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Re: Annotation syntax [was: SPARQL* test suite]

From: Olaf Hartig <olaf.hartig@liu.se>
Date: Thu, 03 Sep 2020 10:04:47 +0200
To: public-rdf-star@w3.org
Cc: Holger Knublauch <holger@topquadrant.com>
Message-ID: <3320914.CqtZWCaAdk@porty3>
On torsdag 3 september 2020 kl. 13:14:27 CEST Holger Knublauch wrote:
> On 2/09/2020 23:17, Olaf Hartig wrote:
> > On onsdag 2 september 2020 kl. 13:55:46 CEST Andy Seaborne wrote:
> >> [...]
> >> I need to work though the details in your message but could I ask what I
> >> do wonder what the value of having the distinction in the formal model,
> >> compared with, say, a data design pattern "PG mode is SA where each
> >> referenced <<>> triple is also in the data graph".
> > 
> > The problem is that the assumption of which mode to use would not be
> > explicit in this case. For instance, if I put a Turtle* file online, your
> > client does not know whether I meant this to be considered in PG mode or
> > in SA mode. By using << .. >> exclusively for SA mode and {| ... |}
> > exclusively for PG mode, we can be explicit. My proposed formalism
> > carries over this distinction to the abstract data model.
> I very much support this idea of using the syntax to define a dialect.
> If I understand things correctly then PG mode is a subset of SA mode,
> i.e. the space of possible PG graphs is smaller than that of SA graphs.
> So I would assume that SA mode also still needs to allow << ... >>>
> syntax for the non-asserted triples. However, it seems that PG mode
> could be defined as the subset of SA that can be expressed through the
> {| notation, basically capturing what property graphs allow. This is
> probably another way of saying what Olaf has worked out with his more
> mathematical/formal spec?

Yes, you can certainly see it this way. The outlined formalism captures SA 
mode as a basis, and then adds PG mode on top as an option for the parts of 
your data for which you want to use it (which gives us a mixed-mode model in 
which we can explicitly use both modes within the same graph, just like in 
your proposed extension of Turtle*). Additionally, the formalism can be used 
a) to capture restrictions of the mixed-mode model to obtain a PG mode only 
version and b) to define mappings that represent everything in SA mode only.


> BTW, the use of triples as objects could be expressed using an inverse
> path, e.g.
> :bob :age 23 {| ^:disbelieves :alice |}
> although if Property Graphs don't support that then maybe RDF*'s PG mode
> also shouldn't.
> Holger
> > Olaf
Received on Thursday, 3 September 2020 08:05:08 UTC

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