W3C home > Mailing lists > Public > public-linked-json@w3.org > July 2013

RE: Input needed from RDF group on JSON-LD skolemization

From: Markus Lanthaler <markus.lanthaler@gmx.net>
Date: Tue, 2 Jul 2013 10:40:22 +0200
To: <public-linked-json@w3.org>
Message-ID: <00f401ce76ff$cc9296a0$65b7c3e0$@lanthaler@gmx.net>
On Tuesday, July 02, 2013 12:22 AM, David Booth wrote:
> On 07/01/2013 10:33 AM, Markus Lanthaler wrote:
> > On Monday, July 01, 2013 4:07 PM, David Booth wrote:
> >> Yes, I am suggesting that the feature of permitting blank nodes in
> >> that JSON-LD position -- the position that would result in blank
> >> predicates
> >> in the RDF model -- be removed.   Users would instead be required to
> >> use URIs in those cases instead of blank nodes.
> >
> > Or, more likely, they would just not map those properties at all and the
> > data would be lost due to that.
> 
> I was referring to the JSON-LD document authors.  Do you mean that you
> think authors would would only include those data elements in their
> JSON-LD if they could use blank node predicates?

Yes


> > For example, you may have a JSON representation of a blog post and
> > all its comments:
> >
> > ...
> > comments: [
> >    {
> >      text: ...
> >      author:
> >        {
> >          name: ...
> >          .. other properties you are interested in ...
> >        }
> >    }
> > ]
> >
> > You could extract the all persons by mapping name to foaf:name etc.
> > and all other properties to blank nodes:
> >
> > {
> >    "@context": {
> >      "@vocab": "_:",
> >      "name": "http://xmlns.com/foaf/0.1/name",
> >      ...
> >    }
> > }
> >
> > and then just filter out the nodes which have a foaf:name.
> >
> > If you wouldn't map all other properties to blank nodes you wouldn't get
any
> > triples at all as we ignore unmapped properties (and their complete
> > subtrees).
> 
> AFAICT we seem to be talking about different things.  I am trying to
> address the problem of what should be the standard RDF interpretation of
> a JSON-LD document -- not what a particular client might choose to use
> or ignore from that document.

I don't think so. It may be the author of the document who decides to just
expose parts of a JSON-LD document as "RDF". I anticipate that there will be
quite some APIs that will gradually transform the JSON APIs to JSON-LD APIs.
Without allowing bnode-predicates this becomes considerably harder to do as
the example illustrates.


> Any client may ignore any information it
> wants, but it is important that different JSON-LD standards-compliant
> parsers, both parsing the same JSON-LD document in an attempt to obtain
> the JSON-LD standards-compliant RDF interpretation of that JSON-LD
> document, should obtain the same set of RDF triples (except for blank
> node labels and possibly data type conversion).

And that's the case right now. Every compliant JSON-LD parser is required to
produce exactly the same generalized RDF dataset.


> One possible way to achieve this is for the JSON-LD spec to disallow
> blank nodes in positions that would be mapped to RDF predicates.  I
> believe this means disallowing blank nodes as keys.  Instead, a user
> would have to use a relative URI, a Compact URI or an absolute URI.
> 
> Are there any important use cases that would be significantly impacted
> by this change?

Didn't I just answer that question?



--
Markus Lanthaler
@markuslanthaler
Received on Tuesday, 2 July 2013 08:40:57 UTC

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