6165d7e8";
            :signatureValue "g4j9UrpHM4/uu32NlTw0HDaSaYF2sykskfuByD7UbuqEcJIKa+IoLJLrLjqDnMz0adwpBCHWaqqpnd47r0NKZbnJarGYrBFcRTwPQSeqGwac8E2SqjylTBbSGwKZkprEXTywyV7gILlC8a+naA7lBRi4y29FtcUJBTFQq4R5XzI="
    ].
}
_:graph1 {
[foaf:giveName "Pat"; foaf:familyName " Doe" ] ex:ageOver 21.
}

I'm not sure where the URI with the did-scheme would fit in, if it identifies the Pat Doe it could replace the blank node in _:graph1.

Cheers,
Reto

> -----Original Message-----
> From: Manu Sporny [mailto:msporny@digitalbazaar.com]
> Sent: Saturday, October 21, 2017 6:27 PM
> To: public-vc-wg@w3.org
> Subject: Re: Model of Claims
> Importance: High
> 
> On 10/21/2017 05:37 AM, Reto Gmür wrote:
> > Rereading vc-data-model I'm getting ab bit confused and I would
> > appreciate someone helping me understand.
> 
> I'll try, more below...
> 
> > In section 3.1 it seem that the claim is a graph.
> 
> It is.
> 
> > What confused me a bit is the statement that "To make the claim
> > verifiable, more information must be added to the graph of
> > information", because I would have imagined this graph being kind of
> > the payload of the verifiable claim with a separation of the graph
> > with the actual claim "Pat is over 21 and knows Sam, a student" from
> > the statements making the authorship of this claim verifiable.
> 
> Yes, your understanding of the underlying concept is correct.
> 
> > Since nested graphs are not yet supported in RDF I wanted to look at
> > the JSON-LD to see how this is solved (named graph or reification?).
> 
> I don't know what definition of "nested graph" you are using, but one could
> argue that RDF 1.1 Datasets fit some definition of "nested graph".
> We also support named/bnode graphs in JSON-LD.
> 
> A few data points:
> 
> 1. RDF 1.1 supports Datasets and JSON-LD builds on that concept (and
>    supports graph nesting as a part of the core JSON-LD data model,
>    which is RDF 1.1 compatible). Fundamentally, this means that
>    named graphs, and "graph nesting" (using a fairly loose
>    definition of that term) is supported. "claim" points to a
>    named/nested graph.
> 2. JSON-LD 1.1 will (hopefully) support graph containers as well. We've
>    added this support to the reference implementation of JSON-LD, which
>    is turned on in v1.1 processing mode.
> 
> > The JSON-LD however confused me even more. Looking at the example 12
> > in section 7.2.1 there is the triple:
> >
> > <http://example.gov/credentials/3732>
> > <https://w3id.org/credentials#claim>
> > <did:example:ebfeb1f712ebc6f1c276e12ec21> .
> 
> Yes, this example is misleading. It should be something like:
> 
> <http://example.gov/credentials/3732>
>   <https://w3id.org/credentials#claim>
>     _:graph1
>       _:DEFAULT_GRAPH .
> 
> <did:example:ebfeb1f712ebc6f1c276e12ec21>
>   <ex:somePredicate>
>     <ex:someObject>
>       _:graph1 .
> 
> That said, I'm afraid that doing so is going to confuse the hell out of most folks
> that don't know about the formal data model behind all of this stuff. Instead,
> we may want to express the examples in pictures rather than in NQuads.
> 
> > But I don't see any other triple describing
> > <did:example:ebfeb1f712ebc6f1c276e12ec21>.  The JSON-Key "ageOver"
> > doesn't resolves to a property.
> 
> Yes, it was just an example that we'll have to replace with a more correct one.
> 
> > Shouldn't <did:example:ebfeb1f712ebc6f1c276e12ec21> be a named graph
> > containing something: like :Pat :ageOver 21 ?
> 
> <did:example:ebfeb1f712ebc6f1c276e12ec21> NQuads should be contained in
> a named graph (e.g. _:graph1), which contain stuff like :Pat :ageOver 21.
> 
> We have added a new feature to JSON-LD that enables the expression of stuff
> like this... so you do something like this in the JSON-LD Context:
> 
> "claim": {
>   "@id": "https://w3id.org/credentials#",
>   "@container": "@graph"
> }
> 
> ... and that avoids us having to do something like this:
> 
> "claim": {
>   "@graph": [{
>     "id": "did:example:ebfeb1f712ebc6f1c276e12ec21",
>     "ageOver": 21
>   }]
> }
> 
> ... and instead we can do this sort of markup in JSON-LD, which is easy for web
> developers and formally correct:
> 
> "claim": {
>   "id": "did:example:ebfeb1f712ebc6f1c276e12ec21",
>   "ageOver": 21
> }
> 
> > A side question: what is the URI scheme "did"?
> 
> https://github.com/WebOfTrustInfo/rebooting-the-web-of-trust-

> fall2017/blob/master/topics-and-advance-readings/did-primer.md
> 
> > As you can see, I'm a bit lost...
> 
> Understandably, but I think I can clearly see why you were lost given your
> background and the hand waving we're doing on the formal stuff in the spec
> right now. Clearly, we need to fix that.. how would you propose we do that and
> keep "regular web developer" readability?
> 
> -- manu
> 
> --
> Manu Sporny (skype: msporny, twitter: manusporny, G+: +Manu Sporny)
> Founder/CEO - Digital Bazaar, Inc.
> blog: Rebalancing How the Web is Built
> http://manu.sporny.org/2016/rebalancing/

Received on Monday, 23 October 2017 20:39:22 UTC