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Re: How is RDF* supposed to work with Linked Data?

From: Holger Knublauch <holger@topquadrant.com>
Date: Wed, 5 Feb 2020 18:36:36 +1000
To: "public-rdf-star@w3.org" <public-rdf-star@w3.org>
Message-ID: <b4369a1d-63a1-254a-721b-bb684903bbfd@topquadrant.com>

On 5/02/2020 17:46, Olaf Hartig wrote:
> On onsdag 5 februari 2020 kl. 09:49:34 CET Holger Knublauch wrote:
>> On 5/02/2020 08:40, Martynas Jusevičius wrote:
>>> I don't see how RDF* can stay compatible with RDF:
>>>       A node may be a URI with optional fragment identifier (URI
>>>
>>> reference, or URIref), a literal, or blank (having no separate form of
>>> identification). Properties are URI references.
>>>
>>> https://www.w3.org/TR/rdf-concepts/#section-URI-Vocabulary
>> I share this concern. It is impractical to introduce a completely new
>> node type without breaking a lot of code and tools.
> In contrast. An advantage of the RDF*/SPARQL* approach is that supporting the
> approach in a system does not require the system to be rewritten such that it
> covers the RDF* data model internally. Instead, a small wrapper component on
> top of the unchanged system internals can do the trick. Such a wrapper may map
> RDF* data and SPARQL* queries into RDF and SPARQL by using, for instance, the
> RDF reification vocabulary (or any other explicit reification approach).
> Alternatively, the wrapper may implement a mapping to the URI reification
> approach that you mention.

Ok, granted. You are enumerating those two options at the end of

http://blog.liu.se/olafhartig/2019/01/10/position-statement-rdf-star-and-sparql-star/

I guess the second option - to change the data model and storage - is 
what Martynas was referring to, and what I agree doesn't easily work for 
our scenarios either.

OTOH, I agree that using Turtle* and SPARQL* as a syntactic layer is 
quite feasible and is the approach we are taking too. Needless to say 
these mapping approaches imply some compromises, e.g. if SPARQL* maps to 
rdf:Statements then queries need to take care not to accidentally also 
bump into the "physical" triples (rdf:object etc) that SPARQL* was 
supposed to hide.

Holger


>
> -Olaf
>
>   
>> This is why, at least for the time being, we are using what could be
>> considered a hack, encoding triples as URIs:
>>
>> http://datashapes.org/reification.html#uriReification
>>
>> No approach is ideal, but this here is the most incremental, realistic
>> route for us. The ugly long URIs would typically be hidden, e.g. behind
>> a syntax like Turtle* and SPARQL* which we are trying to implement for
>> our platform's next major release.
>>
>> (And yes, whether these long URIs should use namespace prefixes is
>> another open question which we may need to revisit).
>>
>> Holger
>
Received on Wednesday, 5 February 2020 08:36:43 UTC

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