Re: RDF*/SPARQL* syntax

Hi Richard,

On tisdag 3 september 2019 kl. 14:33:08 CEST Richard Cyganiak wrote:
> [...]
> >>>      << <<:a :b :c>> :d :e >> :f :g .
> >>> 
> >>> How would you represent this triple in the alternative serialization
> >>> syntax that you have outlined?
> >> 
> >> In my straw man syntax, this triple would be written as:
> >>    :a :b :c <<:d :e <<:f :g>> >>.
> > 
> > Mmh. While I understand how this would work, I think that expressions of
> > this form can be confusing as a serialization syntax for nested RDF*
> > triples. I mean, this expression also looks like something that is
> > nested, but the way this expression uses nesting is a very different one
> > from the notion of nesting of triples that we have in abstract syntax of
> > the RDF* data model.
>
> When you say this, you gloss over an important aspect of the RDF* data
> model: the fact that the notation "<<:a :b :c>> :d :e" in Turtle* expresses
> two triples, not one:
> 
>     ((:a :b :c) :d :e)
>     (:a :b :c)
> 
> If the notation would only express the former triple, then there would
> indeed be a clean and direct correspondence between concrete and abstract
> syntax.
> 
> But the notation also expresses the latter triple, and that aspect of the
> abstract syntax is not hinted at in the concrete syntax at all.
> In the alternative straw man syntax, one cannot write the expression for
> the composite triple without first writing the expression for its inner
> constituent triple:
>     :a :b :c <<:d :e>>
> 
> This makes quite obvious that the ":a :b :c" triple is part of the graph
> too.
> 
> In that sense, the nesting in the alternative syntax captures the constraint
> of the RDF* data model better than the nesting of Turtle*.

That's a very good argument!

However, the aspect of RDF* that you mention exists only when using RDF*/
SPARQL* in PG mode. It is not clear yet whether we end up with proposing only 
PG mode, or only SA mode, or maybe both as alternative options.

Thanks,
Olaf

Received on Tuesday, 3 September 2019 20:13:40 UTC