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

From: David Booth <david@dbooth.org>
Date: Sat, 15 Jun 2013 16:30:51 -0400
Message-ID: <51BCCEFB.1030403@dbooth.org>
To: Pat Hayes <phayes@ihmc.us>
CC: public-rdf-comments <public-rdf-comments@w3.org>
excellent point. Thank you Pat.


On 06/15/2013 01:40 PM, Pat Hayes wrote:
> David
> I do not see any point in using a different suffix. The logic of
> skolemization is the same in both cases. There is no need to 'flag'
> an IRI to prevent it being made back into a bnode in a situation
> where it is in any case illegal to make it into a bnode. I think the
> use of another suffix encoding achieves nothing of value and is
> likely to produce confusion. For example, would it be an error to use
> a json-ld-genid (of gen-genid) skolem ID in a situation where it
> *would* be legal to replace it with a bnode? Therefore I suggest
> simply using genid for these skolemizations just like the others.
> Pat
> On Jun 13, 2013, at 12:09 PM, David Booth wrote:
>> The JSON-LD group would like input from the rest of the RDF Working
>> Group about skolemization.
>> During the last JSON-LD call
>> http://json-ld.org/minutes/2013-06-11/ there was discussion of a
>> proposal to require skolemization of JSON-LD blank nodes, when
>> interpreting JSON-LD as RDF, in cases where they otherwise would be
>> converted to RDF blank nodes but are used where a blank node is not
>> allowed in RDF.  (At present they are prohibited as predicates and
>> as graph names.)
>> The proposal was #1 at:
>> http://lists.w3.org/Archives/Public/public-rdf-comments/2013Jun/0072.html
>> 1. In RDF conversion algorithms in JSON-LD 1.0 Processing
>> Algorithms and API,
>> http://json-ld.org/spec/latest/json-ld-api/#rdf-conversion-algorithms
specify that **when JSON-LD is interpreted as RDF,** (i.e., when the
>> JSON-LD model is converted to the RDF model) skolem IRIs MUST be
>> generated using the well-known URI suffix "json-ld-genid" for any
>> JSON-LD blank node that would otherwise be mapped to an RDF blank
>> node in a position where an RDF blank node is not permitted.
>> Conversely, when RDF is serialized as JSON-LD (or when an RDF model
>> is converted to a JSON-LD model), skolem IRIs having the well-known
>> URI suffix "json-ld-genid" SHOULD be serialized as JSON-LD blank
>> nodes.  Finally, register the well-known URI suffix
>> "json-ld-genid", in accordance with RFC5785:
>> http://tools.ietf.org/html/rfc5785 BACKGROUND NOTE: The existing
>> well-known URI suffix "genid" is for converting to/from RDF blank
>> nodes (in positions where blank nodes are *permitted* in RDF),
>> whereas "json-ld-genid" will be used for *avoiding* blank nodes (in
>> positions where they are not allowed in RDF). ]]
>> There was also some follow up email discussion about what
>> well-known URI suffix to use, but that is probably a minor issue.
>> Before making a decision about this proposal, the JSON-LD group
>> would like to know whether others think this proposal is reasonable
>> and viable.  The goal is to make JSON-LD function more predictably
>> as a concrete RDF syntax.  At present, such skolemization is
>> optional, which means that a user cannot be assured of obtaining
>> legal RDF or knowing whether the otherwise-illegal triples will
>> simply be dropped.
>> Please let us know your thoughts.
>> Thanks, David
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Received on Saturday, 15 June 2013 20:31:19 UTC

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