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RE: second review of json-ld

From: Markus Lanthaler <markus.lanthaler@gmx.net>
Date: Fri, 29 Mar 2013 18:28:54 +0100
To: "'Gregg Kellogg'" <gregg@greggkellogg.net>, "'Sandro Hawke'" <sandro@w3.org>
Cc: "'W3C RDF WG'" <public-rdf-wg@w3.org>
Message-ID: <00c601ce2ca2$e4b9a9a0$ae2cfce0$@lanthaler@gmx.net>
My preferred "fix" for the JSON-LD specification to be silent about this as
I've already said in the past. What happens when there are multiple embedded
JSON-LD documents is, IMO, completely application specific. Of course, the
various options could be discussed in more detail in a future Note but the
JSON-LD spec seems to be the wrong place for this.

 

 

--

Markus Lanthaler

@markuslanthaler

 

 

 

 

From: Gregg Kellogg [mailto:gregg@greggkellogg.com] On Behalf Of Gregg
Kellogg
Sent: Friday, March 29, 2013 6:22 PM
To: Sandro Hawke
Cc: W3C RDF WG
Subject: Re: second review of json-ld

 

 

Gregg Kellogg

gregg@greggkellogg.net

 

On Mar 29, 2013, at 8:24 AM, Sandro Hawke <sandro@w3.org> wrote:





...


Alas, there is no defined way to merge RDF datasets.

The problem is that sometimes it's obvious that the merge of
    <g> { <a> <b> 1 }
and
    <g> { <a> <b> 2 }
is 
    <g> { <a> <b> 1,2 }
and sometimes it's obvious the two can't be merged because they contradict
each other.

See: http://www.w3.org/2011/rdf-wg/track/issues/17
RESOLVED: close issue-17 <http://www.w3.org/2011/rdf-wg/track/issues/17>  --
there is no general purpose way to merge datasets; it can only be done with
external knowledge. 

 

Proposed solution is to define it here, something like:  If multiple
embedded JSON-LD documents are extracted as RDF, the result is a dataset
formed by merging all the graphs that have the same name (and thus making a
single named graph per graph name) and all the default graphs (to make one
resulting default graph).

I discussed this on the GitHub issue tracker too.

 

We had a discussion on IRC about the problems of merging default graphs. For
example, if a developer re-states the facts in both RDFa and JSON-LD in the
same document (worse, microdata, which almost encourages the use of BNodes),
the result will be a merger with duplicate BNodes, that typically are
intended to be exactly the same node.

 

One way would be to provide an algorithm for creating a named graph to
contain the default graphs of all included script, microdata or RDF/XML
which is also extracted (another case where BNode graph IDs would have been
useful). Alternatively, a Note on the subject could just warn against this
pattern.

 

Alternatively, the result could simply be a set of graphs and datasets where
there is no defined merger, leaving it up to the application; however, I
don't find this very satisfying.

...

    -- Sandro

Gregg
Received on Friday, 29 March 2013 17:29:32 UTC

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